Camera filter holder calculator

Chris Molloy from New Zealand writes:

I’m about to embark on an epic (for me at least) hiking expedition, and, in the name of minimising pack weight, my SLR is staying at home and my compact camera is coming out to play. BUT one thing I was potentially going to miss was the ability to use a polarising filter (most compact cameras have no ability to mount filters on them and my Canon Ixus 900Ti is no exception). I wanted to find a way to hold a filter in front of the my compact’s lens in such a way as to: eliminate reflection from the rear of the filter; ensure the holder avoided blocking any of the sensors on the front of the camera, and; still be able to rotate the filter (a key requirement for using a polarising filter).

The obvious KISS solution was a cut-off cone that matched the diameter of my filter at one end and the lens surround at the other (loose enough so as not to impede the lens in any way). The depth of the holder needed to be great enough to clear the lens at it’s shortest/widest and longest/narrowest zoom. The holder was to be made of thin, black (to reduce reflectivity) plastic (waterproof/durable). The whole thing would be held together with black insulation tape, which is strong, but removable, if I ever want to recover the filter.

His filter holder calculator takes in some basic measurements and outputs SVG code for making your own custom filter holder.