Archived posting to the Leica Users Group, 1998/04/29
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Eric Welch wrote: > > >Since the angle of "normal" visual perception in humans agrees to the > >overlapping impression from both your eyes, the angle is definitely > larger > >than from a 50 mm (it agrees to a 35), even if one eye covered an area of > >only 47 deg (which is not true). > > What I objected to is that this claim that normal lenses can't be defined > becuase the angle of vision is not as narrow as a "normal" lens. What I > said was that the overall impression left by a 43mm lens most closely > represents what we look at with our eyes because of magnification. If he > doesn't want to believe it, fine, but that doesn't make it right, or any How will I determine the magnification of a 43mm lens? It is impossible to say that a 43mm lens gives 1x or .5x or 2x or any other number of magnification. Tell us how a scientist might determine what length lens corresponds to the human eye? It isn't possible! The human eye is not like a regular camera/lens. "The greatest difference between human perception and a camera lies in the way the brain builds up and recognies an image. In each eye, the resolution falls away sharply from the fovea, whwich is smaller than a pinhead and covers an angle of only 1.7 degrees. The views from both eyes overlap and combine. Although such a view is fine for concertrating the attention on one part of the scene, it would be useless for taking in the whole sweep of, say, a landsscape, were it not for the way in which the eye works. While we are rarely conscious of it, the eye actually scans a scene constantly with small, jerking movements that each last only a few milliseconds. By means of these saccadic movements, as they are called, the eye and brain bulid up a sharply perceived pattern of a large scene, in a large way quite unlike that of a camera." > reason to denigrate people for using the term "normal" for generally > accepted reasons, even if the reason isn't all inclusivly correct. No-one is denigrating anyone for using the term normal. I'm just pointing out that what is called a normal lens is nothing to do with the human eye. - -- Chris Bitmead http://www.ans.com.au/~chrisb mailto:chrisb@ans.com.au