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

Started Apr 15, 2014 | Discussions thread
Michel J Veteran Member • Posts: 4,009
A fundamental issue...

First of all, thanks a lot for sharing this!

Now a fundamental issue, not about front filter nor front lens, but concerning the groups of lenses themselves, inside. Few weeks ago I makes some testing with old Minolta lenses and get cottony rendering, mostly called "lenses haze".

In respond to your thread, I am wondering if maybe that is not one of the major concerns for these oldies lenses we like (near 30 years old lenses such as: SH, BC, BBC and so on). Here the question: does a very small amount of powder of dust can penetrate inside and are deposited on both sides of the lenses over time, and can give rise to specific concerns (lenses haze?) due to their potential to accumulate and to the unpredictability of the effects of such accumulation in the long term.

So, do we need to take care of this small amount of dust inside, or mostly these lenses are virtually "maintenance-free" and do not need servicing to remove this tad of deposition for literally decades?

JohnFrim wrote:

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.


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Michel J
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