Hoya's polariser that incorporates a UV filter too
We recently reviewed Hoya's high-specification HD circular polariser, and now we're going to have a look at Hoya's latest polariser offering, the HRT, or High Resolution and high Transparency, circular polariser. First, let's recap on the uses of polarising filters. You can use a polarising filter to enhance the density and contrast of blue skies and cloud formations, reducing haze to an extent. Another important and handy use of polarisers is to cut out reflections in windows, shiny metallic surfaces and on the surface of water.
Unsurprisingly, polarisers are popular with landscape photographers, although you do have to be careful with the rotational orientation of the filter as it can cause an unbalanced darkening of the blue in the sky, concentrating the depth of the blue into a corner of the frame, which looks unnatural. Many inexpensive polarising filters have a cool tint and this can result in a blue-black tone to skies, which can look oppressively cool compared to the real thing. The problem is worse when at altitude, where there is more ambient UV light, and at sea level where there is a lot of water, snow or ice, concentrating UV light through reflection, resulting in blue shadows and/or blue casts. In these conditions the use of a polariser may be required, but often this will amplify the cold blue cast caused by excessive UV light. Hoya's answer is its new HRT polariser, which combines a UV filter with the latest generation in circular polarising films, apparently developed for 3D cinema glasses. The result is a lighter tint in the filter as it lets more light through and also less of a blue cast, while the UV filtration moderates blue casts.
(Above) Left - a 77mm Hoya HRT CIR-PL UV filter, top - Hakuba CIR-PL, bottom-right - Hoya HD CIR-PL. Note the darker and cooler tint of the Hakuba filter.
(Above) Both the Hoya filters have useful rotational reference marks (the triangle left of the word 'Hoya'). The HRT filter, unlike the much more expensive Hoya HD, does not have a slim line ring, or any anti-reflection coating.
Comparisons
This review was fast-tracked because of some unusually good weather here in Hemel Hempstead! As you can see in our comparison images below the sky was very obliging, although actually a few white fluffy clouds would have been welcome.
The four images below were all taken using the camera's metering, and are produced from in-camera JPEG files, with automatic white balance. No tonal changes have been made; the images have simply been re-sized for this web page. Eagle-eyed readers may spot that the aperture setting in the first image is f/6.3, while the others are at f/7.1. Although there is a one third stop difference, the exposure is correct, according to the camera, in all the shots:
(Above) Without a filter fitted. ISO 100, 1/400th, f/6.3
(Above) With the Hoya HRT CIR-PL UV filter fitted.ISO 100, 1/125th, f/7.1. The reflections on the water surface of the canal have been suppressed, while the sky is a darker blue than before. Depending on how you align the rotation of the filter the density of the sky can be a bit lop-sided; here it's darker to the right with the filter fitted, but it's even without the filter. The polarised image also looks a bit more saturated and is slightly warmer in tone.
(Above) With a Hakuba CIR-PL filter fitted.ISO 100, 1/100th, f/7.1. With the Hakuba polariser fitted, which is representative of cheaper polarising filters, the tone is cooler. As it's darker than the Hoya HRT, it needs a third of a stop more exposure, and two thirds more than the Hoya HD.
(Above) With a Hoya HD CIR-PL filter fitted.ISO 100, 1/160th, f/7.1. The Hoya HD is in between the HRT and the Hakuba in terms of image warmth and I detect a touch more contrast, too.
A better test would have been to go skiing, mountaineering, or sailing. Alas, we had to make do with a sunny later winter day in Hemel Hempstead. However, I can see that the Hoya HRT filter has potential for keeping excessive blue casts under control in UV-challenging conditions. It's certainly a much better proposition than sandwiching a UV filter with a conventional polariser, which risks flare and ghosting, especially when photographing against the light. It's a shame that the HRT range of filters aren't anti-reflection coated like the Hoya HD range, but as the HRT range is significantly more affordable than most coated polarisers, that's fine by me.
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