I saw that before.. but what really threw me today is the one guy claiming that focal length doesn't affect dof... maybe I read it wrong.. but ugh.
Focal length can affect DoF - it just depends on what else you do or do not hold constant. If you change focal length without changing subject distance, you're changing DoF. If you change subject distance without changing focal length, you're changing DoF. In each case, you're changing the magnification - the size of the subject. But if you keep the size of the subject constant (e.g., move closer as the focal length gets shorter), then DoF remains constant for a given aperture - that's why the statement that DoF depends on magnification and aperture is a better way to phrase it.
Put another way, DoF is determined by magnification and aperture, and magnification is determined by focal length and subjet distance.
A lot of people seem to have difficulty grasping this concept. Including some who think they know better in this thread. Its shown quite well in this article.
I don't see how the context of the article would contradict anything said in this thread.
The article studies "zooming by feet", while keeping the same sensor format.
The thread discusses changing sensor formats, while keeping the perspective intact.
I'm not sure if you are thinking that I claimed or implied that "the context of the article would contradict anything said in this thread". Au contraire what I was saying was that some people don't seem to grasp this simple relationship, the subject of the article I linked to. It is rather counter intuitive and many people have not grasped the link. I thought the article was a good clear explanation that restricted itself to a relevant and concise description, without going of at a tangent into irrelevant areas as so many do. It was jdramirez who questioned what someone had said. (and pleased don't read that to be a criticism of jdramirez from my point of view he was just asking for clarification and there is nothing wrong with that.)