John Francis wrote:
On Fri, Sep 09, 2005 at 06:07:37PM +0200, Dario Bonazza wrote:
Isn'it it possible that a large rear element force rays perpendicular to
the sensor? This will allow a better image on the sensor and if such an
element is part of the lens design, it won't affect lens performance.
No. To a first approximation light rays from every part of the rear
element contribute to every point of the image. The larger the rear
element, the wider this cone of rays is, and so the more deviation
there is from the perpendicular (and the wider the range of angles,
which makes it hard to compensate by angling the sensor pits).
What you're saying is, the rear element really doesn't collimate the
light bundle, that about right?
Are you also saying it can't happen, according to the laws of optics as
you understand them?
I thought that was the reason for the odd shapes some lenses are ground
to, to set up the refraction so it DID control where the light went and
how it looked after it exited the last surface...
I'm not dissing you here. I am not capable of anything but the most
rudimentary ray tracing and today, so many years after I learned how,
not even that!
keith whaley
