I thought a polarizing filter only lets through light of one polarity.
Thus if I have 2 polarizing sunglasses and look through both superimposed and rotate one it should completely block light at 90 degrees rotation. I've tried this and it works.
However, I have two of Massa lens polarizing filters and they only slightly reduce the light when thus superimposed and rotated. I complained to Massa and they claimed two superimposed filters rotated 90 degrees should block the light.
Looking on YouTube I saw that viewing a filter against a computer monitor, it will block the light completely when rotated if it is a good filter – e.g. Hoya filter was shown to do exactly this.
Does this mean that the Massa filters are defective? If not, are many so-called polarizing filters (other than Hoya) this bad at polarizing compared to polarizing sunglasses or can I get ones that polarize 100%?
I checked a similar topic but it does not look at the degress of polarizing affected: How do I choose a polarizer?