My misunderstanding/ confusion on (Crop factors) 50mm closet to the Human Eye?

[David Mullen ASC]

On 9/22/2022 at 3:03 AM, Martin Munthe said:

So to confirm what Hitch was talking about - I ran some of his films through a camera solve software tool that retrieves FOV meta data. Matching that to type of camera used and voilá! Psycho, Rear Window and so on (35mm open gate) is shot 50mm all through. And his VistaVision films are all shot using the 50 mm. He did not switch lenses to match FOV. Field of View was not a priority. His VistaVision films have about 10 more degrees of viewing angle. "Shrinking the equivalent of the human eye" or the other way around was probably not even something he thought about. My guess is he picked this up from the directors and cameramen at Babelsberg/UfA.

That's interesting, I figured he probably used a 50mm on his VistaVision cameras -- a bit like how the early CinemaScope films were shot on a 50mm but now with a wider field of view. But there's nothing special about the number "50" so there's nothing special about sticking to a 50mm when switching to VistaVision: he would have gotten the same image with a 35mm lens on standard 35mm as the 50mm on VistaVision, so same subject size, same relative sizes between subjects, same perspective, and the same field of view (just less depth of field with the VistaVision image). 

So there was no reason to stick to using a 50mm other than not understanding these issues; it's just because the number 50 has some sort of mistaken value at that point.

Relative sizes of objects to each other is based on camera placement relative to the subject, not focal length.  All focal length is doing is providing magnification / cropping.

[Robert Hart]

It might simply come down to what satisfied people at the time versus practical availability. 50mm to a 4:3 motion picture frame might be the same aesthetic crowd pleaser as the 85mm lens is to stills imaging although some stills folk preferred the 105mm for human portraits. 

[Nicolas POISSON]

John P. Hess has made a video about normal lens. He focuses on the "typical image size seen from a typical distance" approach. Interestingly, he gives some figures about those typical sizes and distances, which translate into field of views ranging from 20 to 40°. For S35, this means focal length between 32 and 66mm. For full frame, this means focal length from 50 to 100mm. This illustrates how approximate this concept is.

Edited July 5, 2023 by Nicolas POISSON