les,

I understand about the field of view being dependent on focal length and image plane size. As the proud owner of a Nikon D90 and couple thousand dollars worth of lenses, I'm well aware that 50mm on a DX sensor has the equivalent FOV of a 75mm on an FX sensor. The factor is 1.5. For Canon APS-C format, the factor is 1.6.

The FOV you quoted is equivalent to a 70mm lens on a 35mm sensor. Which is why I say one must multiply by 1.4 to understand what apparent FOV you're going to get in terms of the most common interpretation of 50mm being mid-range on an SLR camera. It's going to look like a 70mm lens was used.

So, given that Poser doesn't offer us a second parameter to specify the image "sensor" size (FX, DX, APS-C, Medium Format, etc.) then we have to conclude that the "sensor" size was chosen and fixed by the developers. Further, I assume that they decided what sensor size to emulate not because of randomness or stupidity, but an understanding of what 50mm means to most people.

Now without any documentation, but with the understanding of decades of common standardization around 35 mm SLRs, what would a reasonable person expect is Poser's sensor size? Would it be sensible to assume it is 35 mm, since that is wildly the most common format of camera in use? I think so.

And for sure there are thousands of Poser users who mistakenly believe that is the case. Knowing that thousands of Poser users would have that expectation, I consider it a mistake that the crop factor for Poser is the square root of 2.

It is abundantly clear to me that the intention of the author of this bit of code had planned to make it 35mm. But whoever that was, they made a trivial mistake somewhere and accidentally included a multiplier that is the square root of 2.

I can't imagine that this was intentional. The crop factor of 1.414 compared to a 35mm camera does not correspond with any known camera. FX or "full frame" is 1 (same as 35mm). Nikon DX is 1.5. Canon APS-C is 1.6.

If I'm not right about this being a mistake, then what is your explanation for the square root of 2?

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)