Originally posted by Ron Boggs I couldn't care less about theories and math.
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But if you've never shot a variety of formats, there's no way you can actually understand. Sorry!
Is this an answer to me?
If so, I consider it to be inpolite and rude.
And I did shoot on a variety of formats and still I cannot disagree more.
"
Understanding" means understanding, not having seen something. Having seen something is "
Observing". You observe w/o understanding.
Understanding requires a certain level of theoretization allowing you to
predict things before you actually try it out. Which, in the case of optics, involves some rules which are shortest when written in the language of math.
So, I am sorry, but you cannot be more wrong. It was people which were able to
truely understand which gave you the toy named camera you have been gifted to use now.
To answer your question: Look up a text-book on lens design or classical optics. Read it. See that both, circle of confusion and f-stop value are determined by the optical focal length and the optical entrance pupil. And so is DoF. The entrance pupil is a virtual image of the aperture stop and already incorporates
any variation an optical design may have.
Therefore, an optical design cannot change how DoF depends on the f-stop. As I said, only Field of View and the diameter of the entrance pupil do.
This answer is final. I only will respond to you again if your tone gets a lot more polite.
Addition: I actually assume you have missed the trivial part of all answers given so far. You write:
Using a "standard" focal length, take a picture at f22 with a K10d and the same picture with your 67II at f22--tell me you can't see the difference in diffraction effect.
Well, standard lens means to keep constant the Field of View. Of course, then the aperture with 67II at f/22 is much larger than the aperture with a K10D. Because the aperture is
f/22 (as it actually says in bold letters). And f of a standard lens for a 67II is much larger than for a K10D. Divide by 22 and you'll understand. Maybe.
Originally posted by Sean Nelson ...which is why a 200mm lens has different depths of field when used on different sized sensors - it's field of view changes.
Yes, or if you crop into an image (a major source of confusion ...).
Things only appear to be complicated before they are understood.
Of course, a 200mm lens designed for 67II and designed for K10D still have identical DoF when used at the same body and using the same f-stop.