Linear Polarizers do nothing on a DSLR? I beg to differ!
Following my rant and my experience with my larger 67mm diameter polarizer, I headed back to the store and picked up two ‘throw away’ linear polarizers for my 52mm diameter lens total cost… $6.
After cleaning them up and tightening the glass fixtures I did my normal test (looking at an LCD screen and rotating it till the glass appears black) and one of them seems to turn a dark blue and not totally black, this one has probably been left on display somewhere and has been blasted out a bit… at $3 it is still probably useful as a backup. The other one looks fine in this regard and is in good shape in general, the rotation is a little loose but ok.
Now I took my camera out for a proper test and here are a few comparisons.
From left to right, that is Minimum, approximately half and full. I have attempted to equalize the exposure but as you see, the cloud and the sky look drastically different with more polarization
OK so far so good, it is good to note that the original raw at full polarization looks very artificial, with a deep deep blue sky, and white cloud, shooting like that is likely not what people are generally aiming for. The middle shot probably represents the correct(ish) setting.
Now for water shots. I found a duck who was occasionally getting hit in the face with waves, and fired off two shots timed to when the wave was just about to pass. There is no post processing on these, just a direct transfer to jpg.
A quite obvious difference and exactly what would be expected from a polarizer.
And finally a shot of the clouds, small amount of colour adjustment and post processing on this one.
Final remarks? Well I think there is definitely some misconception regarding how well linear polarizers work on a digital camera. I do not have a circular polarizer to compare against so I am not going to make a statement “Just go with linear there is no difference” But i will say that, the functionality of the filter itself is not at all effected by it being on a digital camera… indeed why would it be passage of light through glass and fundamental laws of optics didn’t change since digitals started replacing film did they? I will also state the limitations or problems that i can see
1) The accuracy of exposure is reduced, basically the linear polarizer messes up the way the camera performs metering and so you might expect a +/- 1 on the exposure, again I dont see this as a problem for anyone who is happy to use the functions of their camera.
2) Focusing – depending on the light level is sometimes problematic, again caused by how the camera auto focuses being effected by linear polarization. In my limited experience Iv not found this to be an issue. AND once again, I actually freely switch between manual and auto focus all the time, so it does not bother me in the slightest.
3) Colours – Obviously if you use inappropriate settings, images are going to look other worldly… but some people basically shoot like that permanently so this is more an observation than a limitation.