Opinions on UV filters diverge a lot between photographers.
Some use them as protection for the front element, saying they won't affect IQ.
Some don't use them, saying IQ is lowered due to the "cheap" glass used on the filters.
Some use 10 dollars filters. Others use 60 dollars filters.
But how does an 10 dollars UV compares to an 60 dollars UV? Will they degrade IQ? I decided to test them today.
- Canon 40D
- 100mm f/2.8 Macro
- Hoya UV Standard filter (around 10 dollars. Got for free on the store I buy my lenses)
- Hoya PRO1 UV Filter multi coated (around 60 dollars in Brazil)
- Hoya Circular PL box as subject
How the test was performed:
- I decided to get my sharper lens to do this, but use it at its softest: f/2.8 @ MFD.
- I left the lens AF to the subject, then switched it to MF. That would avoid any focus change between the shots.
- Camera in Manual Mode, 1/20s, f/2.8, timer 2s. Same settings for every shot.
- No PP done to the pictures besides cropping to 100% and converting to JPEG with the same settings trough DPP.
Top is with no filter.
Center is with the cheap filter.
Bottom is with the Pro1 filter.
Here are the links to the 100% crops. I recommend you to open in different tabs so you can compare between:
http://farm4.static.flickr.com/3330/348 ... 6ca4_o.jpg
http://farm4.static.flickr.com/3375/348 ... de20_o.jpg
http://farm4.static.flickr.com/3305/348 ... dcbc_o.jpg
I can see pretty much difference in sharpness when using no filter. For my eyes, the image is MUCH more sharp without a filter.
I can't see much difference between an 10 and an 60 dollars filter tough.
If you think this test isn't worthy and have an suggestion of how I should perform it better, I'm open to suggestions.