Aside from removing reflections from water and glass, there is nothing that makes your colour pop, and your blue sky more blue than a polarizing filter. Polarizing filters are among the most expensive filters, except the old linear kind, which I believe nobody makes any more, but are available in abundance in the used market at very low prices. As anyone who knows the difference between a linear and circular polarizing filter will tell you, using a linear polarizing filter with auto focus cameras has the side effect of unreliable metering and focusing. I don't doubt that linear polarizing filters affect auto focus cameras, but how, or how much?
I decided to give it a try today. I mounted a Hoya linear 58mm polarizer on the Canon EF-S 18-55mm kit lens, and headed to Ontario Place and give it a try. I have taken over 375 RAW pictures and a few minutes of HD video, and here is what I have found.
For the most part, AF and Metering are not affected, and if it did, I didn't see much difference to notice. The linear filter produced the same effect as the circular version. Through out the day, I had only encounter focusing hesitations near the end of the day, where I was taking pictures with the sun shining directly into the lens. The lens did managed to achieve focus at the end.
So, my understanding is that under certain situations, linear polarizing filter does affect the focusing. But for 99% of the time, it works fine with auto focus cameras.
Cinesphere -- Canon Digital Rebel 550D (T2i) & 18-55mm Kit Lens. Embiggen.
Reflection -- Canon Digital Rebel 550D (T2i) & 18-55mm Kit Lens. Embiggen.
Wheels -- Canon Digital Rebel 550D (T2i) & 18-55mm kit lens.