Hoya, the biggest name in optical filters, have just introduced a thinner version of their circular polariser, so we got one in to test. The new filter has a slimmer mount making it really light and compact.
But before the test, lets look at what a polariser is and how it works. It's a filter that screws onto the camera lens to help reduce glare from reflective surfaces. The filter has a rotating front section that can be turned to adjust the strength of polarisation. In one position you'll see near enough what you would if the filter wasn't attached and when turned through 90 degrees you'll often see reflections disappear. This is useful for shooting through glass where you would see what's reflected from behind the glass rather than what's through it. The same applies to water. If you try to take a photo of fish in water without a polariser you will end up with a photo of reflections of the sky and surrounding trees etc. The polariser cuts out all of this allowing the subject below the surface to be visible. But a polariser also has a dramatic effect on blue skies making them highly saturated colours, like the photos you seen in travel brochures. It also cuts out glare from many materials including some types of leaves making greens more vivid.
So with this in mind we put the Hoya newbie to test. Three things have been done to reduce the filter thickness. First the filter thread has had a tiny amount shaved off, but not enough to prevent it attaching safely to the lens. The grip that's used to tighten the filter to the lens is also a touch thinner, again no problem here. The main space reduction is in the front part that you rotate to adjust the polarising effect. It's about a third the depth of our existing B+W polariser. The only problem in use is that the rim is so thin it's fiddly to turn, especially in cold when you lose feeling in your fingers or when wearing gloves.
The benefit from the size is it's hardly noticeable on the front of the lens and the weight saving will certainly help on larger filter thread sizes where the filter could potentially be a strain on the lens's autofocusing motor.
Nothing has been affected in terms of quality. There is no noticeable degradation of image quality when the polariser is attached and it works effectively. I used a 52mm version, which, even with normal thickness versions has never been a problem for autofocusing motors, but in a size of 72 or 77mm this will be a real benefit.
Test by Peter Bargh
A test through glass. The angle of the window was around 45 degrees and most of the reflections have been eliminated allowing a shot of the subject behind to be recorded.
The polariser has reduced the light reflected from the leaves making the greens more saturated.