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Photo Forum / Digital Photography / DSLR Cameras / August 2005DSLR with live-Histogram
Hi... Since its not possible to get a full live-preview, how can i get the metering of a picture right? When adjusting apperture and shutter on my dimage 7i I can watch the live histogram, and move it wher i want it to be. Is this possible with any DSLR? I'm afraid its not possible, since the large sensor is behind the mirror, but how is A and S calculated when im in Auto-Mode anyway? Thomas On a P&S, the sensor is always in the light path, so realtime image on the LCD is possible. An SLR sticks the reflex mirror in the path of the light, AND the real shutter is closed, so the sensor sees nothing until you fire the shutter. Therefore DSLR does not permit realtime viewing and histogram. You 'pay a price' for seeing exactly what the lens sees, in terms of the reflex mirror and shutter blinding the sensor until time of exposure. >On a P&S, the sensor is always in the light path, so realtime image on >the LCD is possible. An SLR sticks the reflex mirror in the path of [quoted text clipped - 3 lines] >lens sees, in terms of the reflex mirror and shutter blinding the >sensor until time of exposure. Actually a Pellicle Mirror DSLR could allow such real time viewing.. Canon made several film cameras with such a system. http://www.mir.com.my/rb/photography/hardwares/classics/eos/eoscamera/EOS-RT/ The RT in the EOS-RT stands for "Real Time". ******************************************************** "A nice man is a man of nasty ideas." _Introductions to History of the Reformation_ Jonathan Swift 1667-1745 >Actually a Pellicle Mirror DSLR could allow such real time viewing.. >Canon made several film cameras with such a system. Yes, I know. Canon tried the pellicle on a couple of different cameras. The 'split' light path robbed the film of light and also robbed the finder of brightness, and the pellicle also suffered the issue of dust on the pellicle in the light path to the film. I wasn't trying to write a comprehensive article on behind-the-lens, as some cameras also used mirrors with partial silvering in one small area (a take-off on the pellicle concept) to provide realtime metering. --wilt --Wilt > >Actually a Pellicle Mirror DSLR could allow such real time viewing.. > >Canon made several film cameras with such a system. [quoted text clipped - 3 lines] > robbed the finder of brightness, and the pellicle also suffered the > issue of dust on the pellicle in the light path to the film. 'tried'? All of the current DSLRs name a semitransparent mirror at 60:40. From that I read that only 60 % of light are given to the viewfinder, while 40 % are used what for? Auto-Focus? TTL? Why not live histogram or live preview? - Martin >> >Actually a Pellicle Mirror DSLR could allow such real time viewing.. >> >Canon made several film cameras with such a system. [quoted text clipped - 10 lines] >while 40 % are used what for? Auto-Focus? TTL? Why not live histogram or >live preview? You would have to open the shutter over the sensor. ******************************************************** "A nice man is a man of nasty ideas." _Introductions to History of the Reformation_ Jonathan Swift 1667-1745 On Tue, 16 Aug 2005 11:56:46 GMT, John A Stovall wrote: > >> >Actually a Pellicle Mirror DSLR could allow such real time viewing.. > >> >Canon made several film cameras with such a system. [quoted text clipped - 12 lines] > > You would have to open the shutter over the sensor. That's the reason why you actually can't do it. It does not explain why there is a semitransparent mirror and why you can't use this as desired. Apart from that, I'd be happy enough to accept both mirror lockup or slighty more image noise whenever I ask for histogram or monitor explicitly - it it's a noise topic at all. - Martin >That's the reason why you actually can't do it. It does not explain why >there is a semitransparent mirror and why you can't use this as desired. I have never seen details of the internal design of modern SLRs like they used to publish in the early days of TTL metering. You used to be able to read, in the popular press, about how a particular model of camera accomplished its metering. I suspect, if it is true about a semitransparent mirror being present, that either: 1) a fully transparent mirror allows the evaluative metering to function where the metering is not in the pentaprism, but is in the body of the camera, or 2) a transparent mirror segment(s) permit metering samples to be taken, but the segments being read are incomplete samples that cannot be used for histogram display purposes, in the every pixel is factored into the histogram. --Wilt >>On a P&S, the sensor is always in the light path, so realtime image on >>the LCD is possible. An SLR sticks the reflex mirror in the path of [quoted text clipped - 10 lines] > > The RT in the EOS-RT stands for "Real Time". The sensors used in DSLRs, even the Canon 20Dn, still do not allow real-time image viewing so it has nothing to do with the mirror or shutter. Mark >>>On a P&S, the sensor is always in the light path, so realtime image on >>>the LCD is possible. An SLR sticks the reflex mirror in the path of [quoted text clipped - 16 lines] > > Mark It would be nice to have an option for the last shot's hostogram pop up as an overlay in the viewfinder so you did not have to take the camera away from they eye to check. > It would be nice to have an option for the last shot's hostogram pop up as > an overlay in the viewfinder so you did not have to take the camera away > from they eye to check. If you learn how to create images properly, you don't need no steenking histogram. >> It would be nice to have an option for the last shot's hostogram pop up as >> an overlay in the viewfinder so you did not have to take the camera away >> from they eye to check. > >If you learn how to create images properly, you don't need no steenking >histogram. I wonder how many people who say what you just said really mean "I routinely under-expose to avoid clipping, and get highly quantized shadows as a result". Only if you nail the exposure with the highlights just short of clipping the RAW data every time do you have bragging rights over the people who want more useful histograms, IMO.  Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >> If you learn how to create images properly, you don't need no steenking >> histogram. [quoted text clipped - 4 lines] > just short of clipping the RAW data every time do you have bragging > rights over the people who want more useful histograms, IMO. It's just misplaced bravado. Sure, with no image review and histogram I can get just as good an exposure as I did with film, back in the day. With those things, I can get *better*. SignatureJeremy | jeremy@exit109.com "Jeremy Nixon" <jeremy@exit109.com> wrote in message > It's just misplaced bravado. Sure, with no image review and histogram I > can get just as good an exposure as I did with film, back in the day. > With those things, I can get *better*. There is no "better" exposure. There is only an exposure that interprets the scene in such a way as to make the statement the artist wishes to make. ;) SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >"Jeremy Nixon" <jeremy@exit109.com> wrote in message > [quoted text clipped - 5 lines] >the scene in such a way as to make the statement the artist wishes to make. >;) I seriously doubt that the artist has any idea exactly how their image is going to posterize; you get maximum control when you expose digital as high as possible without clipping desired highlights, and then "ruin" it artistically in post-processing. As far as getting better saturation by under-exposing is concerned, that is total nonsense with digital, if you have access to the RAW data. Under-exposure only gets you the random color noise of posterization. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >> It would be nice to have an option for the last shot's hostogram pop up >> as [quoted text clipped - 3 lines] > If you learn how to create images properly, you don't need no steenking > histogram. OK well you go back to film then and mutter to youreself about damm progress.... > > If you learn how to create images properly, you don't need no steenking > > histogram. > > OK well you go back to film then and mutter to youreself about damm > progress.... I don't see myself going back to film, but as one who has done photography for almost 40 years with no histogram, I see no reason for one now. If one learns the principles of photography, there is no need for histograms. >> > If you learn how to create images properly, you don't need no steenking >> > histogram. [quoted text clipped - 6 lines] > one now. If one learns the principles of photography, there is no need > for histograms. Yep, I worked with film and no histogram for 25 years. I tended to prefer a manual camera with a tight metering, close to what would be called spot today. I sometimes used seperate incident light or 1 degree spot meters if I was being fussy. I could use those methods now but the histogram is better. I do see the advantage of histograms - but you can use it or not. What I am saying is an overlay histogram would improve the usability when you do want to use them. A CF could be defined to turn the feature off if one found it distracting. I use the histogram on every shot if there is time, it allows confirmation of metering. The only problem is operating fast you can't take your eye away to use this advantage. The overlay would solve that. > It would be nice to have an option for the last shot's hostogram pop up as > an overlay in the viewfinder so you did not have to take the camera away > from they eye to check. And how would they do that function? I don't see how a SLR viewfinder would do an overlay, are you suggesting they replace the reflex housing with a EVF? > > It would be nice to have an option for the last shot's hostogram pop up as > > an overlay in the viewfinder so you did not have to take the camera away [quoted text clipped - 3 lines] > do an overlay, are you suggesting they replace the reflex housing with a > EVF? The information could be projected on the focusing screen like a HUD. But don't take this as an endorsement for the idea. Real men don't need histograms. ;) Please be careful even saying EVF and SLR viewfinder in the same sentence - I'm afraid someone at the big 2 companies might read that and think it's a /good/ idea and then photography will be ruined forever. :o SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >> It would be nice to have an option for the last shot's hostogram pop up >> as an overlay in the viewfinder so you did not have to take the camera [quoted text clipped - 3 lines] > would do an overlay, are you suggesting they replace the reflex housing > with a EVF? Well I did say nice, but not as a EVF. I can't say I have thought of it otherwise I would be talking to patent agent rather than the PD. I guess I was thinking of something like head-up display technology. I guess the same as they dp with the AF spots. Little LED display or backlit LCD display projecting into the view. >On a P&S, the sensor is always in the light path, so realtime image on >the LCD is possible. An SLR sticks the reflex mirror in the path of [quoted text clipped - 3 lines] >lens sees, in terms of the reflex mirror and shutter blinding the >sensor until time of exposure. Blinding and *protecting* the sensor. Without that, a chance positioning of the camera -- perhaps when you set it down outdoors, can focus an image of the sun directly onto the focal plane, and the larger lenses in DSLRs can gather and focus more energy onto the focal plane, thus increasing the chances of damage. (Old film SLRs sometimes used rubberized cloth focal plane shutters, and these could also be damaged by focusing the sun onto the shutter -- resulting in a pinhole in the shutter curtain, which will spoil all subsequent film exposures. Modern focal plane shutters are typically very thin titanium metal, which can easily stand the temperatures of such an image -- but you still risk damaging the focusing and exposure sensors in the focusing screen. (And the focusing and exposure sensors in the focusing screen are how the camera determines its exposure settings, to deal with the second question in your original post. (Perhaps some other followup dealt with that, but this one did not, so I decided to toss it in now. Good Luck, DoN. SignatureEmail: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- >>On a P&S, the sensor is always in the light path, so realtime image on >>the LCD is possible. An SLR sticks the reflex mirror in the path of [quoted text clipped - 9 lines] > lenses in DSLRs can gather and focus more energy onto the focal plane, > thus increasing the chances of damage. And it protects the sensor by focusing the sun into the operators eyes. Might make sense with an D1sII, where a new eye is cheaper than a new camera ;-) >>>On a P&S, the sensor is always in the light path, so realtime image on >>>the LCD is possible. An SLR sticks the reflex mirror in the path of [quoted text clipped - 13 lines] >Might make sense with an D1sII, where a new eye is cheaper than a new >camera ;-) Unlike the camera, the human eye is connected to an automatic positioning system which will remove the sun image *very* quickly. :-) I have yet to see a camera set up to reorient itself if threatened by the sun burning the sensor. Not to mention the automatic protective shutters with eyelashes available to the eye. :-) Enjoy, DoN. SignatureEmail: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- >>And it protects the sensor by focusing the sun into the operators eyes. >>Might make sense with an D1sII, where a new eye is cheaper than a new >>camera ;-) > > Unlike the camera, the human eye is connected to an automatic > positioning system which will remove the sun image *very* quickly. :-) Im not sure, that you will blink fast enough if you focus into the sun with a 300mm/2.8 with a FullFrame-Camera with bright EVF. On the other hand, its a rather stupdi thing to do anyway. > In article <ddsg4a$2si$1@svr12.m-online.net>, > [quoted text clipped - 6 lines] > Not to mention the automatic protective shutters with eyelashes > available to the eye. :-) My new test camera has a sensor next to the photosensors that detects sudden temperature shifts, such as caused by a beam of direct sunlight through the lens, and puts out a burst of electo magnetic force that'll snap the lens cap back on if it's within 18" of the special filter mount that produces the magnetic shock wave. Just keep you cell phone at a distance! And pens. SignatureJohn McWilliams > On a P&S, the sensor is always in the light path, so realtime image on > the LCD is possible. An SLR sticks the reflex mirror in the path of [quoted text clipped - 3 lines] > lens sees, in terms of the reflex mirror and shutter blinding the > sensor until time of exposure. That's not really the limitation. The consumer-level cameras all use very different sensors than the DSLR's. The tiny sensors have a special low-resolution preview mode to allow rapid update. The much larger DSLR sensors would consume far more power in such a mode, depleting battery charge and overheating the sensor. For example, the late lamented full-frame Kodak DSLR's had a long-exposure mode that was limited to 30 seconds for this reason. Signature-Stephen H. Westin Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors. <<but how is A and S calculated when im in Auto-Mode anyway? >> In most SLRs a small amount of light is diverted from the viewfinder light, and the aperture and speed are calculated by that, immediately prior to mirror going up and opening the shutter. In some designs (Olympus OM-4), the photosensor lies at the bottom of the camera body and points at the film, so it is able to monitor changes in light as the exposure is actually made -- off the film 'OTF'! > Since its not possible to get a full live-preview, how can i get the > metering of a picture right? Before the dSLR, there was the SLR. > Hi... Since its not possible to get a full live-preview, how can i > get the metering of a picture right? When adjusting apperture and [quoted text clipped - 4 lines] > the large sensor is behind the mirror, but how is A and S calculated > when im in Auto-Mode anyway? DSLR's meter as SLR's... in most cases today, the metering is done up in the pentaprism area. If your DSLR has a spot meter, then you can point it at your highlights and set for +1.5 to +2 (camera model dependant) and get a fairly full histogram on the highlight side. Or, in true chimpeze, take a test shot and adjust. Cheers, Alan 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. > Hi... > Since its not possible to get a full live-preview, how can i get the [quoted text clipped - 6 lines] > > Thomas Use the Force Thomas. :) Ok, I'm not really joking. For about the last two years I shot film only (excepting my compact digital). I remember being frustrated at first not being sure what exposures would work - my confidence was zero. After a while I got to where I could practically eye ball the exposure. The important thing is that in the previous year I had learned very little about exposure using my F717. Why? Because I didn't have to *think*. I could just move the camera around and spot meter areas until the histogram and LCD sorta matched what I thought I wanted to accomplish. Now I'm shooting with a 20D (about 1 week now) and I'm grateful for the mental workout I got from shooting film. The greatest photographers of the 20th century didn't have histograms to work from. ;) SignatureMark Photos, Ideas & Opinions http://www.marklauter.com > Hi... > Since its not possible to get a full live-preview, how can i get the [quoted text clipped - 8 lines] > > Thomas You can view the histogram immediately after taking the photo. Wow, I wonder how I did it with a film SLR - no image or histogram review at all! Mark > You can view the histogram immediately after taking the photo. Wow, I > wonder how I did it with a film SLR - no image or histogram review at all! I never look at them on my 10D. I've done film long enough, I know what it's going to look like before I press the button. Thomas =?ISO-8859-15?Q?M=FCller?= <spam@elfstone.de> wrote in news:ddr837$vc1$1@svr12.m-online.net: > Since its not possible to get a full live-preview, how can i get the > metering of a picture right? Is there a reason why you cannot take the photo, check the histogram, adjust the metering and then take another photo? This can't be done with a film SLR, but we are not talking about a film SLR, digital does have an advantage in this respect. SignatureMark Heyes (New Zealand) See my pics at www.gigatech.co.nz (last updated 16-August-05) "There are 10 types of people, those that understand binary and those that don't" > Thomas =?ISO-8859-15?Q?M=FCller?= <spam@elfstone.de> wrote in > news:ddr837$vc1$1@svr12.m-online.net: [quoted text clipped - 7 lines] > film SLR, but we are not talking about a film SLR, digital does have an > advantage in this respect. You mean like we used to do Polaroid tests ;) >> Thomas =?ISO-8859-15?Q?M=FCller?= <spam@elfstone.de> wrote in >> news:ddr837$vc1$1@svr12.m-online.net: [quoted text clipped - 9 lines] >> > You mean like we used to do Polaroid tests ;) Yeah, similar but better. Better as in faster and more accurate. With a D-SLR you get your "Polaroid test" with the same camera and same film as your final shot and you can see the image within a second or two of taking the shot. SignatureMark Heyes (New Zealand) See my pics at www.gigatech.co.nz (last updated 16-August-05) "There are 10 types of people, those that understand binary and those that don't" >Thomas =?ISO-8859-15?Q?M=FCller?= <spam@elfstone.de> wrote in >news:ddr837$vc1$1@svr12.m-online.net: [quoted text clipped - 6 lines] >film SLR, but we are not talking about a film SLR, digital does have an >advantage in this respect. It might be too late? Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >>> Since its not possible to get a full live-preview, how can i get the >>> metering of a picture right? [quoted text clipped - 5 lines] > > It might be too late? Zen Master Nansen was strolling beside his favourite pond on the way to the monastery. Suddenly, a Twelve Spotted Skimmer (Libellula pulchella) alighted on a nearby blade of grass. Without thinking, he pulled out his Canon 1DMkII equipped with EF 300/4 + 2x teleconverter, and rattled off 4 frames before the dragonfly flew off. Nansen checked the histogram, and saw that the image was not only over exposed, but out of focus. "sh.t happens", said Nansen, and at that instant he was enlightened. >>It might be too late? > [quoted text clipped - 6 lines] > out of focus. "sh.t happens", said Nansen, and at that instant he was > enlightened. Yes, Grasshopper, yes. But tell me, please, how did he know from the histogram that his focus was borked? SignatureJohn McWilliams > Yes, Grasshopper, yes. But tell me, please, how did he know from the > histogram that his focus was borked? The vertical bars on the histogram were fuzzy. ;) SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >> Yes, Grasshopper, yes. But tell me, please, how did he know from the >> histogram that his focus was borked? > >The vertical bars on the histogram were fuzzy. ;) Which reminds me; I have to get sturdier stands for my lights. The current ones wobble and blur the images. :) Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > Yes, Grasshopper, yes. But tell me, please, how did he know from the > histogram that his focus was borked? By asking such questions, you only entangle yourself further in the foul nexus of dualism. When you meet the Buddha, you must kill the Buddha. >>Yes, Grasshopper, yes. But tell me, please, how did he know from the >>histogram that his focus was borked? > > By asking such questions, you only entangle yourself further in the > foul nexus of dualism. When you meet the Buddha, you must kill the > Buddha. Forgive my impertinance, O Buddha! Signaturejpmcw |
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