Quote:
Originally Posted by Peter Ward
Hey Stefan. It's because the focal plane of a converging light cone falls short by the stated amount with a plano element in front of a sensor.
The thicker the filter, the more the converging cone is refracted.
Yes, the refractive index of the filter also makes a difference, but likely an order of magnitude smaller.
Hope that sheds some light  |
Peter,
That would only be possible if the refractive index of the filter/window was less than 1. I never heard of such optical glass. As a rule of thumb, a plane parallel window, made of common optical glass, will EXTEND the focal plane by 1/3 of its thickness.
So I'm still stumped about what they are trying to say.