Protective filter… or not? I say beware of filter quality.

Started Apr 15, 2014 | Discussions thread
Flat view
JohnFrim Contributing Member • Posts: 572
Protective filter… or not? I say beware of filter quality.

I know this debate has gone on forever and will not likely end any time soon. My intent here is not to rekindle such discussion, but rather to show that a cheap filter may not be a good idea.

I have always believed in using a protective filter for all those good reasons (prevent accidental damage, frequent cleaning, etc) AND because I believed that a (good quality) filter will not degrade an image. Further, when you see Kurt Munger's Dirty Lens article you kind of think that anything really close to the lens probably does not affect the image quality a great deal. Finally, we have all taken photos through dirty windows, and we know that holding the camera close to the window greatly reduces the effects of the window dirt.

I have a few Minolta lenses from my Maxxum days, so I pulled out my 75-300 mm Big Beer Can the other day to shoot some wildlife on my A57. The lens has not been used for many years, but I have always taken good care of my equipment and the lens looks like new. The filter on the front is an Optex 55 mm HAZE(UV) and it did not appear "overly" filthy, but it did appear to have a film of sorts.

I was VERY disappointed with what I was seeing on the LCD display when I magnified the images. Thinking it was perhaps just poor focus I took several shots, but they all looked bad. I did not have my tripod along, but I decided to shoot a few photos of a distant scene with the lens sitting quite solidly on my thighs while sitting on a bench. Shutter speeds were reasonably high to stop motion blur on Day 1, and very high (with elevated ISO) on Day 2.

The first two photos below are with the dirty filter.

Day 1, dirty filter.

Day 1, dirty filter.

The next image below is with the filter removed and is noticeably sharper.

Day 1, no filter.

I went home that day and cleaned the filter several times with lens cleaning fluid and a microfiber cloth. It actually took several fairly aggressive attempts to get the film off both surfaces of the filter, as seen by angling it against the light. It finally looked pristinely clean.

A few days later I returned to the same spot and took photos with and without the filter.

Day 2, clean filter.

Day 2, no filter.

I don't think anyone would argue that the images with NO FILTER are definitely sharper. In fact, there is not a great deal of difference between the dirty and clean filter shots. Some might even say the clean filter photo is actually not as sharp as some of the dirty filter photos, so maybe there was a slight focus error. Let me just say that I took several additional photos at closer range using manual focus with magnified view to get good focus and the results are basically the same: this cheap filter really causes problems.

I still have a few other older Minolta lenses to play with, all with older and cheaper filters than what I have on my Sony lenses. I am going to compare with and without both cheap and expensive filters, but right now I am convinced that cheap protective filters might not be a good idea.


 JohnFrim's gear list:JohnFrim's gear list
Sony SLT-A57 Sony DT 18-55mm F3.5-5.6 SAM Sony DT 18-250mm F3.5-6.3 +3 more
Sony SLT-A57
If you believe there are incorrect tags, please send us this post using our feedback form.
Flat view
Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow