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#21
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This DOF thang
David J. Littleboy wrote:
"Stacey" wrote in message ... Severi Salminen wrote: Most pictures taken with wide angle lenses DO have different perspective than pictures taken with long lenses. Still one should understand that the reason is not the focal length but the practical need to usually alter the shooting position when changing focal length. What helped me figure this out was doing macro work. When you start working at high magnification of small objects, all this "Short lenses have more DOF" etc quickly are seen for what they are, untrue. "Short lenses have more DOF" is quite true for normal photography _at the same f stop and same subject distance_. When you do macros, you don't keep the subject distance the same. (And the definition of "subject distance" becomes problematical at close distances.) Eaxctly, you aren't limited by infinity so it's easy to understand what's really going on. Plus it's easier to move 6 inches rather than 60 yards! :-) (I seem to recall discussion to the effect that DOF stays the same for the same magnification. So if you switch from a 110mm lens to a 55mm lens at the same subject distance, you get four times the DOF at the subject location, but if you halve the subject distance for the 55mm shot, the DOF should remain the same. I think. Corrections welcome for this _same format_ comparison.) You're exactly right. The lens focal length makes no difference or else everyone would want short length macro lenses. If you fill the frame with the subject, the focal length doesn't change the DOF, just the subject to camera distance. That's why a short tele makes for a good macro lens, you get some room for the lighting. 120mm on medformat works great. -- Stacey |
#22
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This DOF thang
"Gregory W Blank" wrote in message
Vladamir30 wrote: But then that's the whole idea behind telephoto lenses,....is it not? To flatten and compress distant subjects? Rather than making expansive wide angle images. "Telephoto lenses" (by which I assume you mean a long focal length lens, not a true telephoto lens) don't compress and flatten distant subjects and wide angle lenses (i.e. short focal length lenses) don't make "expansive" images. The compression and "expansiveness" you observe when using these lenses is a result of your camera position And the magnification/FOV they provide. In landscape use they do compress the image and this become confusing because infinity isn't something that can be changed i.e. moved closer or further from the camera.. It can be magnified with a lens change which does end up compressing the scene. -- Stacey |
#23
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This DOF thang
"Gregory W Blank" wrote in message
Vladamir30 wrote: But then that's the whole idea behind telephoto lenses,....is it not? To flatten and compress distant subjects? Rather than making expansive wide angle images. "Telephoto lenses" (by which I assume you mean a long focal length lens, not a true telephoto lens) don't compress and flatten distant subjects and wide angle lenses (i.e. short focal length lenses) don't make "expansive" images. The compression and "expansiveness" you observe when using these lenses is a result of your camera position And the magnification/FOV they provide. In landscape use they do compress the image and this become confusing because infinity isn't something that can be changed i.e. moved closer or further from the camera.. It can be magnified with a lens change which does end up compressing the scene. -- Stacey |
#24
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This DOF thang
Stacey wrote:
"Gregory W Blank" wrote in message Vladamir30 wrote: But then that's the whole idea behind telephoto lenses,....is it not? To flatten and compress distant subjects? Rather than making expansive wide angle images. "Telephoto lenses" (by which I assume you mean a long focal length lens, not a true telephoto lens) don't compress and flatten distant subjects and wide angle lenses (i.e. short focal length lenses) don't make "expansive" images. The compression and "expansiveness" you observe when using these lenses is a result of your camera position And the magnification/FOV they provide. In landscape use they do compress the image and this become confusing because infinity isn't something that can be changed i.e. moved closer or further from the camera.. It can be magnified with a lens change which does end up compressing the scene. When discussing about this "compression" you should define whether you mean it in engineering or artistic sense. For an engineer, no such thing happens as a funcition of focal length. You can get the same effect by enlarging a part of a wide angle shot. The quality will be poorer, because there is more magnification, though. For an artist the effect is real, but the artist is composing in real time through the viewfinder, and then the wide/tele difference can be seen easily. But it's just an artistic impression. -- Lassi |
#25
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This DOF thang
Stacey wrote:
"Gregory W Blank" wrote in message Vladamir30 wrote: But then that's the whole idea behind telephoto lenses,....is it not? To flatten and compress distant subjects? Rather than making expansive wide angle images. "Telephoto lenses" (by which I assume you mean a long focal length lens, not a true telephoto lens) don't compress and flatten distant subjects and wide angle lenses (i.e. short focal length lenses) don't make "expansive" images. The compression and "expansiveness" you observe when using these lenses is a result of your camera position And the magnification/FOV they provide. In landscape use they do compress the image and this become confusing because infinity isn't something that can be changed i.e. moved closer or further from the camera.. It can be magnified with a lens change which does end up compressing the scene. When discussing about this "compression" you should define whether you mean it in engineering or artistic sense. For an engineer, no such thing happens as a funcition of focal length. You can get the same effect by enlarging a part of a wide angle shot. The quality will be poorer, because there is more magnification, though. For an artist the effect is real, but the artist is composing in real time through the viewfinder, and then the wide/tele difference can be seen easily. But it's just an artistic impression. -- Lassi |
#26
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This DOF thang
"Stacey" wrote in message
... I never said it wasn't. John was the one who said at the -same F/stop- the DOF was the same. Now let's put this back into context. That was not exactly what I said. I made particular requisites concerning print size (and by inference, same COC). Apparently I was wrong, but in a more complex proposition that simply the above. |
#27
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This DOF thang
"Stacey" wrote in message
... I never said it wasn't. John was the one who said at the -same F/stop- the DOF was the same. Now let's put this back into context. That was not exactly what I said. I made particular requisites concerning print size (and by inference, same COC). Apparently I was wrong, but in a more complex proposition that simply the above. |
#28
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This DOF thang
jjs wrote:
"Stacey" wrote in message ... I never said it wasn't. John was the one who said at the -same F/stop- the DOF was the same. Now let's put this back into context. That was not exactly what I said. I made particular requisites concerning print size (and by inference, same COC). Apparently I was wrong, but in a more complex proposition that simply the above. And also more complex than Brain is making it. I think you are closer to the truth in practice than he is. -- Stacey |
#29
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This DOF thang
jjs wrote:
"Stacey" wrote in message ... I never said it wasn't. John was the one who said at the -same F/stop- the DOF was the same. Now let's put this back into context. That was not exactly what I said. I made particular requisites concerning print size (and by inference, same COC). Apparently I was wrong, but in a more complex proposition that simply the above. And also more complex than Brain is making it. I think you are closer to the truth in practice than he is. -- Stacey |
#30
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This DOF thang
Lassi Hippeläinen wrote:
Stacey wrote: "Gregory W Blank" wrote in message Vladamir30 wrote: But then that's the whole idea behind telephoto lenses,....is it not? To flatten and compress distant subjects? Rather than making expansive wide angle images. "Telephoto lenses" (by which I assume you mean a long focal length lens, not a true telephoto lens) don't compress and flatten distant subjects and wide angle lenses (i.e. short focal length lenses) don't make "expansive" images. The compression and "expansiveness" you observe when using these lenses is a result of your camera position And the magnification/FOV they provide. In landscape use they do compress the image and this become confusing because infinity isn't something that can be changed i.e. moved closer or further from the camera.. It can be magnified with a lens change which does end up compressing the scene. When discussing about this "compression" you should define whether you mean it in engineering or artistic sense. For an engineer, no such thing happens as a funcition of focal length. You can get the same effect by enlarging a part of a wide angle shot. The quality will be poorer, because there is more magnification, though. For an artist the effect is real, but the artist is composing in real time through the viewfinder, and then the wide/tele difference can be seen easily. But it's just an artistic impression. Yep what he said.. This is a subject that can be WAY over analized and it's better for someone to just shoot some film and figure out how to use DOF to their advantage from actual use. -- Stacey |
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