[pkinchington (Peter (Kanga))]

Originally Posted by billdan

As Markus said, the closer to the sensor the shadow is, the smaller it is.

This formula is useful for locating shadows and/or halo's.

Distance from sensor (mm) = (p x f x d)/1000

Where p = pixel size in microns
f = focal ratio
d = diameter of shadow/halo in pixels

Thanks for the formula.
Cheers Kanga