--- "Singh, Sarbjit (S.)" <[EMAIL PROTECTED]> wrote:
> 1) The effective focal length of human eye
> is between 13-16mm, and the effective
> numerical
> aperture is about f3 to f4.
I would think that since focal length is also a
geometric parameter, the size of the eyeball, which is
not same in every individual (we are not clones, not
yet ;> ) will make it difficult to quantify that
precisely. A range based on statistical analysis would
be more like it.
As regards the aperture: a very scared person will
have eyes dilated, or in low light the pupils dilate a
lot - here again the aperture is varying. Variation
may also be different in different people. Since
aperture notation is a relative quantity (i.e. it is
realized as a ratio related to the focal length),
again if the focal length is varying in individuals,
so will the effective aperture range.
> 4.) The retina ASA, it far exceeds any existing
> high
> speed films
If it is possible to safely look at a bright light
source, it will be noticed that the pupils become like
a "pinhole". Even then the scene can be visible and
interpretable by the human brain. Each person will
have differring threshold levels for such brightness.
I would compare the human eye more to a digital sensor
rather than a film because whereas the film has a
fixed ASA, a digital sensor's ASA can be varied in
different situations - the threshold either way being
different for different individuals.
- Harman
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