Originally posted by omega leader I don't think the polarizer is used nearly enough to warrent the price difference. I spent $115 for a non-coated polarizer (77mm) and have perhaps used it twice in a year. And both times I could have made do without.
I don't think that spending twice that is necessary.
But when you need your filter, you need it. I paid premium price for mine, use it at least half a dozen times a year, and have zero complaints. Compared to the cost of the rest of my kit, the cost was really rather low.
The real problem with uncoated or single coated filters (not just polarizers) is the flare you get if a light source actually touches the filter. Your image comes out much softer than it should, and with lower contrast. The flare moves the base black way up the histogram. It's not the light transmission as much as the flare that is the problem.
As to the circular/linear debate, it runs with me the same way as the lenses I choose to use. If Mr. Pentax says use a circular, I use a circular. It cannot do any harm, and might do good in the rare circumstance.
A long, long time ago, I read a comment from a pro photographer. He suggested that the only time you should buy a lens that is not the same brand as your camera is if the lens does something none of your camera maker's lenses will do, and you have a real need for it. Each time I have used a non-Asahi lens, I have been disappointed, and lost money when I sold it off to buy Asahi Optical's glass for my camera. Your Mileage May Vary, as they say.