Problem: need to linear polarize excitation light path of a Nikon Ti.

Problem: Nikon's slider parts have empty holes that are too small for a filter and the other positions have ND filters that are epoxied in place.

Solution: use cardboard or foamcore board cut with a razor blade.


Yes, we know the filters need to be cleaned!

Left two panels show the polarizing filter with the orientation the same as in the exciatation light path. The red light is a bright spot on the ceiling.
Right two panels show filter rotated 90 degrees and light blocked from projection on paper taped to ceiling.