Archived posting to the Leica Users Group, 1998/04/30
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Chris Bitmead wrote: >It isn't possible! The human eye is not like a regular >camera/lens. The human eye itself is exactly like a lens. That's what it IS. There's no mystery there. You are confusing perceptual issues in the brain and retinal anatomy which have nothing to do with the actual focal length of the eye. When trying to get an idea of the approximate focal length of your eye, it helps to look through a rolled up piece of paper to keep you from confusing the wide angle of view of the human eye with its actual focal length, which is the issue here. The human eye can have such a huge angle of view at a given focal length when compared to the equivalent lens in front of a 35mm film frame because the "film" of the eye is a lot larger, proportionally. >Tell us how a scientist might >determine what length lens corresponds to the human eye? One of the many ways of determining the focal length of a lens is: 1/f=1/s+1/s' where f= focal length in cm, s=distance from object to lens, and s'= is distance from image produced to lens. Thus, s would be the distance from the object you're looking at to the front of your eye, and s' is the distance from the lens of the eye to the image produced on the retina (this changes as your eye focuses).