paulkaye wrote in post #14983003
All this chat about DOF differences between crop and FF risks being confusing. The truth is that the only factors that determine DOF are focal length, distance to the subject, and aperture (for a given enlargement size in the final print). The frame size makes no difference, except that a crop sensor will of course 'crop' the image compared to the FF sensor.
To illustrate this, imagine you:
- mount a 50mm lens on a 40d and on a 5dii
- set both cameras at, say, 1m from a subject
- set the aperture to, say, f2.8
You'll find that the DOF from both cameras will be IDENTICAL. Of course, the crop camera would show less of the scene. Now, If you move the 40d back so that its field of view is now the same as the 5dii, then of course you've changed the subject distance and now the DOF on the 40d will be greater. But, the changed DOF is caused only by the changed distance, not the sensor size.
This is the clearest, most concise description of the differences between full-frame and aps-c DOF that I have ever read. It sums up and describes the situation with a minimum of distractions and clutter. That said, there are those who will argue with you until the cows come home. The experiment you have outlined would prove this, once and for all, to anyone who bothered to try it.
Alas, some people thirst more for argument than answers. I have had a few of these discussions. Just remember, if evidence, reason and logic don't persuade someone, they are by definition, unreasonable and illogical. I have posted photographs, with all measurement and EXIF data provided, only to have someone say that what they are looking at is not possible.
Stupidity is a condition the bearer has no control over. Ignorance is simply the lack of knowledge, easily corrected with a desire to know and understand. Refusing to believe that which you have evidence to verify, is intentional ignorance, which in my mind is the worst kind. You will run into intentional ignorance in DOF and crop factor discussions.
