DOF and Cropping take 2

Started Feb 11, 2014 | Discussions thread
falconeyes Senior Member • Posts: 1,453
Re: Awaldram

awaldram wrote

As to Falconeyes white paper I said it was unproven and thefore made up, It's his view and like most things has stuff I agree with and stuff I don't but if unproven its all conjecture.

I just see this now. Didn't know people exist who consider it a conjecture. However as I wrote in the white paper, I went through the math to proove every statement I make in the paper. So, it isn't a conjecture. And as it is easy to proove, just textbook exercise level, I never saw a point to bother readers with the math. They either understand (and are easily able to replicate) the math or they don't. Moreover, I had extensive private communications about it and its math was never challenged (equations need a minor modification if you drop the assumption of small magnification).

I really think the problem is one of language. E.g., terms "exposure", "illuminance", "luminance" and "luminous flux" are sources of confusion (I don't exclude my white paper here because I didn't anticipate this problem).

Esp. exposure should be avoided or clearly defined, e.g., if it represents an EV or a LV.

Another point is what "equivalent" means: It does not mean that, e.g., a change in sensor size or a crop changes a lens' focal length. It does mean that, for any given camera 0 with settings exposure time t0, focal length f0, aperture n0, sensitivity iso0, and sensor size s0, another camera 1 does exist (with settings t1, f1, n1, iso1, s1) where t0=t1 but all other parameters different. And where both camera 0 and 1 produce indistiguishable images, making both parameter sets "equivalent", in the mathematical meaning of equivalence classes. And as s0 and s1 differ, this may then be an ideal starting point in a reasoning about the impact of sensor size on produced images.

Regarding this thread, I wonder what is discussed actually. There seems to be a basic consensus. I think what remains is different use of words and assumptions about possible hidden agenda of some participants. Which is funny as the underlying facts are too simple to spend more than, say 3 posts

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