IF the type of camera we own is a DSLR, then we are used to exchangeable lenses and lens-attachments. One type of attachment that has always been available since the days of SLRs, is a polarizing filter of some sort.
But a DSLR differs from the older, film-SLRs, also, in having an auto-focus system which is physical, and which fails to work with linearly-polarized light, aka plane-polarized light. And so where ‘in the old days’, we used to buy linear polarizers, these days, we’d buy circular polarizers, for use with DSLR cameras. In the pursuit of photography, they do everything a linear polarizer used to do, and never prevent the auto-focus from working.
This also has as practical consequence, that it will be difficult in most localities, to find a photographic retail store, that still sells linear polarizers. Usually, such stores only sell the so-called Cir-Pols. Yet, because the linear polarizer has always been technically easier to design and manufacture, than a cir-pol, it only stands to reason, that the linear variety can still be bought somewhere. It’s just that retail stores need to pay their rent, and frequently can’t make a profit out of stocking those.
One place where one can certainly still buy those is on-line, which is where I just ordered one. And I did so, because I wanted to test the hypothesis of This earlier posting. In other words, where I’ve run into a self-imposed question which I cannot find the answer to, just by thinking about it, I now intend to find the answer, using the Scientific Method.
(Updated 02/21/2018 : )