Filters Not Good!

Started Oct 21, 2013 | Discussions thread
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jamesm007 Veteran Member • Posts: 5,656
Filters Not Good!

I told you so is what I hear people saying. –

I have always used filters on my lens (over 7 years now). Decent mid-high quality digital types for protection of the lens element (except WR lens) I also have CPL filters for every lens size I own( Cokin filters as well, but there OK). The filters stayed on my lens; sometimes for years. I would rather clean the filter than the lens. I did many tests years ago and proved to myself over and over there were no ill effects.

Some months ago I bought the Pentax DA35mm f/2.4 prime lens to go with my newish K-5 (still holding onto the K20D however). This seemed to me a tack sharp low aberration lens right from the start (f/2.4). I really liked the deep colors, contrast and sharpness. I bought two things for it after I was using it. One a lens hood, another a lens filter.

Pentax DA35mm f/2.4

I seemed to notice a slight degrade in IQ when I put the filter on. It was a good grade digital filter and I suspected perhaps I got a fake filter as I bought the filter from eBay. I did some tests on this and could find no difference. Every now and then I would do the test because it seemed like lower IQ however nothing. Same with or without. But I could see something? Anyways since I used those type filters for years I put away that 'thought' to the back of my head. I used that filter up until today. That lens was used less and less. I did not think anything about my filters bad or good.

I started to use and note I had focus problems under artificial light with my Sigma 17-70mm lens. There was no reason for the problems of not having a good pic at f/2.8 and 17mm. The K20D made tack sharp pics even to this day with that lens and the K20D. I started to entertain the idea my filters are old and need a good cleaning. That did not help. I was thinking the K5 might be very sensitive to light! I viewed several videos on YouTube showing the ill effects of filters and the tester seemed honest (using other cameras). I did a re-test today. Bam finally a repeatable test showing degradation from using a filter. Its with the K5 and DA35mm f/2.4.

Note the lamp reflection in the frame. I can repeat this over and over with my DA35mm f/2.4 and K5.

Go to full size to see it clearly

Now with the filter removed note how there is no more reflection of the lamp and the overall IQ is a bit better.

Go to full size, but its not there! With no filter!

Now the Sigma 17-70mm f/2.8-4.5. It now focuses as it use to, that is its good in the middle at 17mm f/2.8 and only the corners are soft! I took off all my filters. From my 77mm on my Sigma 10-20mm f/4-5.6 to my 49mm 35mm lens. Sans filter for me. The K5 is sensitive enough to show what filters can do good or bad it seems.

This may seem drastic and too much to blame on a filter. But the filter did harm focus. You have to understand at this short distance, f/stop (f/2.8), soft corners being the norm, with the Sigma 17-70mm f/2.8-4.5 all it takes is being off one click of the focus ring to get a poor result!

This also helps prove to me sometimes we see things that can’t be put into words nor measured easily with common resource of a enthusiasts photographer. You see an improvement, higher IQ, or lower IQ, but can’t prove it many times.

 jamesm007's gear list:jamesm007's gear list
Pentax K20D Pentax K-5 Sigma 10-20mm F4-5.6 EX DC HSM Pentax smc DA 55-300mm F4.0-5.8 ED Sigma 17-70mm F2.8-4 DC Macro OS HSM +13 more
Pentax K20D Pentax K-5
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