Originally posted by tsdh
Don't worry, Jed is not around.
Not around? I don't know about that. But if this keeps up, I'm going to be forced out of here.
Originally posted by tsdh
Don't worry, Jed is not around.
Originally posted by ckiang
If you take a shot using a 35mm lens, and crop a 50mm equivalent out of it, DoF is that of a 35mm lens.
Originally posted by nhyone
Depends on your reproduction ratio. If you have to enlarge it more (due to the crop), I would expect the DOF to be less.
Are you offended?Originally posted by Jed
Not around? I don't know about that. But if this keeps up, I'm going to be forced out of here.
CK, I think nhyone has a point. The size of the final print you want will directly influence the maximum acceptable circle of confusion size, and thus in a sense influence DOF. As such, a significant smaller print may well yield a greater "acceptable" DOF for the same negative. Don't forget, how we perceive the "depth" in DOF is ultimately pretty subjective, and largely dependent on the print size and viewing distance.Originally posted by ckiang
Why would that be so? DoF is never dependent on reproduction ratio. DoF of a shot taken with a 35mm will be that of a 35mm regardless of whether the final print is 4R, 8R or even 20x30.
Originally posted by Midnight
CK, I think nhyone has a point. The size of the final print you want will directly influence the maximum acceptable circle of confusion size, and thus in a sense influence DOF. As such, a significant smaller print may well yield a greater "acceptable" DOF for the same negative. Don't forget, how we perceive the "depth" in DOF is ultimately pretty subjective, and largely dependent on the print size and viewing distance.
Originally posted by tsdh
Are you offended?
Originally posted by ckiang
If I didn't remember wrongly, Circle of Confusion and final print size are not related as well. It only affects the acceptable DoF on the film itself.
You have a point by saying that DOF will be narrower for that cropped image. Yes, that is true. But you have to take note that the reduction of DOF in the cropped image still can't be as narrow as the DOF of the long lens (to achieve the same magnification). It is negligible as compared to the reduction of DOF vs focal length.Originally posted by nhyone
Yes, for a given film size, it is generally assumed that the reproduction ratio will not affect the DOF, because the viewing distance increase.
However, circle of confusion is based on how much enlargement is required for the normal print size and "normal" viewing distance.
Cropping means you are in effect using a smaller film format. You will need to enlarge more to get the standard print size.
A picture is worth a thousand words!Originally posted by tsdh
But you have to take note that the reduction of DOF in the cropped image still can't be as narrow as the DOF of the long lens (to achieve the same magnification). It is negligible as compared to the reduction of DOF vs focal length.
I read this article before, although I have totally forgotten about it.Originally posted by Darren
To confuse the discussion even further , here is an article on DOF which is very interesting reading.
What he presented is true. And you're right, see the variables carefully. DOF will be constant for all focal length, if you can keep the object size the same by altering camera-to-object distance.Originally posted by nhyone
I don't know if what he presented is true or not, since he only gave empirical evidence. However, no one seemed to have pointed out his flaws, if any.
In any case, it may be confusing, but there is no contradiction. See carefully which are the variables and which are the constants.