@tjbr52:
1.] The acceptance & use of standardized 35mm film format stems has nothing to do with what the human eye can see. It stems directly from Thomas Edison's patent of his Kinetiphone in the early 1890's: Edison's aperture design defined a single frame of film at 4 perforations high. His film stock was manufactured by George Eastman (of Kodak fame), & distributed to Edison thru Blair Camera Co., where it was trimmed to Edison's specifications of 35mm, in order to fit the aperture & the sprockets designed to move the film forward. You can read about the history of 35mm in
this Wikipedia article.
2.] Stephanie is correct about the 50mm lens most closely mimicking what the human eye sees. Its field of coverage (40° horizontally, 46° diagonally) is roughly equal to what the human eye can view with relative clarity.
Before the advent of digital SLRs, the 50 mm lens were considered prime, & was the traditional starter optic & mainstay lens for photographers. An excellent article about using them now --
view linkHere's the technical explanation of horizontal planes of view, human eye compared to 50mm lens. Interestingly, this is from legal records thru the EFSEC of the State of Washington.
view link
"Field of View - Horizontal PlaneFor evolutionary reasons, the extreme perimeter of human vision is really only for sensing motion and large-scale objects (e.g., the lion suddenly approaching you from the side).
The central angle of view is approximately 40-60 degrees directly in front of the eyes and is what most influences human perception of a scene, as shown in Figure 2. Subjectively, this would roughly correspond with the angle over which a viewer could recall objects
from a scene if he/she had kept their eyes in the same position (Forum 2008).
A 35 mm camera equipped with a 50 mm lens takes a +/- 45 degree field of view in the horizontal plane and best represents and records the central angle within the normal human field of view (Nikon 2008).
Figure 2 illustrates the typical field of view that wide angle, normal, and telephoto lenses capture. The field of view captured by the 50 mm lens is 45 degrees and has the closest relationship to the central angle of the human field of view, without distortion of the object's
scale in the captured scene (Smardon et al. 1986)."