01-16-2012, 12:27 PM
[quote name='Rover' timestamp='1326707581' post='14896']
My understanding is that the greater DOF on APS-C comes not from the lens somehow "losing" aperture (which it doesn't) but from the fact that the actual focal length (which is one of three primary factors for DOF) is not changing and therefore is shorter than what you would've been using on 24x36 format (unlike when you're using an extender that narrows the aperture and adds focal length by changing the optical construction of the lens system). Guess it could be verified by shooting same lens on different sensor sizes at identical apertures and distances, then cropping the larger format image to match the smaller one's framing - it's probably going to be identical WRT DOF and perspective. Why the heck should it not - it's the lens that builds the image, the camera only catches it, and how much of it actually makes it into the image is the only thing that differs with sensor sizes.
I guess Brightcolors is going to disagree, though. I wish I could do some testing to learn this for myself but I only have one camera, and the APS-C NEX-3 I have access to cannot mount Canon lenses. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='
' />
[/quote]
What I wrote is correct, and you are missing something important. You are thinking of ONE lens on different formats.
We are talking about two different lenses on the same format.
Comparing one lens on different formats makes no sense. The field of view will be different, so there is nothing to compare expect that different field of view. APS-C will actually have a more shallow DOF impression in this scenario anyway, not more.
When we compare EQUIVALENT fields of view (so, different lenses) on different formats, what we should look for is equivalent apertures, not f-values. It is the size of the aperture which more or less determines the DOF. The f-value is just focal length divided by the aperture size. Anyway, I think I am confusing you more, here.
[quote name='Rover' timestamp='1326707581' post='14896']
The 60 is better because it's F/2 for most purposes except maybe DOF calculation - most importantly for available light shooting. Depends on more than just that, the relative distances (camera-subject and subject-background) as well.
[/quote]
One frames a subject (if one is a photographer), one is not nailed to the ground in one fixed position, so shooting with different focal lengths will still make the framing leading, not the distance from the photographer to the subject.
My understanding is that the greater DOF on APS-C comes not from the lens somehow "losing" aperture (which it doesn't) but from the fact that the actual focal length (which is one of three primary factors for DOF) is not changing and therefore is shorter than what you would've been using on 24x36 format (unlike when you're using an extender that narrows the aperture and adds focal length by changing the optical construction of the lens system). Guess it could be verified by shooting same lens on different sensor sizes at identical apertures and distances, then cropping the larger format image to match the smaller one's framing - it's probably going to be identical WRT DOF and perspective. Why the heck should it not - it's the lens that builds the image, the camera only catches it, and how much of it actually makes it into the image is the only thing that differs with sensor sizes.
I guess Brightcolors is going to disagree, though. I wish I could do some testing to learn this for myself but I only have one camera, and the APS-C NEX-3 I have access to cannot mount Canon lenses. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='
' />[/quote]
What I wrote is correct, and you are missing something important. You are thinking of ONE lens on different formats.
We are talking about two different lenses on the same format.
Comparing one lens on different formats makes no sense. The field of view will be different, so there is nothing to compare expect that different field of view. APS-C will actually have a more shallow DOF impression in this scenario anyway, not more.
When we compare EQUIVALENT fields of view (so, different lenses) on different formats, what we should look for is equivalent apertures, not f-values. It is the size of the aperture which more or less determines the DOF. The f-value is just focal length divided by the aperture size. Anyway, I think I am confusing you more, here.
[quote name='Rover' timestamp='1326707581' post='14896']
The 60 is better because it's F/2 for most purposes except maybe DOF calculation - most importantly for available light shooting. Depends on more than just that, the relative distances (camera-subject and subject-background) as well.
[/quote]
One frames a subject (if one is a photographer), one is not nailed to the ground in one fixed position, so shooting with different focal lengths will still make the framing leading, not the distance from the photographer to the subject.