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Photo Forum / Digital Photography / DSLR Cameras / March 2006Canon EOS350D/Rebel XT - Depth of field problems
My wife has an Olympus digital 'instamatic' type of camera (3 megapixels) that takes excellent quality photographs. She uses it on the fully automatic mode with no problems whatsoever. We did though both want a digital SLR and the extra flexibility that it provides (ie being able to see what you were looking at through the viewfinder plus lens interchangeability) so we bought a Canon EOS 350D/Rebel XT. The problem we have is with the fully automatic mode and the depth of field - it really is very poor. For example, she enjoys taking indoor photographs of our dogs - with the old Olympus most of the subject remains in focus, but with the 350D we can perhaps get the nose of the dog in focus but the rest is slightly out of focus. The lens we are using is the Canon EF 35-80mm zoom - I used to use it on my old 35mm camera with no depth of field problems whatsoever. No doubt this could be improved after messing around with the aperture settings, focus points, etc but as far as we're concerned if the cheaper, older 'instamatic' digital camera can use its' fully automatic mode to get everything in focus then so should this modern and more expensive camera. But it doesn't. Where are we going wrong? Thanks matt trolls lamely: > The lens we are using is the Canon EF 35-80mm zoom - I used to use it > on my old 35mm camera with no depth of field problems whatsoever. The depth of field is a function of the lens not the imaging substrate. > No doubt this could be improved after messing around with the aperture > settings, focus points, etc but as far as we're concerned if the > cheaper, older 'instamatic' digital camera can use its' fully > automatic mode to get everything in focus then so should this modern > and more expensive camera. But it doesn't. You know, I was thinking the other day, "This god damned Canon EOS-1D MkII of mine is completely useless! The pinnacle of modern imaging technology, albeit last year, and it has had absolutely nothing to say about the P = NP problem. One would think such a contraption should have at least advanced the state of the art regarding this issue. But it didn't! I think those bastards at Canon should pay for their technological malfeasance!" > Where are we going wrong? You are trolling USENET. Instead you should: a) RTFM. b) Buy a book. c) Experiment. d) Use your head. > matt trolls lamely: > > > The lens we are using is the Canon EF 35-80mm zoom - I used to use it > > on my old 35mm camera with no depth of field problems whatsoever. > > The depth of field is a function of the lens not the imaging substrate. <snip> Actually, DoF is a function of the object-size/image-size ratio, and the f-stop employed. For a given f-stop, the larger the image size relative to the object size, the shallower is the dof. The sensor in most compacts is about 7mm x 9mm, or even less, while the sensor in a 350D is 15mm x 22mm, so the image size of a dog filling both sensors will be much bigger in the 350D, hence the dof will be shallower. A full-frame 35mm has less dof still, and a 5x4 will have even less than that. Colin D. >No doubt this could be improved after messing around with the aperture >settings, focus points, etc but as far as we're concerned if the [quoted text clipped - 3 lines] > >Where are we going wrong? Your expectations. Due to the very small actual focal lengths of P&S cameras the DOF is extremely large, even wide open. Put your XT in aperture priority mode, set f/8 or better and take your shots. Also look at the AF setting. Default might be closest subject. -- Ed Ruf Lifetime AMA# 344007 (Usenet2@EdwardG.Ruf.com) http://EdwardGRuf.com > >No doubt this could be improved after messing around with the aperture > >settings, focus points, etc but as far as we're concerned if the [quoted text clipped - 8 lines] > priority mode, set f/8 or better and take your shots. Also look at the AF > setting. Default might be closest subject. I'll 2nd what Ed said. Think of the 350D as being like a Formula 1 car - it's a lot harder to drive than you're average 2.4 litre automatic, but once you get the hang of it you get a phenominal increase in performance. As Ed suggested, but the camera in Av mode - select F8 - F11 - and see how you go. If it wants a relatively slow shutter speed (say anything less than 1/60th) then consider upping the ISO to 200 or 400 (or using a tripod) (you could also use the built-in flash, although you'll get much better results with an external flash unit like the EX-580). Let us know how you get on. Cheers, Colin >My wife has an Olympus digital 'instamatic' type of camera (3 >megapixels) that takes excellent quality photographs. She uses it on [quoted text clipped - 23 lines] > >Thanks Try 'A-DEP'  SignatureIan G8ILZ Today matt commented courteously on the subject at hand > My wife has an Olympus digital 'instamatic' type of camera > (3 megapixels) that takes excellent quality photographs. [quoted text clipped - 25 lines] > > Where are we going wrong? Maybe you're suffering from the same thing I did when I got my Rebel right after Christmas. By default, the Rebel uses from one to eight of eight possible AF sampling points. So, even though I was using AF lock, it was picking up a different part of the subject than I intended. I turned the auto sampling mode off in favor of only one AF point in the center of the screen, which has helped immensely. One other "trick" you might try is to shoot at the max 8 MP (if you aren't already), and use as wide angle as you have, then crop the dogs et al out of the middle. As you obviously know, smaller focal length means more DOF. Then, there's flash. If you're shooting flash in either Auto or Programmed Auto, the camera locks the lens wide open and adjusts the flash to do the exposure. As expected, this plays havoc with DOF. Two solutions, re-remember the 1/3-2/3 rule for AF lock and switch to Aperture Priority and use a smaller aperture. SignatureATM, aka Jerry "Whether You Think You CAN Or CAN'T, You're Right." – Henry Ford > Then, there's flash. If you're shooting flash in either Auto > or Programmed Auto, the camera locks the lens wide open and > adjusts the flash to do the exposure. As expected, this plays > havoc with DOF. Two solutions, re-remember the 1/3-2/3 rule > for AF lock and switch to Aperture Priority and use a smaller > aperture. Hmm... trying to learn here: could you explain more about this "1/3- 2/3 rule for AF lock"? I've been reading up and learning things for some time now, but this sounds new to me. Thanks a lot! Wald Today wald commented courteously on the subject at hand >> Then, there's flash. If you're shooting flash in either >> Auto or Programmed Auto, the camera locks the lens wide >> open and adjusts the flash to do the exposure. As >> expected, this plays havoc with DOF. Two solutions, >> re-remember the 1/3-2/3 rule for AF lock and switch to >> Aperture Priority and use a smaller aperture. > Hmm... trying to learn here: could you explain more about > this "1/3- 2/3 rule for AF lock"? I've been reading up and > learning things for some time now, but this sounds new to > me. Old photographer's general rule: using whatever size COF (Circles Of Confusion) you want to use to define DOF (Depth Of Field), about 1/3 of the primary subject will look in-focus in front of the point focused and about 2/3 will look in-focus behind the point focused. So, when you're shooting a subject that's at an angle, a car for me or a dog for you, focus about 1/3 from front-to-back and hope for the best possible DOF at any given aperture and any given focal length lens. DOF is independent of lens type but is dependent on the shorter focal lenght lenses used on small frame digitals. That's a positive side effect that gives non-full frame digitals that ordinary people can afford much more DOF than they'd get with an equivalent focal length lens on a 35mm film camera. Incidently, from a purely mathematical point of view, there really is no such thing as DOF. Only one spot in the scene is really in-focus. It is an illusion, like a lot of concepts in photography are. COF was developed by the very early photographers when they noticed that point sources of detail in a subject looked like small circles in areas of slight to moderate blurriness. They developed guidelines for how large these "circles of confusion" - i.e. amount out-of-focus - should be for the illusion of a sharp image, then created DOF charts to guide them. This was eventually standardized across the industry and extensive DOF tables printed showing approximate DOF for various focal length lenses on various size cameras at various distances focused. Google for "depth of field" and "circles of confusion" and you can get the technical facts that are buried in my old Nikon Technical Manual gathering dust in my basement that I'm too lazy to go get to be more precise about this. Being that I am a pragmatist and not a theorotician, I can't help you with the math and technical specs but if you have real-world questions, I'll try to lend my experience - such that it is - to help you. SignatureATM, aka Jerry "Whether You Think You CAN Or CAN'T, You're Right." – Henry Ford > Today wald commented courteously on the subject at hand > [quoted text clipped - 9 lines] > front of the point focused and about 2/3 will look in-focus > behind the point focused. <snip> Wow, thanks for taking the time to write that down! Gives some good pointers for further reading... the historical perspective is quite interesting. Thanks a lot, Wald Today wald commented courteously on the subject at hand >>> Hmm... trying to learn here: could you explain more about >>> this "1/3- 2/3 rule for AF lock"? [quoted text clipped - 10 lines] > some good pointers for further reading... the historical > perspective is quite interesting. Glad it was of help, Wald. Ask anytime. SignatureATM, aka Jerry "Whether You Think You CAN Or CAN'T, You're Right." – Henry Ford >Incidently, from a purely mathematical point of view, there >really is no such thing as DOF. Only one spot in the scene is >really in-focus. It is an illusion, like a lot of concepts in >photography are. What you are saying is true at wide apertures, but when you stop down enough that diffraction is very strong, then quite a bit of depth is at the maximum sharpness possible, even though it is less than the sharpness of less depth at a larger aperture. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >> Incidently, from a purely mathematical point of view, there >> really is no such thing as DOF. Only one spot in the scene is [quoted text clipped - 5 lines] > the maximum sharpness possible, even though it is less than the > sharpness of less depth at a larger aperture. The illusion becomes reality when the circles are small enough that whatever sensor medium is being used ends up resolving them as point details anyway. SignatureJeremy | jeremy@exit109.com Today Jeremy Nixon commented courteously on the subject at hand >>> Incidently, from a purely mathematical point of view, >>> there really is no such thing as DOF. Only one spot in [quoted text clipped - 10 lines] > enough that whatever sensor medium is being used ends up > resolving them as point details anyway. That's true, Jeremy, just like one can have an accurate focus/DOF combination as desired by "adjusting" the COF in traditional film photography. When COF is smaller than a lens can resolve fine detail, the film grain discern two distinct objects, or a digitals sensors can distinguish two objects very close together, the theoretical discussion becomes moot - what the camera "sees" is one object. Did you or any lurkers ever have the "oportunity" of driving Army trucks at night with "cat eye" lights in front and rear? The idea was /not/ for the driver to see but for on-coming trucks and following trucks to see /you/. Two sets of narrowly spaced vertical slits - the eyes of the cat - showed up as single lines if you were following at too far a distance and showed as 4 sets of lines if you were too close. Same basic principle as COF and sensor limitations you talk about above. SignatureATM, aka Jerry "Whether You Think You CAN Or CAN'T, You're Right." – Henry Ford Today commented courteously on the subject at hand >>Incidently, from a purely mathematical point of view, there >>really is no such thing as DOF. Only one spot in the scene [quoted text clipped - 6 lines] > even though it is less than the sharpness of less depth at > a larger aperture. What I say is true at /any/ aperture from a /mathematical/ standpoint, as I said in the snip above. Focus is focus is focus, easily "proven" with a simple magnifying glass setting a blade of grass on fire by concentrating the rays of the sun on it. There is really only one point of true focus. The concept of "more" or "less" goes to the definition of "depth of field" and varies not only by aperture but by the lens focal length as has been discussed elsewhere. Now, since we live in a real world and not in one populated by only mathematicians and theoretical physicists, you are correct, smaller apertures give not only the illusion of focus and sharpnesss, they provide real-world visible focus - along with defects due to the design of a particular lens. Another illusion and popular misconception is so-called "perspective distortion" such as tall buildings appearing to tip over backwards when shot from the ground with the camera tilted up at a high angle. "Perspective" it certainly is but "distortion" it is /not/. Our eyes "see" the "distortion" as well, which is mathematically correct as the parallel lines of the building recede to infinity, but the CPU in our head says "hey, it can't be tilted, so I'll 'see' it as straight rectilinear". Cameras have no such CPU. Neither can a camera correct the "distortion" of taking a "dramatic" photo of a large object from a low angle with a wide-angle lens where the front of the object looms large and the rear recedes in size very rapidly. This isn't "distortion" for the same reason - the eye sees it but the brain "corrects" for it. You elitists reading this? Jerry actually /does/ know much of the stuff you take great delight in making sport about. Nows the time - flame Jerry for not listening and not believing and the new one, calling Bart or somebody a liar. Rant on, elitists unite to squash the unworthy infidel. SignatureATM, aka Jerry "Whether You Think You CAN Or CAN'T, You're Right." – Henry Ford > JPS wrote: > > What you are saying is true at wide apertures, but when you [quoted text clipped - 11 lines] > of field" and varies not only by aperture but by the lens > focal length as has been discussed elsewhere. No. What you are saying would be true if geometrical optics was correct, ie if the wavelength of light was zero. However, it's not, and this results in diffraction effects. A point source is imaged by a circular aperture as an Airy function. see, for example, a nice and simple explanation here: http://hyperphysics.phy-astr.gsu.edu/Hbase/phyopt/cirapp2.html Things are not as clear-cut as you say. Today commented courteously on the subject at hand >> JPS wrote: >> > What you are saying is true at wide apertures, but when [quoted text clipped - 21 lines] > http://hyperphysics.phy-astr.gsu.edu/Hbase/phyopt/cirapp2.ht > ml Things are not as clear-cut as you say. another elitist response, i see. if you stick with the real world, dof is quite easy to understand: it gets larger with the bigger cof and smaller with smaller cof, it gets larger as the distance focused increases and vice versa, and it gets larger as the lens (any lens) focal length gets shorter and vice versa. all the rest is theoretical bullshit that normal people cannot measure outside a lab. non-elitists want to take pictures and want to know how to get the best composure/exposure, want to know the most reliable way(s) to get good af lock, want the most of the main subject to look in-focus, want to know how to improve dof for situations where no obvious solutions occurs to them, and they want to know what can be done to improve slightly blurry pictures. only elitists want to grovel down in the dirt about diffraction effects. lest you think i don't understand this, you're wrong. i do. but, i neither follow nor care about diffraction or max lines a lens can resolve or the best/worst sensor size/type as i cannot measure it when i am in the field taking pictures and i cannot do anything about it when buying a camera or lens other than to not buy one with bad qualities. so, i /still/ stand by my earlier pronouncement: buy good glass, learn to use your camera well, use aperture and shutter consistent with light available and the photographic effect you want to achieve and decide if there is or is not enough dof. if you want to play theorticican, you could load your pda with millions of lines of specs from all the lenses in the world, including their diffraction and resolutions characteristics, their barrel/pincushion distortion specs, chromatic aberration as focal lenght and aperture change, as well as dof tables compiled over the ages using standard and altered sizes for cof, then - in the heat of battle - consult your pda to find out how best to determine point-of-focus and best estimate of dof. or, you could just push the little button on your camera or lens that shows an approximation of dof, decide if that works, and move on with your life. when people like you take me on, you really never know exactly what my knowledge and experience is across a very broad spectrum of subjects, even a broad spectrum of subjects under the general heading of "photography" or the narrower one of "digital photography" when you decide i'm full of sh.t. as such, you "expert" legends-in-your-own-mind elitists are never quite sure if i am what i say i am - a pragmatist - or a bullshit artist or stupid or ignorant or just an ordinary a.shole. but, i do know what you are - fodder for the dust bin. enjoy talking to your buds in the exclusive elitist club. SignatureATM, aka Jerry "Whether You Think You CAN Or CAN'T, You're Right." – Henry Ford > another elitist response, i see. if you stick with the real > world, dof is quite easy to understand: it gets larger with Elitist? It's the truth. If you actually calculate the size of the image of the point (or, since you're a practical man, measure it), it gets roughly equal to the size of a pixel (on the sensor) around f/11 for something like 60mm focal length; obviously this depends on the colour of the light, the sensor size and resolution etc (the number may be slightly off, but the order of magnitude is correct). So beyond that, it affects real world resolution. > vice versa. all the rest is theoretical bullshit that normal > people cannot measure outside a lab. non-elitists want to take No, you can see this effect in images easily, especially with cameras with small sensors and lots of pixels (like the Nikon D200 or, even more, the D2X). This is also the reason (or at least part of it) that point and shoots have min apertures of around f8 or so (beyond that, diffraction effects would be very noticeable) > lest you think i don't understand this, you're wrong. i do. Well, your behaviour in several threads I've happened to see strongly suggests otherwise. That's not a problem in itself, of course. Nobody knows everything there is to know. > but, i neither follow nor care about diffraction or max lines > a lens can resolve or the best/worst sensor size/type as i The effect I talked about is present whenever light passes through a circular aperture (well through any aperture but a point becomes an airy function only if the aperture is circular). > when people like you take me on, you really never know exactly > what my knowledge and experience is across a very broad [quoted text clipped - 5 lines] > bullshit artist or stupid or ignorant or just an ordinary > a.shole. You seem to be fixated on the idea that "we" are out to get you. Nobody is, but if you react as if you were insulted whenever someone points out that something you said isn't true, I suspect people will begin to think of you as a troll. I personally am not "taking you on", all I did was point out that what you said is incomplete (plus another response in another thread where you clearly demonstrated you had no idea what you were talking about). I couldn't care less what your knowledge and experience is except inasmuch as it affects what you say in the relevant discussion, and, as far as I can see, your knowledge is not as deep as you imply. I also am far from an expert in optics, but the things I said are fairly simple and any physicist would know them (or be able to work them out quite easily). Insisting they're irrelevant doesn't change reality. > but, i do know what you are - fodder for the dust bin. enjoy > talking to your buds in the exclusive elitist club. To return the compliment, the opinion I have formed of you in the recent past is that you are a pompous idiot. Idiots I don't really mind, but pompous idiots I really dislike. Today commented courteously on the subject at hand >> another elitist response, i see. if you stick with the >> real world, dof is quite easy to understand: it gets >> larger with > > Elitist? because you want to flick fly sh.t off the back of flies, which normal photographers do not want to do. I won't comment on the rest of your babble as it simply supports my thesis - you're a legend-in-your-own-mind would-be "expert" who has no practical knowledge to share, but who just wants to pick fights with people for no reason. It's the truth. If you actually calculate the size > of the image of the point (or, since you're a practical > man, measure it), it gets roughly equal to the size of a [quoted text clipped - 64 lines] > To return the compliment, the opinion I have formed of you > in the recent past is that you are a pompous idiot. don't know much about English, huh? idiots cannot be pompous and pompous people are not idiots. I could use some choice words on you, in fact, I think I will: miscreant, stupid, ignorant, naive, lacking in judgment, and overall miscreant. Happy now, troll? Idiots > I don't really mind, but pompous idiots I really dislike. rant on, miscreant, you'll be talking to the air SignatureATM, aka Jerry "Whether You Think You CAN Or CAN'T, You're Right." – Henry Ford > One other "trick" you might try is to shoot at the max 8 MP > (if you aren't already), and use as wide angle as you have, > then crop the dogs et al out of the middle. As you obviously > know, smaller focal length means more DOF. I'm not sure this is correct Jerry. When you crop, that's the same effect as zooming in & the DOF is lost. Not trying to pick on you, lots of other helpful comments here... It is true that shooting at a wider zoom gives more DOF & more light, the OP's 35-80mm lens is 1.6x longer now so he doesn't have the option of going wider than normal. I think that may be the problem and a wider lens is the solution. Today Paul Furman commented courteously on the subject at hand >> One other "trick" you might try is to shoot at the max 8 >> MP (if you aren't already), and use as wide angle as you [quoted text clipped - 8 lines] > doesn't have the option of going wider than normal. I think > that may be the problem and a wider lens is the solution. My point, Paul, which is correct in theory, is to stand back which gives you more DOF due to longer distance focused and/or use a wider angle - read: smaller focal length lens - which gives you more inherent DOF. If the OP is already at minimum focal length, they can't go wider but they can stand farther back - sometimes. The "trick" of using more MP then cropping out of the middle is designed /not/ to do a digital zoom (see below for an example), but to give you pixels to work with in the first place. I have been very successful with this technique taking candids of my daughter's very exhuberant Chihuaua. Daisy seldom sits still except when begging for treats, she is always moving and at a pretty good clip. And, since my Rebel XT still takes /some/ time between pressing the shutter and taking an image, I have more time to compose a rapidly moving target and the higher DOF I achieve using my technique helps the AF function to give me a better chance at a reasonable focus. There just isn't time to compose and do a traditional AF lock, the dog is long gone. So, I'm hardly disputing you, and I do thank you for the respect you've shown to my past comments. I'm simply illustrating an alternative way to look at the DOF problem in a particular shooting situation. Buried in this thread, I think, the OP said they were having trouble with getting a dog in focus. Turns out that few of the things suggested were what actually solved the problem, but everyone - including me - learned something from reading what others had tried in the past, what had worked and what didn't. If you monitor what I say in the two main digital camera NGs, you know I am anti- the mass marketing hype about "more mega pixels equals better pictures" without taking the entire process into mind. In my case, I generally shoot at the middle 4 MP size as it is ample for my needs, since my finished image size is only /very/ seldom larger than 1600 x 1200. Back to digital zoom through cropping: When I simply cannot get closer and I'm at the limit of the particular zoom lens at max telephoto, I will go to 8 MP and crop out a 1600 x 1200 image from the middle. This is /not/ an ersatz "digital zoom" since I did /not/ crop then resize up. That would have been the case if I'd cropped from the 4 MP image and attempted to resize up, albeit mathematically correct resampling is better than pixel resize but will still degrade the image. So, if you have a decent lens, like my two Canon L-glass zooms, a good camera, and you make a good exposure, you can in effect create a longer focal lenght lens through using more than the usual mega pixels. But, and this is a big "bug", noise, JPEG damage, lens limitations, etc. still limit the quality of the image you'd get vs. what you'd obtain with a high-quality - read: expensive, huge, and heavy - prime or zoom telephoto. Still, in the rare instances I need to use it, it does work for me. Just the ramblings of an old fool, YMMV. <grin> SignatureATM, aka Jerry "Whether You Think You CAN Or CAN'T, You're Right." – Henry Ford > The problem we have is with the fully automatic mode and the depth of > field - it really is very poor. For example, she enjoys taking indoor > photographs of our dogs - with the old Olympus most of the subject > remains in focus, but with the 350D we can perhaps get the nose of the > dog in focus but the rest is slightly out of focus. smaller aperture = deeper depth of field and bigger F number = smaller aperture The funny thing is I'm always trying to get a shallower depth of field - never heard of anyone wishing for a deeper one before. :) SignatureMark Mostly photography... http://www.marklauter.com > > The problem we have is with the fully automatic mode and the depth of > > field - it really is very poor. For example, she enjoys taking indoor [quoted text clipped - 7 lines] > The funny thing is I'm always trying to get a shallower depth of field - > never heard of anyone wishing for a deeper one before. :) Try an F1:1 lens, and shoot close up with it wide open. DOF should be in the region of <1mm :) > > The funny thing is I'm always trying to get a shallower depth of field - > > never heard of anyone wishing for a deeper one before. :) > > Try an F1:1 lens, and shoot close up with it wide open. DOF should be in the > region of <1mm :) :) Since I bought the Canon 50mm F1:1.8 I've been much happier. :) SignatureMark Mostly photography... http://www.marklauter.com > > The problem we have is with the fully automatic mode and the depth of > > field - it really is very poor. For example, she enjoys taking indoor [quoted text clipped - 7 lines] > The funny thing is I'm always trying to get a shallower depth of field - > never heard of anyone wishing for a deeper one before. :) Ever wondered why view camera lenes stop down to f/64 or even f/128? It's so they can get more depth of field. Ever done any macro photography? Again, you're nearly always fighting against limited depth of field. And when I take snapshots by available light, if I go for a group of more than two people I almost always suffer from the limited depth of field. SignatureDavid Dyer-Bennet, <mailto:dd-b@dd-b.net>, <http://www.dd-b.net/dd-b/> RKBA: <http://www.dd-b.net/carry/> Pics: <http://dd-b.lighthunters.net/> <http://www.dd-b.net/dd-b/SnapshotAlbum/> Dragaera/Steven Brust: <http://dragaera.info/> > > The funny thing is I'm always trying to get a shallower depth of field - > > never heard of anyone wishing for a deeper one before. :) > > Ever wondered why view camera lenes stop down to f/64 or even f/128? No, never wondered that - I don't lug a view camera around with me. ;) > And when I take snapshots by available light, if I go > for a group of more than two people I almost always suffer from the > limited depth of field. Use a higher ISO, Luke. <g> SignatureMark Mostly photography... http://www.marklauter.com > > > The funny thing is I'm always trying to get a shallower depth of field - > > > never heard of anyone wishing for a deeper one before. :) [quoted text clipped - 8 lines] > > Use a higher ISO, Luke. <g> Can't afford one; I'm already at 1600 for those, which was as far as that camera could go. (New camera last Friday, I can now get up to 3200, but it's "pushed" or whatever, not "real", as the camera documentation seems to say.) SignatureDavid Dyer-Bennet, <mailto:dd-b@dd-b.net>, <http://www.dd-b.net/dd-b/> RKBA: <http://www.dd-b.net/carry/> Pics: <http://dd-b.lighthunters.net/> <http://www.dd-b.net/dd-b/SnapshotAlbum/> Dragaera/Steven Brust: <http://dragaera.info/> > > The funny thing is I'm always trying to get a shallower depth of field - > > never heard of anyone wishing for a deeper one before. :) > > Ever wondered why view camera lenes stop down to f/64 or even f/128? BTW, this isn't the large format group - my comments here are, unless otherwise noted, within the context of dSLR systems. SignatureMark Mostly photography... http://www.marklauter.com > > > The funny thing is I'm always trying to get a shallower depth of field - > > > never heard of anyone wishing for a deeper one before. :) [quoted text clipped - 3 lines] > BTW, this isn't the large format group - my comments here are, unless > otherwise noted, within the context of dSLR systems. Sure. *My* point was that people were seeking greater depth of field. SignatureDavid Dyer-Bennet, <mailto:dd-b@dd-b.net>, <http://www.dd-b.net/dd-b/> RKBA: <http://www.dd-b.net/carry/> Pics: <http://dd-b.lighthunters.net/> <http://www.dd-b.net/dd-b/SnapshotAlbum/> Dragaera/Steven Brust: <http://dragaera.info/> > > BTW, this isn't the large format group - my comments here are, unless > > otherwise noted, within the context of dSLR systems. > > Sure. *My* point was that people were seeking greater depth of > field. True - but I don't meet many of them in my day to day. :) SignatureMark Mostly photography... http://www.marklauter.com Depth of field is a function of magnification, with the Olympus you have a small sensor, very low mag, a lot of depth of field. With the Canon, you have a bigger sensor, more mag , less depth of field. In application, the shorter the focal length of the lens the more depth of field, so on your Canon if you use the telephoto end you will get less depth of field than at the wide end. The Olympus will always give you more depth of field. Now add to this light, aperture, shutter speed and exposure index. For a certain level of light and exposure index on the camera there is a set of shutter speeds and coresponding aperture on the lens that gives the correct exposure. So if you are taking pics in your house and you have an exposure of f3.5 at 1/30 of a second, you can add depth of field by changing the aperture to f5.6 But that changes the shutter speed to about 1/10 of a second. There you will find it difficult to hand hold the camera. What can you do? Increase the ISO of the camera, if the original ISO was 100 go to 400, that will raise your shutter speed to 1/40 at f5.6. Again you may or may not be able to hand hold your camera at 1/40, but your dogs may not hold still enough either. Another way is to add light via your flash, photographing in under 10ft this can be very effective, but the light can be harsh. The suggestion that if you want more depth of field to set your lens on f8 or f11 and use A (aperture priority) auto is a good one. This will work outside but probably not inside without flash. But because of the small sensor, your Olympus will always have more depth of field. Tom Thanks very much for all the replies. After much experimentation and numerous tests I've found that Portrait mode seems to be the best compromise (along with a faster ISO). One strange problem though with Portrait mode - in low light conditions the flash won't fire. I have to pop it up manually with the flash button and then it will fire for all subsequent shots. Despite reading the manual I can't find a reason for this (but, as mentioned in various Internet reviews, the manual for this camera isn't that great). I assume that it's a 'feature' that I've missed? > After much experimentation and numerous tests I've found that Portrait > mode seems to be the best compromise (along with a faster ISO). After you get more comfortable with photography you'll probably never use any of the preset modes. I can't speak for the others, but I use Av and Man almost exclusively. matt wrote: > The lens we are using is the Canon EF 35-80mm zoom - I used to use it > on my old 35mm camera with no depth of field problems whatsoever. > Depth of field is a function of magnification, with the Olympus you > have a small sensor, very low mag, a lot of depth of field. With the > Canon, you have a bigger sensor, more mag , less depth of field. > In application, the shorter the focal length of the lens the more depth > of field, so on your Canon if you use the telephoto end you will get > less depth of field than at the wide end. The much larger sensor reduces DOF relative to the point & shoot camera's small one but relative to full frame 35mm film, the sensor is somewhat smaller than the film so it has somewhat more DOF... but the lens length is changed to a longer field of view, what was 35mm is now 56mm. Matt needs to buy a wider lens, a 22mm would be needed to get back the DOF from the old film camera. > The Olympus will always give you more depth of field. > Now add to this light, aperture, shutter speed and exposure index. For [quoted text clipped - 14 lines] > work outside but probably not inside without flash. But because of the > small sensor, your Olympus will always have more depth of field. |
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