Joined: Wed Oct 08, 2008 4:23 am Posts: 862 Location: Montreal, Quebec, Canada
I'm not expert in optic ... and very far from other in the forum in technical answer ... but for my own experience, I have tried about a lot of Filter found on Ebay before to stick with good one.
For low end price like fake Hoya or kind of "clear optic" company ... , the first thing you found with those filter is that the contrast is not there (where a Polarized should increase ...), huge lost of detail on good lens and high resolution sensor. Not constant coating ... meaning that you will have strange effect even if you tried to turn the filter at the correct position, there will never be a good degraded shade in your sky or water. Smooth turning filter for adjustment will not be there too on cheap filter (difference in plastic barrel instead of metal), and the small line to indicate the angle of the filter will not be there ... or the glass inside the filter will be loose that you will never be able to calibrate on that (in case usually it is better to use eye on the finder ... but with new live view technology I think only taking the picture could be the way to validate the effect). Some cheap filter I got for a few $$$ was feeling plastic instead of glass.
On my search for good filter, that old Minolta 55mm and 72mm was really good. and I have one of two B&W too. The good aspect of the Minolta is that the filter is larger that the thread mount ... meaning that you are sure that the filter will not bring vignetting but you are not able to put the hood, but I think hood are not a problem when polarized filter is there. With good filter like that I have made personal test when putting and removing the filter have not engage lost of Pixel peeper detail, and much more like you expecting from a Polarized filter it was giving me feeling that I have better detail.
But again, this is my own finding ... and probably David will come with better technical answer.
My answer will be mostly the same for UV filter ...
_________________ Frank A99, NEX 7 & 5 user( and less Minolta lenses...)
Joined: Thu Dec 18, 2008 5:04 pm Posts: 2025 Location: St. Louis, Missouri, USA
I agree with Frank, - Quality - both optical and mechanical, will cost more. However, you'll also pay more for 'good' names because they know you will, and they'll take advantage of that. Capitalism at it's finest!
Wouldn't it be more precise if a machine is doing it?
Btw, for $5 you might get a linear polarizer and it is said that the sensors for phase detect AF don't like it. So that's why there are circular polarizers that require an extra layer and which are more expensive. Dunno if the new CDAF based cameras like the NEX would be ok with a liner polarizer?
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