Hallöchen!
Gert van der Plas - Schrama writes:
> [...]
>
> Lensmakers try to make it easily corrected. As some lenses have
> mustache shape distortion no doubt some require more than linear
> compensation particular wide angle and fish eyes.
Well, you always have to make compromises. The most accurate
solution is a distortion field, which defines the lens error on
dozens, maybe hundreds of grid points. Somewhere between this and
the linear sliders is the best compromise. It may be a 4th order
polymonial, but the linear fit uses to be just *that* good that I
doubt that the best compromise should be so far away from linear.
Higher orders with more coefficients always fit your data better.
But they are also more unstable.
> [...]
>
> I also think my argument to allow non-radial factors for special
> lenses is still valid.
The by far most important non-radial error component is a
decentering, which needs to be tackled by a shift of the coordinate
system. I needed this shift once in 100+ lenses that I measured so
far. Everything beyond that is difficult to measure with the means
that are available to us, I think.
Tschö,
Torsten.
--
Torsten Bronger Jabber ID: torsten.bron...@jabber.rwth-aachen.de
or http://bronger-jmp.appspot.com
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