From: Joseph Tainter <[EMAIL PROTECTED]>
If most films can resolve less than most lenses, and most scanners
can resolve less than most films, why are prime lenses considered superior
to good zooms? It would seem at first glance that the extra lens sharpness
of a prime would not translate into extra image sharpness.
... snipped ...
I respond:
I'm going out on a limb a bit here because I've never seriously studied the
math behind all this as it specifically relates to optics, but ...
In general, comparing two lenses, a lens with higher resolving capability
does result in more resolution on film even if the film has lower resolving
capability than both lenses. There is a good mathematical explanation for
this ... I wish I could give it ... but maybe a simple way to think about it
is this ... each component (lens, film, scanner, etc...) in the chain
between the scene and a print (or digital file) acts as a filter (in the
matematical sense) or transfer function. Think of these components as
neutral density filters and the system resolution as the amount of light
transmitted through the filters. You can see that if we represent the
resolution of the two lenses by 80% and 90% transmittance respectively and
the film as having 50% transmittance. The system transmittance (or
resolution) is 40% for the low resolution lens and 45% for the high
resolution lens. The lowest resolving item in the system certainly has the
greatest impact on the system resolution, but all the items in the system
will effect the system resolution.
Now, at what point does an increase in lens resolution make no practical
improvements in the system resolution? Well, that depends on the relative
resolutions of all the components in the system.
Someone jump in here if I've screwed this up.
Eric
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