The Hoya HRT CIR-PL UV filter is a winner in my opinion. It has both the polarization and UV protection, but most importantly it does not cut down on the light reaching your camera sensor as much as many of the others. Together with its low cost, I think this is the filter every photographer should own.
The “HRT” in the name designates the filter’s high rate transparency film. In other words, the film that passes more visible light through the filter while still giving the polarization effect. How much more light? About 25% more or 1/3 stop. I tested this against my Singh-Ray LB warming polarizer and found that Hoya’s claim is valid.

Hoya HRT CIR-PL UV filter
The Advantages
This filter gives me a distinct advantage over my other circular polarizers. It allows more light through it, and it also provides UV protection. The UV effect is subtle, but I like it a lot. A UV filter is also known as a skylight filter. The UV effect is to block UV rays. As a result, the UV portion of this filter causes a slight warm cast to the photo. This is perfect for me because I have always liked the effect that comes from a warming circular polarizer.
I can take more shots in lower light than ever before. With my other filters, I would have longer exposure times, forcing me to use a tripod. This is just not always practical, so I would end up increasing ISO and getting noisy images. With this filter, however, I can shoot in lower light and at low ISO levels.
Even compared to the top of the line circular polarizing filter, this filter matches up nicely. Look at the transmissibility curves as tested by LensTip.com in Poland. They find the top of the line Hoya HD filter is closely matched by the Hoya HRT CIR-PL UV. The HRT film used on the filter allows nearly the whole spectrum through when not polarized (T1, red curve) and blocks almost all when fully polarized (T0 curve).

Transmission curve of the Hoya HRT CIR-PL UV filter. $36.

Transmission curve for the Hoya HD series of filters. $175.
With the Hoya HRT CIR-PL UV filter having equivalent transmission of the more-expensive Hoya HD3 CIR-PL filter, the choice becomes even clearer. Yes, the HD3 offers a stronger, more durable filter, but the functionality is what matters most, and the HRT CIR-PL UV is the same.
The Hoya HD3 CIR-PL is $175 where the equivalent performing Hoya HRT CIR-PL UV filter is a mere $36.
At such a low cost, I can afford to put this filter on all of my lenses. While it does not have a smudge-proof hardened glass like higher-end filters like the Hoya HD-series, the low cost makes it highly replaceable.
I seriously recommend this filter for any landscape or nature photography. It has worked well for me, and I believe it is sure to be of benefit to you as well.
Thank you for reading what I wrote — I hope you enjoyed it!
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