OM4Ti@xxxxxxxxxxxxxxxx wrote:
I know this is straying from the original intent of the thread.
Still seems on topic to me.
The High Refraction Index plastic lenses used is eyeglasses are nowhere near
photographic quality. They do not refract evenly across the visible
spectrum.
This is true of glass lenses as well, and in fact, of any single element
lens, regardless of the substance of which it is made. The only
difference is in the degree of dispersion. Back about 40 years ago when
I briefly studied optical physics, that was a function of the refractive
indices of the 2 media at the boundary where refraction occurs.
Refractive index, in turn. is dependent on the speed of light through
the medium. The bending, or refraction, is the result of light crossing
the boundary where its speed changes. Has something changed since then?
Is my memory faulty?
One of the reasons for multi element lenses has always been to use lens
elements of different refractive indices to put the different
wavelengths 'back together' through complementary dispersions.
It seem I remember reading that one of the Kodak single use cameras had
a 3 or 4 element lens with molded plastic aspheric elements labeled as
an Ektar which Pop Photo or somebody said made remarkably sharp images a
major step above other disposables.
It is interesting how people, myself included, tend to have prejudices
about materials, rather than evaluating the actual results of their
application.
Moose
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