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Photo Forum / Digital Photography / DSLR Cameras / March 2006help with manual focus on Rebel XT
I was wanting longer focal lengths for my Canon Digital Rebel XT without spending a huge pile more money so I purchased two methods to compare. 1. A 2x teleconvertor to mount to my Canon EF 70-300mm F4-5.6 IS lens. 2. A Quantaray 500mm F8 mirror lens and nice solid T-Mount to EOS adaptor. 3. Crop the image and enlarge. So far solution 1 is producing slightly better results and the IS feature does work. However it becomes 140-600mm F8-11 lens and autofocus doesnt really work so it requires manual focus. Solution #2 is nice because it is so light weight and compact and is actually faster at 500mm F8. However it is manual focus, fixed aperture, no IS. I can live with those trade-offs, but I cannot get the focus quite on. The depth of field is very small so it has to be good. So far neither of the above is really getting significantly better results than cropping the image from the 70-300 with no TC. In both cases it seems like the focus is always a bit off. The 70-300 with TC is a bit sharper but still fairly poor. I am using a tripod and a RS60-E3 remote shutter release. My suspicion is that I don't have the eyepiece diopter quite perfectly adjusted and am misfocussing, or that the focus screen is not perfectly matched in distance as the image sensor. When the image on the focussing screen looks sharpest to me, the captured image is still a bit blurred. I am considering purchasing an eyepiece diopter to try to get the focussing screen completely sharp since I am at the end of the range on the camera. Is there a technique to getting really sharp manual focus or do I just need more practice? > I was wanting longer focal lengths for my Canon Digital Rebel XT without > spending a huge pile more money so I purchased two methods to compare. [quoted text clipped - 27 lines] > Is there a technique to getting really sharp manual focus or do I just need > more practice? Just one thing you could try: If you hold the shutter button half way down as you focus, the confirmation light will glow (and beep will sound if you have it enabled) when you achieve correct focus. Regards, Brian. >Just one thing you could try: If you hold the shutter button half way >down as you focus, the confirmation light will glow (and beep will sound >if you have it enabled) when you achieve correct focus. Focus confirmation only work under the aperture conditions in which AF works. You'd have to tape the contacts to make the TC invisible to accomplish that, but all your EXIF data will be wrong about FL and aperture. In any event, I find that even with no TC, focus confirmation is not all that accurate; for very shallow DOF, the confirmation is too liberal.  Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > Focus confirmation only work under the aperture conditions > in which AF works. You'd have to tape the contacts to make [quoted text clipped - 4 lines] > confirmation is not all that accurate; for very shallow > DOF, the confirmation is too liberal. I sure wish EXIF showed the as-focused distance! My Nikon 5700 didn't, either. My Canon 17-40 and 24-70 L-glass lenses both have distance scales like my old Nikon FTN Nikkor lenses did, but in a few quickie tests, I learned that it was showing 12, maybe 15 feet when the real distance by pacing it off or measuring with an 18' tape was closer to 25-30 feet. So, after about an hour, I gave up using the scale to tell me the distance for those rare occasions I want to use full manual on my 430EX external flash and full manual on the Rebel. If my brain is all fried on this stuff, please enlighten me. I am just as interested in an alternate focusing solution as the OP, albeit on completely different lenses. SignatureATM, aka Jerry > I sure wish EXIF showed the as-focused distance! My Nikon 5700 > didn't, either. It won't. The mechanics will vary from one brand to another, but for example, the Nikon "D" lenses, which report focus distance information to the camera, work in "zones". They don't report the exact distance, just one of about a dozen ranges of distances, which is good enough for the purposes the camera uses the information for. > My Canon 17-40 and 24-70 L-glass lenses both have distance scales > like my old Nikon FTN Nikkor lenses did, but in a few quickie tests, > I learned that it was showing 12, maybe 15 feet when the real distance > by pacing it off or measuring with an 18' tape was closer to 25-30 > feet. Those scales can be off, depending on the lens. Some zoom lenses don't hold focus over their zoom range, so the exact position can vary with the zoom; some types of lenses can vary based on the environment, which is why you sometimes see ones that focus past infinity (or past the infinity mark on the scale). > If my brain is all fried on this stuff, please enlighten me. I > am just as interested in an alternate focusing solution as the > OP, albeit on completely different lenses. Scream and yell at the manufacturers to provide proper focusing screens for digital SLRs. The lack thereof is the worst thing about the entire spectrum of digital cameras. SignatureJeremy | jeremy@exit109.com Today Jeremy Nixon commented courteously on the subject at hand >> I sure wish EXIF showed the as-focused distance! My Nikon >> 5700 didn't, either. [quoted text clipped - 5 lines] > about a dozen ranges of distances, which is good enough for > the purposes the camera uses the information for. Interesting. This is the first time I've seen this info. Thanks. I just wondered for the last several years why EXIF for everybody's camera was blank for distance focused. >> My Canon 17-40 and 24-70 L-glass lenses both have distance >> scales like my old Nikon FTN Nikkor lenses did, but in a [quoted text clipped - 8 lines] > see ones that focus past infinity (or past the infinity > mark on the scale). My "camera droid" gave me a couple of excellent tips for doing Tv, Av, and M using eTTL on my 430EX that eliminated more than 99 44/100 of the times I used to think full manual might be necessary, so I no longer care that my L-glass misses the distance by almost half, for whatever the reason. I enjoy learning the theory of things, but after awhile, the pragmatist in me takes over. >> If my brain is all fried on this stuff, please enlighten >> me. I am just as interested in an alternate focusing [quoted text clipped - 3 lines] > focusing screens for digital SLRs. The lack thereof is the > worst thing about the entire spectrum of digital cameras. As a presidential candidate once said "it's the economy, stupid", meaning that "it's the cost, stupid" why low-end or maybe even high-end DSLRs have less-than-optimal finders. That was one of the big things I liked about my old Nikon FTN - replaceable ground glass. I had at least a half-dozen for various purposes, but kept coming back to the one with a cross-hatch pattern that was designed for the Nikkor 35mm PC. My first digital had it, too, but I can live without it. When I asked about this when I first bought the camera, I was given the web sites for a couple of firms that can put in a better "ground glass", but the price and side-effect disadvantage out-weighed the benefits for me. So, as I indicated, I just take another shot or two when I notice the camera "hunting and fetching" trying to get a lock. That gives me a good clue it will blow it, at least a little. SignatureATM, aka Jerry > Interesting. This is the first time I've seen this info. > Thanks. I just wondered for the last several years why EXIF > for everybody's camera was blank for distance focused. Ironically, it's probably more likely to happen in a point-n-shoot model than an SLR anytime soon -- with SLRs we're already using lenses that can't provide the information, and there's nothing the camera can do about it. > As a presidential candidate once said "it's the economy, > stupid", meaning that "it's the cost, stupid" why low-end or [quoted text clipped - 4 lines] > cross-hatch pattern that was designed for the Nikkor 35mm PC. > My first digital had it, too, but I can live without it. Even without an interchangeable viewfinder, I'd pay good money right now for a Nikon J-type focusing screen, or a third-party screen of the same design (microprism dot, no split screen) for my D2x. Only no one wants to sell me one. I keep checking brightscreen.com, which sells that kind of screen, just not for my camera. I even emailed them about it and got a noncommittal response. I read over on dpreview where some people have taken focusing screens for the F6 and successfully cut them down to the right size and shape to work in a D2x. Unfortunately I have neither the tools nor the skill to do that. I'd pay someone to do it for me, though, and I posted as much there. > When I asked about this when I first bought the camera, I was > given the web sites for a couple of firms that can put in a > better "ground glass", but the price and side-effect > disadvantage out-weighed the benefits for me. By "side-effect" do you mean on metering? I honestly don't know how such a thing would affect metering, but it would be a bit of a bummer if it did much damage in that area. SignatureJeremy | jeremy@exit109.com Today Jeremy Nixon commented courteously on the subject at hand > By "side-effect" do you mean on metering? I honestly don't > know how such a thing would affect metering, but it would > be a bit of a bummer if it did much damage in that area. The one I was advised on, which I confirmed when I looked, was these guys, I think http://www.katzeyeoptics.com/cgi-bin/ccp51/cp-app.cgi?pg=store When I investigated, it confirmed my benefactor's advice by saying that the AF points would no longer be there, and possibly that some of the other finder info was also missing. Then, too, it is a $105 solution plus $50 to install it, and I have to pay the shipping both ways. So, I decided it wasn't worth a couple hundred to me and quickly learned to adapt to the Rebel's finder. For other reasons, I recently pulled out my old Nikon FTN. I discovered that my remembrences of how bright the finder was, even with a 50mm f/1.4, isn't what I saw last week. Yes, it certainly was brighter than my Rebel with an f/3.5-f/5 lens, and it was easier to focus, but not as much as my 20/20 hindsight told me it was. So, I gave up and am going on with my life, which is to "run what ya brung", the motto of the old street drag racers. SignatureATM, aka Jerry > Today Jeremy Nixon commented courteously on the subject at > hand [quoted text clipped - 11 lines] > saying that the AF points would no longer be there, and possibly > that some of the other finder info was also missing. Hmm, I'm looking at the Nikon replacement screens and it says nothing is disabled. It does say it messes up metering a little... only significantly when spot metering on a slow lens. I guess because the spot metering is in the center where the split prism interferes. Also it's possible to special order additional crop lines for 4/3 view as an example. Nothing available for a D200 yet. > Then, too, > it is a $105 solution plus $50 to install it, and I have to pay > the shipping both ways. So, I decided it wasn't worth a couple > hundred to me and quickly learned to adapt to the Rebel's > finder. And another $55 for the brightness coating. > For other reasons, I recently pulled out my old Nikon FTN. I > discovered that my remembrences of how bright the finder was, [quoted text clipped - 5 lines] > So, I gave up and am going on with my life, which is to "run > what ya brung", the motto of the old street drag racers. SignaturePaul Furman http://www.edgehill.net/1 Bay Natives http://www.baynatives.com Today Paul Furman commented courteously on the subject at hand >>>By "side-effect" do you mean on metering? I honestly >>>don't know how such a thing would affect metering, >> The one I was advised on, which I confirmed when I looked, >> was these guys, I think [quoted text clipped - 6 lines] >> possibly that some of the other finder info was also >> missing. > Hmm, I'm looking at the Nikon replacement screens and it > says nothing is disabled. It does say it messes up metering [quoted text clipped - 5 lines] > for 4/3 view as an example. Nothing available for a D200 > yet. Threads have a life of their own, but I qualified my comment as Rebel XT-specific. I have zero.zero knowledge of Nikon DSLRs, except what I learned making my buy decision two months ago. SignatureATM, aka Jerry >> By "side-effect" do you mean on metering? I honestly don't >> know how such a thing would affect metering, but it would [quoted text clipped - 4 lines] > > http://www.katzeyeoptics.com/cgi-bin/ccp51/cp-app.cgi?pg=store Yeah, that's the one I saw too. If the effect on metering is deterministic, I'll live with it; I can adjust my meter once and be done with it. This is, of course, dependent on the camera you use; mine has the ability to adjust the meter, independently for each mode, in 1/6 stop increments. Unfortunately, they don't make the kind of screen I want. I know I'm in a small minority but I'm not a big fan of the split-image rangefinder. > When I investigated, it confirmed my benefactor's advice by > saying that the AF points would no longer be there, and possibly > that some of the other finder info was also missing. That, too, would be an issue. The AF points would still be there with my camera, along with everything else; that stuff is on a different "layer". > Then, too, it is a $105 solution plus $50 to install it, To me, though, that part isn't an issue. I'd be happy to pay that for a good focusing screen at this point. (I wouldn't need installation, either, with my camera, but still.) SignatureJeremy | jeremy@exit109.com Today Jeremy Nixon commented courteously on the subject at hand [snip] > Unfortunately, they don't make the kind of screen I want. > I know I'm in a small minority but I'm not a big fan of the > split-image rangefinder. I never liked the Nikon split image, either. I wasn't all that fond of microprism aids. If Nikon had sold an angled split image, I would've used that. So, I just trained myself to use a ground glass. But, for all the reasons I and the OP have discussed, that is grossly impractical on a Rebel with the slow lenses we now have. Now, as to slowness, it is a price I will happily pay for superier quality zoom lenses that are far more convenient as well as an overall cost savings. >> When I investigated, it confirmed my benefactor's advice >> by saying that the AF points would no longer be there, and [quoted text clipped - 11 lines] > wouldn't need installation, either, with my camera, but > still.) If I had a pro Nikon or Canon, and was either a pro or very serious amatuer, I'd do $200, but not at the Rebel's price point. But, as I am sure I will accumulate more Canon glass, filters (them are huge!), accessories, etc., it is virtually certain that my next camera will be a more expensive, more capable Canon. And, then, I would replace the finder if it hasn't been "fixed" by then. Interesting discussion we have here. I've enjoyed it immensely. And, no flames. Neat! SignatureATM, aka Jerry >> Focus confirmation only work under the aperture conditions >> in which AF works. You'd have to tape the contacts to make [quoted text clipped - 18 lines] > am just as interested in an alternate focusing solution as the > OP, albeit on completely different lenses. Excuse my absolute ignorance in this area, but... The sensor in the Rebel XT is supposedly 1.6X normal film equivalent, isn't it? A 300mm lens would actually result in 480mm? And an indicated lens focus distance of 15' would really be 24', wouldn't it? dwight (No answers... just lots of questions) >Excuse my absolute ignorance in this area, but... The sensor in the Rebel XT >is supposedly 1.6X normal film equivalent, isn't it? >A 300mm lens would actually result in 480mm? >And an indicated lens focus distance of 15' would really be 24', wouldn't >it? If you normally think in terms of 35mm, one way to think about the "crop factor" is to think of a 35mm image. Your camera is showing you 1/1.6 of that image. It is as if it had cropped the picture down to that size. Nothing else has changed. The f/stop, the focus distance, etc., are all as before. It is just that you are getting a crop of what you'd get if you used a 35mm film camera at the same position with the same focus, f/stop, and shutter speed. There is nothing magical about it. If you were used to 2 1/4 x 2 1/4 and switched to 35mm, you'd be "cropping" your images relative to what you were used to. ---- Paul J. Gans Today Paul J Gans commented courteously on the subject at hand > If you normally think in terms of 35mm, one way to think > about the "crop factor" is to think of a 35mm image. Your > camera is showing you 1/1.6 of that image. It is as if it > had cropped the picture down to that size. For me, the biggest mindset change was mentally calculating the 3:2 aspect ratio of my Rebel to the 4:3 I want to save JPGs at for my PC monitor. I did some simple test shots to "calibrate" the amount I needed to zoom out or stand farther back in order not to cut off something and everything is A-OK now. > Nothing else has changed. The f/stop, the focus distance, > etc., are all as before. It is just that you are getting a [quoted text clipped - 7 lines] > > ---- Paul J. Gans SignatureATM, aka Jerry > For me, the biggest mindset change was mentally calculating the > 3:2 aspect ratio of my Rebel to the 4:3 I want to save JPGs at > for my PC monitor. I did some simple test shots to "calibrate" > the amount I needed to zoom out or stand farther back in order > not to cut off something and everything is A-OK now. I was glad to find a camera with a 3:2 aspect ratio so that none of the megapixels would be wasted in getting standard 4x6" prints made. For the PC, I either have to crop or put black bands on the top and bottom. The Rebel XT was my first digital camera though so I never got used to 4:3 for pictures. It always seemed odd to me that many common picture sizes (3.75x5, 5x7, 8x10 etc) didn't match the ratio 36x24 of the negative frame. I always wondered what else was supposed to be in the frame that got chopped. Who decided the crop? Was it just centered or does the lab techician look at each one and find the best crop? At least with digital, I can choose my own crop before taking the files to the photolab for prints. Today default commented courteously on the subject at hand >> For me, the biggest mindset change was mentally >> calculating the 3:2 aspect ratio of my Rebel to the 4:3 I [quoted text clipped - 9 lines] > first digital camera though so I never got used to 4:3 for > pictures. There is no "right" answer to aspect ratio, I'm afraid. Your use and mine are different and we do what is best of us. > It always seemed odd to me that many common picture sizes > (3.75x5, 5x7, 8x10 etc) didn't match the ratio 36x24 of the > negative frame. I always wondered what else was supposed > to be in the frame that got chopped. Who decided the crop? > Was it just centered or does the lab techician look at each > one and find the best crop? But, these sizes were created literally from the cut film of the day, like 4x5 you left out. 35mm came from the movie industry, where an early form of "wide screen" was desired as was more analog "mega pixels", the same way 70mm is used or the really huge IMAX "film". Back when I did 35mm negs and prints and/or printed my slides, I had to be very aware of the aspect ratio at the time I shot, just like now, else something would get cut off by the finisher and/or it would be skinny across one axis of the print. Nothing has changed since Mathew Brady. Paper for computer printers have modern sizes, including metric, and modern aspect ratios. Film paper still uses the tradition measures, as does paper used by custom labs to the photographic numbers, so that customers can take prints made from digital to a framer and get 8x10, 11x14, or 16x20, which are all about 4:5, even "fatter". > At least with digital, I can choose my own crop before > taking the files to the photolab for prints. That is indeed the big advantage. So, I /always/ allow 15-20%, sometimes more, to not only allow for print cropping, but so that there's room to correct perspective "distortion" and improve the compusure through a more careful crop. SignatureATM, aka Jerry > Nothing has changed since Mathew Brady. Paper for computer > printers have modern sizes, including metric, and modern [quoted text clipped - 11 lines] > that there's room to correct perspective "distortion" and > improve the compusure through a more careful crop. This was an eye-opener, when I moved up from the S1 IS. The S1 captured images that translated directly to the monitor. The Rebel's aspect almost always means that the sides of each image will be cropped. At home, I have a standard 1024x768 LCD; at work, 1280x1024. We just picked up a widescreen notebook, too, with a 1280x800 setting. An image that looks great on my home screen needs to be cropped left and right to fit my work screen. That needs further cropping, if used on the notebook. The answer, then, seems to be to make sure that my subject fits vertically - horizontal be damned. The XT gives me excellent prints. But the most usual print sizes (5x7, 8x10) now dictate that I crop off a good portion of the image. Now, when I take photos, I have to plan ahead. I have to allow plenty of cropability, depending upon what I plan to do with them...? dwight (my brain hurts) Today dwight commented courteously on the subject at hand >>> At least with digital, I can choose my own crop before >>> taking the files to the photolab for prints. [quoted text clipped - 13 lines] > 1280x1024. We just picked up a widescreen notebook, too, > with a 1280x800 setting. The "correct" number for 4:3 is 1280 x 960. 1024 is too fat and 800 is way too skinny - in fact it is 8:5. Try to standardize them to the same aspect ratio, whatever floats your boat, if you can. It'll be less confusing. > An image that looks great on my home screen needs to be > cropped left and right to fit my work screen. That needs > further cropping, if used on the notebook. The answer, > then, seems to be to make sure that my subject fits > vertically - horizontal be damned. Just what I said above. Some monitors do a bullshit stretch in one direction which is horrid for image accuracy. > The XT gives me excellent prints. But the most usual print > sizes (5x7, 8x10) now dictate that I crop off a good > portion of the image. Again, I make damn well sure when I'm cropping to my standard 4:3, whether it be 1280x960, 1400x1050, or 1600x1200, my fav 3, I leave enough width on a landscape crop to be able to change to 3:2 for 4x6 and to 5:4 for 8x10. PSP has crop "presets" for all the common English and metric paper sizes and if you're missing one, it can be quickly created. e.g., I have one to give me a starting point on my Rebel pics at either 4 or 8 MP. > Now, when I take photos, I have to plan ahead. I have to > allow plenty of cropability, depending upon what I plan to > do with them...? Yes, dwight. Remember the 6 P Principle, it works: "Proper Planning Prevents Piss Poor Performance." And, another one that fits is "never give Murphy an even break." If you're going to fook something up, exposure, composure, or cropping, it /will/ be when you're shooting a rare species of animal with your longest lens at a 1/2 away and there's only 1 second before the animal bolts. SignatureATM, aka Jerry > Today dwight commented courteously on the subject at hand > [quoted text clipped - 20 lines] > standardize them to the same aspect ratio, whatever floats > your boat, if you can. It'll be less confusing. 1600x1200 = 1024X768 = 800X600, relatively speaking. But 1280X1024 is the off size in the bunch. I don't "stretch" my wallpaper, I custom tailor it. >> An image that looks great on my home screen needs to be >> cropped left and right to fit my work screen. That needs [quoted text clipped - 4 lines] > Just what I said above. Some monitors do a bullshit stretch in > one direction which is horrid for image accuracy. I resize my images to fit the screen. I don't let the screen resize my images. >> The XT gives me excellent prints. But the most usual print >> sizes (5x7, 8x10) now dictate that I crop off a good [quoted text clipped - 8 lines] > have one to give me a starting point on my Rebel pics at > either 4 or 8 MP. I just had some digitals printed out last Christmas, my first time. Quite an eye-opener, for someone who never really gave it much thought. From my 3MP camera, I was still able to crop out the crap and have plenty of data left for a good 4X6 print. But it was iffy in some cases. With the 8MP Rebel, I now have PLENTY of room to work with. I always shoot at best quality (largest image), which translates to 11.5 X 7.67 in a 300dpi print. Now I can go 5X7, or 8X10, and still frame the shot I want (not necessarily the shot I took). >> Now, when I take photos, I have to plan ahead. I have to >> allow plenty of cropability, depending upon what I plan to [quoted text clipped - 7 lines] > with your longest lens at a 1/2 away and there's only 1 second > before the animal bolts. Amen to that! I used to curse the S1's two-second startup time. Missed a few great opportunities there. I haven't had the excuse to "whip out" the Rebel, but that 1/2-second from OFF to SHOOT was a huge selling point for me. (Of course, that 1/2 second doesn't take into account my fumbling with the lens cap, checking the shooting mode, forgetting to set the lens back to auto focus, or finding out that the battery doesn't have enough juice left to fire the flash.) dwight Today dwight commented courteously on the subject at hand > 1600x1200 = 1024X768 = 800X600, relatively speaking. But > 1280X1024 is the off size in the bunch. I don't "stretch" > my wallpaper, I custom tailor it. Definitely. Some people, I suppose, run wallpaper or screensavers with images of the different aspect ratios and avoid stretching, and some are now going to the new wide monitors to also be able to view cable HDTV. > I just had some digitals printed out last Christmas, my > first time. Quite an eye-opener, for someone who never [quoted text clipped - 6 lines] > 5X7, or 8X10, and still frame the shot I want (not > necessarily the shot I took). This is facilitated by allowing 20-25% more around the main subject than "cropping tight" would usually tell you do do. With even a moderate MP size, it is trivial to crop in the digital darkroom, plus it has the advantage of seeing the full-size image which allows you to be more creative. > Amen to that! I used to curse the S1's two-second startup > time. Missed a few great opportunities there. I haven't had [quoted text clipped - 5 lines] > out that the battery doesn't have enough juice left to fire > the flash.) "A fool and his spare time are soon parted." <grin> Don't keep changing all that stuff from one shot to another and you won't "forget." And, why do you want to shut the camera down between shots in the first place? My Rebel starts back up from hibernation far faster than my now broken Nikon 5700 (it died and I literally fixed it with a hammer, good riddance to bad garbage). Even so, I changed the power down time to 30 minutes once I discovered that unlike an EVF that eats batteries, I can usually get 400-500 pictures, sometimes 600 or more on one battery. I always use my Canon 430EX external flash so I'm not chewing up precious battery power on flash, either. I don't put the lens cap on in the field. It isn't just for quick photo ops, it is just a bother when taken many hundreds of images in a few hours, such as at a museum or outside show, and you're trying to do crowd control by prefocusing and waiting patiently for the gawkers to walk away. I understand but am still highly annoyed when people intentionally walk right in front of somebody about ready to take a picture, stand right in front of the subject, and dawdle. Kids are notorious for that, they do it intentionally. So, to avoid me being rude and causing the kids to stay put to annoy /me/, I just go someplace else and take a few shots until they leave. I shoot mainly cars, and unlike many folks, seldom have distracting people in my pictures even in the background. I don't have to be obnoxious or even ask people to step aside. I just wait patiently with the camera /down/ until they walk off. SignatureATM, aka Jerry > > Nothing has changed since Mathew Brady. Paper for computer > > printers have modern sizes, including metric, and modern [quoted text clipped - 29 lines] > Now, when I take photos, I have to plan ahead. I have to allow plenty of > cropability, depending upon what I plan to do with them...? So you never used 35mm film? Greg >> > Nothing has changed since Mathew Brady. Paper for computer >> > printers have modern sizes, including metric, and modern [quoted text clipped - 35 lines] > > Greg Far too much. Film is the reason I went digital. dwight > >> > Nothing has changed since Mathew Brady. Paper for computer > >> > printers have modern sizes, including metric, and modern [quoted text clipped - 39 lines] > > dwight And what's the aspect ratio of 35mm film? Greg >> >> Now, when I take photos, I have to plan ahead. I have to allow plenty > of [quoted text clipped - 11 lines] > > Greg I usually look at it flat. Either on a table or held up in front of me. dwight >>>>>Now, when I take photos, I have to plan ahead. I have to allow plenty >> [quoted text clipped - 15 lines] > > I usually look at it flat. Either on a table or held up in front of me. Did you ever notice it's 2x3 just like these new fangled DSLRs that you and Mopar are so surprised about? Greg Signature"All my time I spent in heaven Revelries of dance and wine Waking to the sound of laughter Up I'd rise and kiss the sky" - The Mekons >>>>>>Now, when I take photos, I have to plan ahead. I have to allow plenty >>> [quoted text clipped - 20 lines] > > Greg Oh, I don't think "surprised" is the right term. Yes, I used to have many, many a poor shot developed and printed on standard 4X6 prints. Now I can develop my own and print on 4X6 prints. I come to the Rebel XT from the S1, which gave me 4.5X6... So, while not "surprised", more like "slow to pick up." Yeah, that's it. And, when I said that film was the reason I went digital, I didn't mean that I threw away all of my film cameras, never to return. I was hoping that using the "free film" of a fully-functional digital camera would help me BETTER my film use. I've spent thousands over the years for film prints that always "surprised" me, usually in the negative. Playing with digital ISO, aperture, "shutter speed", etc etc etc and NOT paying to have the results printed before I see them will, I sincerely hope, allow me to better prepare my shots with, say, my Pentax ZX-M. At least, that's why I'm spending thousands over THESE years. dwight Today dwight commented courteously on the subject at hand > Excuse my absolute ignorance in this area, but... The > sensor in the Rebel XT is supposedly 1.6X normal film > equivalent, isn't it? > > A 300mm lens would actually result in 480mm? Yes, it is. A Nikon D70 is 1.5, IIRC. > A 300mm lens would actually result in 480mm? Yes. So, my 24-70mm is the equivalent of about 38-112. But, I'm slowly learning to change my mind set about this and think in terms of the real focal length, and not equivalents. > And an indicated lens focus distance of 15' would really be > 24', wouldn't it? Hmmm. Never thought of that! I do believe you've got it! Same lens fits a full-frame film cameras, if any. I remember pacing off the distance in the store in my family room, and verified it att home with my 18' Stanley. I just didn't make the connection you did. Isn't Canon's new $4K 5D it's first full-frame DSLR? > dwight > (No answers... just lots of questions) Keep asking, Dwight! I just learned a "can't see the forest for the trees" object lesson here. Thanks, muchly. SignatureATM, aka Jerry >> And an indicated lens focus distance of 15' would really be >> 24', wouldn't it? [quoted text clipped - 4 lines] > att home with my 18' Stanley. I just didn't make the connection > you did. I don't think the sensor size makes any difference to the image being in focus for a given subject distance. The image is simply cropped. The lens has the same focal length, the subject distance is the same for a given focus ring position because the rear focal length has not changed either. The sensor to focal point distance is the same. The image is sharp at the same point and cropping does not change this, so the distance ring is simply wrong on your lens for any sensor size. I have also found my lenses are not accurate for distance. >>>And an indicated lens focus distance of 15' would really be >>>24', wouldn't it? [quoted text clipped - 7 lines] > I don't think the sensor size makes any difference to the image being in > focus for a given subject distance. There is deeper DOF with a smaller sensor. > The image is simply cropped. The lens > has the same focal length, the subject distance is the same for a given [quoted text clipped - 3 lines] > wrong on your lens for any sensor size. I have also found my lenses are not > accurate for distance. Today Paul Furman commented courteously on the subject at hand > There is deeper DOF with a smaller sensor. That's a real issue for me when shooting flash in museums. DOF is always a concern to keep shutter speeds up to prevent shake and keep ISO down to minimize noise, hence I have to be careful where on a 3/4 view of a car I choose to lock the focus, the general subject of this thread. Like everything in life, DOF vs. shake vs. noise is a trade-off for which there is no right answer fits all deal. SignatureATM, aka Jerry >There is deeper DOF with a smaller sensor. ... because you're using a shorter real, absolute focal length to obtain the same angle of view. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >Excuse my absolute ignorance in this area, but... The sensor in the Rebel XT >is supposedly 1.6X normal film equivalent, isn't it? [quoted text clipped - 3 lines] >And an indicated lens focus distance of 15' would really be 24', wouldn't >it? No. It's just like a crop of 35mm film, 1/1.6 the width and height. Does cropping film affect focusing distance? It's generally better than cropping 35mm film, though, as such a crop of film would have less resolution, with most films, especially high-speed films. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >>Just one thing you could try: If you hold the shutter button half way >>down as you focus, the confirmation light will glow (and beep will sound >>if you have it enabled) when you achieve correct focus. > > Focus confirmation only work under the aperture conditions in which AF > works. The focus confirmation light on my D70 seems to work fine at large f/stop numbers. > You'd have to tape the contacts to make the TC invisible to > accomplish that, but all your EXIF data will be wrong about FL and > aperture. > > In any event, I find that even with no TC, focus confirmation is not all > that accurate; for very shallow DOF, the confirmation is too liberal. I agree it's not very accurate. What I do is rock back & forth to find the sweet spot in the middle. It helps a lot to have a nice smooth, slow focus ring action which is not the case on many AF zooms. >> Focus confirmation only work under the aperture conditions in which AF >> works. >The focus confirmation light on my D70 seems to work fine at large >f/stop numbers. Minimum f-stop for the lens, or currently selected f-stop? Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >>>Focus confirmation only work under the aperture conditions in which AF >>>works. [quoted text clipped - 3 lines] > > Minimum f-stop for the lens, or currently selected f-stop? I'm not sure what you are asking. I tried it at f/20 in a dark room and it worked. It goes up to f/22, it was a 6 second exposure. >>>The focus confirmation light on my D70 seems to work fine at large >>>f/stop numbers. >> Minimum f-stop for the lens, or currently selected f-stop? >I'm not sure what you are asking. I tried it at f/20 in a dark room and >it worked. It goes up to f/22, it was a 6 second exposure. IU was asking if you meant high-f-stop shots came out focused as desired, or if you were referring to slow lenses. What you replied now is something I would take for granted. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >>>>The focus confirmation light on my D70 seems to work fine at large >>>>f/stop numbers. [quoted text clipped - 8 lines] > > What you replied now is something I would take for granted. Oh yes, sorry, I was mistaken. That was on an f/2.8 lens and it doesn't matter what I set the aperture to. Nevermind. > Just one thing you could try: If you hold the shutter button half way down > as you focus, the confirmation light will glow (and beep will sound if you > have it enabled) when you achieve correct focus. Thanks Brian. Actually focus confirmation for manual focussing only works on autofocus lenses. A manual focus lense won't actuate the focus confirmation light. The confirmation light does work for the 70-300 IS lens when it is on the 2x TC but only out to F8 (if it is a bright and contrasty scene, F5.6 if not) so I lose this feature before I get over 300mm. This leaves manual focus without confirmation as the only option. Of course for the 500mm mirror, it is always this way as it is a MF lens. >>Just one thing you could try: If you hold the shutter button half way down >>as you focus, the confirmation light will glow (and beep will sound if you [quoted text clipped - 4 lines] > Actually focus confirmation for manual focussing only works on autofocus > lenses. A manual focus lense won't actuate the focus confirmation light. This is not true on a Nikon D70. > The confirmation light does work for the 70-300 IS lens when it is on the 2x > TC but only out to F8 (if it is a bright and contrasty scene, F5.6 if not) > so I lose this feature before I get over 300mm. This leaves manual focus > without confirmation as the only option. Of course for the 500mm mirror, it > is always this way as it is a MF lens. >> Actually focus confirmation for manual focussing only works on autofocus >> lenses. A manual focus lense won't actuate the focus confirmation light. > > This is not true on a Nikon D70. That is very cool and helpful. I wish Canon had included that feature. I considered the D70 when I purchased the Rebel XT but I liked the smaller size and weight of the Canon and the control placements. I was concerned that a larger and heavier camera would cause me to leave it at home more and the smaller camera might get more use. With the battery grip removed, and an EF 50mm F/1.8 II or the EF-S 18-55mm, the camera is quite light and small. > "Paul Furman" <paul-@-edgehill.net> wrote > [quoted text clipped - 11 lines] > an EF 50mm F/1.8 II or the EF-S 18-55mm, the camera is quite light and > small. I have one MF prime lens & I depend on the AF confirm to use that. It's still a pain though with lots of misses. The Rebels are good cameras, whatever feels good. Today Paul Furman commented courteously on the subject at hand >>>Just one thing you could try: If you hold the shutter >>>button half way down as you focus, the confirmation light >>>will glow (and beep will sound if you have it enabled) >>>when you achieve correct focus. >> Actually focus confirmation for manual focussing only >> works on autofocus lenses. A manual focus lense won't >> actuate the focus confirmation light. > > This is not true on a Nikon D70. I only got involved in this thread because the OP said he had a Rebel XT. So, aside from interest, what does it matter what a D70 can do, except as lurkers with them might benefit from the general discussion? SignatureATM, aka Jerry > Actually focus confirmation for manual focussing only works on autofocus > lenses. A manual focus lense won't actuate the focus confirmation light. I have seen somebody selling a bit of plastic with contacts supposedly enabling the focus confirmation with EOS. No idea if they work, how they work and if they are worth anything. -Wolfgang > Just one thing you could try: If you hold the shutter button half way > down as you focus, the confirmation light will glow (and beep will sound > if you have it enabled) when you achieve correct focus. It's been years since I've relied on the "focus confirmation" light, probably becasue it was the worst way to assure sharp focus ... but I really don't remember why I don't even look at it... Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. Today Brian commented courteously on the subject at hand >> Is there a technique to getting really sharp manual focus >> or do I just need more practice? [quoted text clipped - 3 lines] > will glow (and beep will sound if you have it enabled) when > you achieve correct focus. Brian, please see my comments to the OP that I posted before I read yours. I imagine the OP has already learned to do this. I've known to do that all the time since my first digital 5 years ago. To start with, the out-of-the-box setting for AF on a Rebel is to use all 8 of 8 possible sampling points. A red dot flashes briefly in the viewfinder to show which and how many points were used in the calculation. It didn't take me long to figure out that for car pictures, my primary interest, 2, 3, 4 AF points results in wildly inaccurate AF because it is trying to do some artificial intelligence trick and gets easily confused. So, I turned all that off in favor of just one AF point in the center, the same one I use separately for AE lock or FEL lock. I quickly dropped from 10-15% out-of-focus to 1%, sometimes 2% of the pictures in any given "shoot". About half of my pictures are in museums with available light or flash, and the rest in daylight, so the challenges of getting a good AF lock are completely different, and it is much more difficult to focus manually in dim museum lighting. SignatureATM, aka Jerry Today default commented courteously on the subject at hand > I was wanting longer focal lengths for my Canon Digital > Rebel XT without spending a huge pile more money so I > purchased two methods to compare. I have 4 lenses for mine, kit lens, 17-40 L zoom, 24-70 L, and a Sigma 18-125. I have great difficulty getting a decent AF lock, even after reducing the sampling points to only one in the center. About 1-2% of what I shoot are just a tad out-of- focus. And, no, it isn't shake. So, I've learned to take a 2nd shot with the AF point moved slightly if there is any doubt at all in my mind. Digital is free, the battery lasts me for over 400 exposures, and alkaline AAs last 200+ in my Canon 430EX external. Since I shoot either large or medium JPEG, 2 1/2 gig of memory with me is plenty. So, I've also experimented with MF as well. But, it is also problematical and inaccurate for me, quite probably because the "finder" has no optical focus aide such as split image or microprism, and is 4 stops dimmer than my old Nikon FTN going from a 50mm f/1.4 prime to an average f/2.8-5.6 on the Rebel, depending on lense and zoom focal length used. Plus, the Rebel's AF/AE system refuses to show me an AE lock in manual focus mode unless /it/ thinks I've correctly got the blinking thing in focus. So, if I could get 100.0% AF lock on auto, why the hell would I try manual? And, if /my/ version is what I want, good, bad, or indifferent, how can I convince the Rebel to still do an AE lock? Yes, I've tried the 4 ways that AE/AF can be set as a custom function by reading/re- reading/re-reading - RTFM, right? Also experimented, also talked to my local camera store manager, who is at least marginally good at this stuff. So, I posted near the top because I cannot at all help you in your particular endeavor, except to say that neither of us are going goofy - or we both already are, but don't know it. Good luck, and please, please, please post what you finally find as a good solution, and I will try to duplicate your success with my lenses and workflow. > 1. A 2x teleconvertor to mount to my Canon EF 70-300mm > F4-5.6 IS lens. 2. A Quantaray 500mm F8 mirror lens and [quoted text clipped - 30 lines] > Is there a technique to getting really sharp manual focus > or do I just need more practice? SignatureATM, aka Jerry > Today default commented courteously on the subject at hand > I have 4 lenses for mine, kit lens, 17-40 L zoom, 24-70 L, and > a Sigma 18-125. I have great difficulty getting a decent AF [quoted text clipped - 6 lines] > external. Since I shoot either large or medium JPEG, 2 1/2 gig > of memory with me is plenty. I often limit which point is used also, because sometimes it switches focus points from a little wiggle of the camera, and you end up with the wrong thing in focus if you let it choose. I only shoot raw, sometimes raw+jpg because I find I often want to adjust the exposure or white balance a little even if everything else is good and raw makes it so easy. 2GB cards are now less than $99 so storage space is hardly an issue. Raw+JPG is good for when you want to stop at the photolab for a few prints and not have to go home to use the computer to convert them. > So, I've also experimented with MF as well. But, it is also > problematical and inaccurate for me, quite probably because > the "finder" has no optical focus aide such as split image or > microprism, and is 4 stops dimmer than my old Nikon FTN going > from a 50mm f/1.4 prime to an average f/2.8-5.6 on the Rebel, > depending on lense and zoom focal length used. I am suspecting that I might need a negative diopter eyepiece to get the viewfinder really sharp to be able to manual focus accurately. I'm going to order one next week and see if it helps. > Plus, the Rebel's AF/AE system refuses to show me an AE lock > in manual focus mode unless /it/ thinks I've correctly got the > blinking thing in focus. So, if I could get 100.0% AF lock on > auto, why the hell would I try manual? Sometimes the autofocus hunts and overshoots and misses the right spot. If you switch to manual, you can focus more slowly and get it right. The AF confirmation is nice for this. And, if /my/ version is > what I want, good, bad, or indifferent, how can I convince the > Rebel to still do an AE lock? Yes, I've tried the 4 ways that > AE/AF can be set as a custom function by reading/re- > reading/re-reading - RTFM, right? Also experimented, also > talked to my local camera store manager, who is at least > marginally good at this stuff. I just tried it with my Rebel XT and it will happily take an out of focus picture with AE lock. I put it to manual focus, pointed it at a bright source with the focus way off, pressed *, (the * indicator lit), recomposed and then fired off a very out of focus and underexposed shot. This was in Av mode with all CFn's set to 0 (defaults). Maybe yours needs a firmware update? > So, I posted near the top because I cannot at all help you in > your particular endeavor, except to say that neither of us are [quoted text clipped - 3 lines] > find as a good solution, and I will try to duplicate your > success with my lenses and workflow. The goofy thing might be expecting a sharp image from an inexpensive solution. I am coming to the conclusion that the Quantaray 500mm F/8 mirror may never focus really sharp. It is light, small, inexpensive, fully coated and has correction optics, but it just isn't so sharp. I can get an acceptable picture for viewing on a computer screen by reducing the 8MP original down to 800x533 or smaller and then a bit of unsharp mask. I don't think it will make a decent print at 4x6 at all. With practice now I can get pretty sharp with the Canon EF 70-300mm F4-5.6 with a Quantaray 2x teleconvertor, but between 500 and 600mm I am getting a somewhat soft image, not nearly as sharp as without the TC, but I still think some of the problem is in focussing techique because I can't get as sharp manual focussing with no TC as the AF gives. I am using a tripod, remote shutter switch, and mirror lock-up, but still I am sure I can do better. The eventual solution might be to learn to live with only a 300mm focal distance and crop somewhat for smaller prints. Even cropping out 4 of the 8 MP still gives a nice 4x6" print while increasing the apparent focal distance a lot. Today default commented courteously on the subject at hand > I often limit which point is used also, because sometimes > it switches focus points from a little wiggle of the > camera, and you end up with the wrong thing in focus if you > let it choose. I should have mentioned, but didn't think of it until now, but the method(s) one chooses to use for AF are highly dependent on the subject type. e.g., it is one thing to keep a pet in focus when they're jumping around, as my daughter's Chiuaua was last night, and quite another for me shooting cars in available light or with flash. Likewise, if one is shooting only scenics at a distance, you just set the focus to infinity and shoot. Obviously, that can't work for you with the long lenses you want to use, else you'd not have posted in the first place. > I only shoot raw, sometimes raw+jpg because I find I often > want to adjust the exposure or white balance a little even [quoted text clipped - 3 lines] > photolab for a few prints and not have to go home to use > the computer to convert them. I can do RAW+JPEG but I'm too new at the DSLR game to have even loaded the Canon RAW converter. But, I intend to learn later this spring, after I'm done spending money. > I am suspecting that I might need a negative diopter > eyepiece to get the viewfinder really sharp to be able to > manual focus accurately. I'm going to order one next week > and see if it helps. A Rebel has what, 6 or so diopter setting built in. I set it 1 or 2 from one end if I'm wearing my reading glasses so I can see various small text as I change photometrics as I shoot, and 1 or 2 from the other end if I'm outdoors and don't need to play with the camera, just shoot. I tested what I thought I was seeing against the image that resulted and concluded how to set the diopter so I can at least try to get the AF right. >> Plus, the Rebel's AF/AE system refuses to show me an AE >> lock in manual focus mode unless /it/ thinks I've [quoted text clipped - 6 lines] > slowly and get it right. The AF confirmation is nice for > this. Yes, but that's not what I'm talking about here. The Rebel wants me to twiddle the focus ring until I see the red dot come on, then it shows the green dot for AE and AF. If I believed the AF, why the hell am I even trying manual? Same for you, I suspect. > And, if /my/ version is >> what I want, good, bad, or indifferent, how can I convince [quoted text clipped - 11 lines] > was in Av mode with all CFn's set to 0 (defaults). Maybe > yours needs a firmware update? Yes, you can intentionally take it out. I'm talking about the old-fashioned way to do it - shift the ring out, move it fairly quickly in the direction it needs to go, and stop when it looks sharp. On my Canon, the bullshit AF that I can't shut off overshoots, so I'm toast. > The goofy thing might be expecting a sharp image from an > inexpensive solution. I am coming to the conclusion that [quoted text clipped - 5 lines] > then a bit of unsharp mask. I don't think it will make a > decent print at 4x6 at all. The kit lens is a tad soft for what I do, but I didn't expect much out of an 18-55 that only costs $100. And, I didn't expect a razor sharp image from my $380 Sigma 18-125. But, with my 2 L-glass lenses costing over $2,100, I /do/ expect sharpness, and I get it. But these things are huge and heavy, so again, there's always tradeoffs in life. I generally shoot at the medium 4MP size, but do go to the full 8MP fairly often. Since I print almost zero beyond 4x6, I resize down to no more that 1600 by xxx (aspect ratio) and be very conservative with my JPEG compressions. > With practice now I can get pretty sharp with the Canon EF > 70-300mm F4-5.6 with a Quantaray 2x teleconvertor, but [quoted text clipped - 4 lines] > gives. I am using a tripod, remote shutter switch, and > mirror lock-up, but still I am sure I can do better. I know why you use a converter, but I've never seen one in 40 years that didn't do a 600 grit sandpaper on my images. Another of those pesty compromise/tradeoffs. Since I generaly shoot at 4MP, I can get an effective 4X "digital" zoom at the max telephoto I have by going to 8, and cropping a 4MP out of the middle. > The eventual solution might be to learn to live with only a > 300mm focal distance and crop somewhat for smaller prints. > Even cropping out 4 of the 8 MP still gives a nice 4x6" > print while increasing the apparent focal distance a lot. Why? First, though, what are your main subjects? And, what PPI are you shooting for? With 4MP, which is 3456 x 2304, that's good for up to 17" x 12" at 200 PPI, which is overkill to the tune of having 3 nukes for every one the Soviets had. Or, the ages old boys showeroom measurements, after the minimum, the rest is just bragging. So, again I'll ask you. How about supplying some details of what you do and keep the discussion practical, instead of going into the tall weeds on perceived vs. real requirements? I'm not disputing anything you've said, I just can't give you a reliable opine without knowing more. e.g., I'm assuming you might like to shoot car races or other sports from a long distance, hence the need/desire for long lenses, and may also be interested in the real-world burst rate of the camera, taking into account AF lag, shutter lag, and time it takes to write both RAW and JPG to your CF. That don't mean squat to me, all my cars are sitting still. SignatureATM, aka Jerry > Why? First, though, what are your main subjects? And, what PPI > are you shooting for? With 4MP, which is 3456 x 2304, that's > good for up to 17" x 12" at 200 PPI, which is overkill to the > tune of having 3 nukes for every one the Soviets had. Or, the > ages old boys showeroom measurements, after the minimum, the > rest is just bragging. 3546x2304 is actually close to 8MP. I have read that 300-360ppi is appropriate for optimal prints. However it is certainly viewing distance dependant and the quality of the photolab making the prints probably affects it also. Upsampling during RAW conversion in Adobe Camera Raw works quite well also if more MP are needed. That said I have seen good 4x6's with even 2MP. The difference going to 8MP for 4x6's is only small but it is visible if you really scrutinize it. > So, again I'll ask you. How about supplying some details of > what you do and keep the discussion practical, instead of > going into the tall weeds on perceived vs. real requirements? > I'm not disputing anything you've said, I just can't give you > a reliable opine without knowing more. Sure. I don't have externally applied requirements. I simply enjoy the process of taking a picture and editing it and coming up with an image that has beauty (at least to me). I am not a professional photographer and no one pays me for my pictures. They are for my own enjoyment of trying to create an artistic or impressive image. I often like to take pictures of wildlife and for this a telephoto is quite useful when I want the subject to appear close-up. Sometimes even a landscape picture will look good in a long focal length, like a distant mountain that now fills the frame instead of having to drive an hour to get closer to it. Photography is just a hobby and creative outlet for me that I enjoy. Sometimes I take the picture to see details in something a ways away that I cannot see well with the naked eye. By taking a picture at 300mm or so and then blowing it up on a 20" monitor pixel per pixel, a great amount of detail can be seen that I may have been unaware of. Maybe there is a crop in there that would make an artistic picture. Creating panoramas by tiling images is quite fun and can give enormous depth of field, or incredible detail. These can be great fun to create, but usually I use a shorter lens for this, like the EF 50mm F/1.8 II. I noticed that quite a few of my pictures were at the extremes of focal length on my lenses, 70mm or 300mm on the 70-300, 18 or 55mm on the 18-55mm lens. This lead me to think that maybe a longer lens would be useful. However I didn't want to put a bunch of money into it just to get a bit more reach. I would rather put the money toward a future purchase of a EF-S 10-22mm and maybe the EF-S 17-85mm IS also to replace the 18-55mm. I am really happy with the EF 70-300mm IS. Image stabilization is really fantastic, and I would like it for the 17-85 end as well. So I decided to try a couple of inexpensive methods of reaching 500mm. If they worked out, then it might be good for taking pictures of small animals, or distant landscapes, both of which would be fun. Possibly some astrophotography would be possible with lenses over 500mm. I would like to take a few pictures of Jupiter and the Galilean moons etc. I know everyone has already photographed these things and I can download nice pictures from NASA, but there is the challenge and fun of making my own and developing the skills and artistic talent. It may be that I really don't need over 300mm, and I didnt want to shell out big bucks for a very long lens before seeing if long focal lengths are useful or pleasing to me. Clearly there are problems with going really long. Keeping the camera still is difficult with no IS. Tripods become a must. Depth of field gets really shallow. Trying to take a nice close-up of that duck or goose way out in the middle of the lake, may not be reasonable with a 500mm lens anway. I had been considering the Sigma 50-500mm lens as an option. It can be used with Sigma TC's as well, but after replacing my Sigma 70-300 DG lens with the Canon 70-300IS, I now see that IS is a must for hand-held photos. My pictures have improved and the percentage that turn out is higher. I can get away with lower shutter speeds which can mean less noise, or greater DOF, or lower light. So many more possibilities. So a 500mm lens with no IS may be only useful in very bright light or where tripods are convenient. Shutter speeds must be less than 1/1000s for sure to be hand-held. I tend to shake the camera sometimes if I use much less than 1/2F speeds without IS. There is a certain amount of diffraction or dispersion in air over very long distances especially from pollution that limits the contrast and sharpness of distant things anyway. I was hoping I could take good pictures of distant things without having to get close. I am learning this type of photography is not reasonable and that really sharp detailed images aren't possible over a few miles in this air. So all of that lead to manual focus solutions to try long focal lengths without a large outlay. It turns out that manual focus is quite difficult on a Rebel XT, especially for slow lenses. I was wondering if there was a technique or product to make manual focus work well. Possibly an eyepiece magnifier or something. Replacing the focussing screen seems to have trade-offs that aren't really acceptable at this point. http://photonotes.org/reviews/viewfinder-screen/ has some notes on this. I don't want to lose the autofocus indicator points to get a split circle and microprism collar that I would only use once in a while. It appears that these focussing aids don't work well with slow lenses anyway. Thanks for your comments and help. My feeling is that really accurate manual focus on long focal lengths may not be a strength for this camera. I see that the very expensive 1 series has the option of replaceable focusing screens so at the very high end, it can be done. I am not going to spend that kind of cash on a hobby endeavor. I would rather pay down my mortgage. The Rebel XT and a few lenses and filters are enough for almost everything that I want to do. The very long focal lengths were just an experiment that I wanted other more experienced opinions on how to make work. Today default commented courteously on the subject at hand > 3546x2304 is actually close to 8MP. I have read that > 300-360ppi is appropriate for optimal prints. However it [quoted text clipped - 5 lines] > for 4x6's is only small but it is visible if you really > scrutinize it. It is the 8MP setting, I mispoke. The 4MP setting I usually use is 24956 x 1664, normally more than adequate for my needs. >> So, again I'll ask you. How about supplying some details >> of what you do and keep the discussion practical, instead [quoted text clipped - 15 lines] > to it. Photography is just a hobby and creative outlet for > me that I enjoy. I wish I had creative talent but I don't, so I long ago changed to "documentary" photography where technical accuracy and just capturing a picture at all are more prized. I didn't think of wildlife, but I know a doctor who still uses a top-of-the-line Leica and spends upwards of $250 per custom 16x20. You just can't approach an animal so the longer the lens, within weight, size, price, sharpness and camera shake constraints, the better. > Sometimes I take the picture to see details in something a > ways away that I cannot see well with the naked eye. By > taking a picture at 300mm or so and then blowing it up on a > 20" monitor pixel per pixel, a great amount of detail can > be seen that I may have been unaware of. Maybe there is a > crop in there that would make an artistic picture. This is an example of when I put on my Sigma 18-125 (29-200mm equiv) and go to 8MP. Since my finished size will be no more than 1400x1050 (cropping to 4:3), I can an very large effective "digital zoom". > Creating panoramas by tiling images is quite fun and can > give enormous depth of field, or incredible detail. These > can be great fun to create, but usually I use a shorter > lens for this, like the EF 50mm F/1.8 II. I know how to do it, but there aren't many opportunities for a pano of cars at a show! <grin> > I noticed that quite a few of my pictures were at the > extremes of focal length on my lenses, 70mm or 300mm on the [quoted text clipped - 6 lines] > with the EF 70-300mm IS. Image stabilization is really > fantastic, and I would like it for the 17-85 end as well. I also like the foreshorted effect of mild-to-wild teles. In fact, I'll shoot my cars in the 85mm, sometimes 105mm range if I can because I so dislike the large foreground/receding background of a car shot low with a wide-angle. > So I decided to try a couple of inexpensive methods of > reaching 500mm. If they worked out, then it might be good [quoted text clipped - 6 lines] > from NASA, but there is the challenge and fun of making my > own and developing the skills and artistic talent. Can you still buy a folded mirror lens for a DSLR? I never needed one, but in my film days, the crowd that needed 500- 1000mm bought mirrors because they were much smaller, much lighter, and much cheaper. People used tele adapters then, too, and simply suffered with moderate-to-severe image degradation. But, again, it is what your expectation of quality is that matters, not dpreview's idea or mine. > It may be that I really don't need over 300mm, and I didnt > want to shell out big bucks for a very long lens before [quoted text clipped - 16 lines] > sure to be hand-held. I tend to shake the camera sometimes > if I use much less than 1/2F speeds without IS. Thanks for sharing that. Please keep in mind what I talked about before, life in general, and digital in particular, is one big set of compromizes. Go long in the best way that fits your pistol, but if you want to retain your sanity and your checkbook balance, shift some away from the theoretical and more to the practical. And, you already know how to do that. I would like IS as well, but it isn't available for the lenses I chose. But, I don't shoot long and I am trying to learn to tripod shoot still cars in available light, so IS in either the camera or lens isn't a necessity. > There is a certain amount of diffraction or dispersion in > air over very long distances especially from pollution that [quoted text clipped - 4 lines] > detailed images aren't possible over a few miles in this > air. Yes, pparticularly in early morning, with the mist and fog, and in the afternoon sun, with the thermals. UV also comes into play, so I assume you use both a UV and a polarizer. If not, try them, you'll like what you see very much. > So all of that lead to manual focus solutions to try long > focal lengths without a large outlay. It turns out that [quoted text clipped - 10 lines] > that these focussing aids don't work well with slow lenses > anyway. Now that I know what you do, why do you focus at all? At those distances, regardless of focal length, aren't you at infinity nearly all the time, or are you talking about shooting an animal from a couple hundred yards where accurate focus is a requirement and you want to creat a dramatic effect by blurring the background with a large aperture? > Thanks for your comments and help. My feeling is that > really accurate manual focus on long focal lengths may not [quoted text clipped - 7 lines] > experiment that I wanted other more experienced opinions on > how to make work. You're most welome. I respect what you're trying to do and hope you respect my completely different way to approach the task at hand. As to the camera, again, life is a compromise. If you had the bucks, I would've recommended the 20D. If you had even deeper pockets, I would recommend the new 16MP 5D. But, you don't, so you compromize with a decent lens and a TA. Been great talkin' to ya! SignatureATM, aka Jerry >Can you still buy a folded mirror lens for a DSLR? If they work on SLRs, they work on DSLRs with the same mounts. Most of the third-party lens companies offer 500 or 600mm mirror lenses; usually they are f/8. >I never >needed one, but in my film days, the crowd that needed 500- [quoted text clipped - 3 lines] >degradation. But, again, it is what your expectation of >quality is that matters, not dpreview's idea or mine. It also depends on how you look at the images. If all you'll ever see is a 6x4" print, or a small JPEG, then the "degradation" of budget telephotos, or any soft lens coupled with a TC is not going to be as apparent as it would be with a 36x24" large print, or cropped at 100% on the monitor. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< Today commented courteously on the subject at hand >>Can you still buy a folded mirror lens for a DSLR? > > If they work on SLRs, they work on DSLRs with the same > mounts. Most of the third-party lens companies offer 500 > or 600mm mirror lenses; usually they are f/8. I haven't followed this stuff for 40 years, so my question was pure ignorance, but it is harmless to me. >>I never >>needed one, but in my film days, the crowd that needed 500- [quoted text clipped - 10 lines] > would be with a 36x24" large print, or cropped at 100% on > the monitor. You know, JPS, sooner or later, usually sooner, a discussion like this will eventually get around to print sizes. I'm very much a contrarian on this, as I've long gotten very acceptable results on very large ink jet prints as low as 70 PPI. I just make sure nobody viewing it can get closer than 4-5 feet. But, if we can at all agree that 200 PPI is the threshold for "good" quality, here's the numbers I use: 4x6 = 1200x800 8x10 (on 8.5x11 paper) = 2000x800 11x14=2800x2200 16x20=4000x3200 Now, I wouldn't spend $250 on a custom print at less than this, but at the size I normally save to, 1280x960 or 1400x1050, I can still get to 8x10 if I view a little father away to live with only 140 PPI. And, "good" is like beauty, in the eyes of the beholder. Subject type, lighting, exposure, a whole raft of things experienced photographers know about, can all require more, or allow you to get by with less. SignatureATM, aka Jerry > My suspicion is that I don't have the > eyepiece diopter quite perfectly adjusted and am misfocussing, or that the > focus screen is not perfectly matched in distance as the image sensor. There are aftermarket focus screens for the Rebel XT with split prism and and microprisms. They may help you judge the point of focus. Be sure to research drawbacks, though. -Wolfgang |
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