kymarto Loc: Portland OR and Milan Italy

I urge people to do their own tests to see how and when and to what degree a filter affects the final image. It is easy in the days of digital to take two identical shots, one with and one without filter, and compare at 100%.

My own series of tests showed me that a filter affected the image noticeably only in the presence of a bright light source shining directly into the lens, and even then only minimally. Because I often shoot in less than ideal conditions outdoors, that was enough to convince me to keep a filter on each lens as normal practice.

I find it odd that people are terrified of cleaning sensors, with their glass surfaces, while being nonchalant about cleaning glass lenses. In the course of 50+ years of shooting, I have seen my filters collect cleaning marks, that would have been on the lenses had I had to clean them from various spatters and wind-borne contaminants. It is true than small scratches on a lens, even many of them, do not really affect a lens' performance, but why risk that if you can prevent them?

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

So, what you are saying is the majority of us (film?) in the desert, or near the sea, or around working machinery, and are around fires, so we need UV filters. REALLY? Your serious? Most of us are around this stuff so we need a UV filter. U are funny.

kymarto Loc: Portland OR and Milan Italy

There is sticky and abrasive stuff in the air everywhere. Glass has a MOHS hardness of 5.5, coatings even less. Silica and quartz have MOHS hardness of 7, and they are major components of dust. Aluminum oxide has a MOHS hardness of 9. Any tiny grain of any material harder than glass is going to cause a scratch if pressure is applied to remove it, even if your tissue is clean.

Normally you can remove dust with air or a brush, but not always if you have any oil or grease on the surface of the lens. Water, unless it is distilled, contain impurities that will be deposited on a surface when the water evaporates. There will be scratches. Many are microscopic and invisible to the naked eye. They will not affect the image --fair enough. But they accumulate over time.

And you have to be extremely careful in cleaning your lens. Ever been out in the field and there is something happening and suddenly you notice spots on the lens? The choice is to carefully clean the lens and miss the shot, or give it a quick wipe now not to miss the opportunity.

If you are an amateur just taking the occasional family photo or you work in a studio maybe a protective filter is overkill, but for me in the field, using a filter that does not affect the image and can take the brunt of any unforeseen contact or condition that arises, to protect lenses that cost multiple thousands of dollars is a no-brainer. YMMV

speters Loc: Grangeville/Idaho

That's right, since they are not there to begin with (because of the UV filter), so one does not need PS to take care of that!

Bipod

;sm24:

Try using a resolution test chart, with and without the filter. Then mix up the photos and
see if you can tell the difference. If you can. you have ESP--because there is no difference.

From the point of view of optical engineering, a UV filter is a near-perfect
optic: zero aberrations and distortion. The least absorption and tinting of any optic
(because it's the thinest). It's a "diffraction limited system"--but with less diffraction
than any camera lens having an aperture diaphram. All you have to contend with is
reflection from the surfaces--which is reduced by coating.

And most of the people reading this are using zoom lenses with 20-33 glass/air surfaces....
nd they wonder why the images aren't contrasty. (Of course, if they only look at them on
LCD/LED monitors, it's impossible to see the difference. On an OLED or a CRT you'd
see it: many zoom lens images look washed out, blacks not really black.)

In photography, what you see is never what you get, so one has to know the limitations
of all equipment, including lenses. MFT charts are a good guide to resolution, but only
test for flare caused by light within the angle-of-view (the low spacial frequency test),
not the sun striking the objective from a high angle.

The ironic thing is that the zoom lens--which is most in need of a lens hood--also is
the most difficult lens to hood. Because the angle-of-view changes with the focal
length, you really need an adjustable hood. It's also the most fragile class of lens,
and expensive, and the short to long ones tend to have the most aberrations and
distortion or any lens except a super-wide.

Sports photographers and photojournalists and people who in wet or dirty conditions
need zoom lenes. But for the rest its just a "lazy lens". "I don't wanna change lenses!"
"My camera's too heavy!" "Why do I have to use a tripod?" Etc., ad nauseum.

Maybe cameras should come with a warning sticker: "The Surgeon General has determined
that photography is difficult and requires a photographer. Deal with it, or find a new hobby
such as collecting baseball cards."

latebloomer Loc: Topeka, KS

Some sacrifice is sometimes necessary to test what makes a difference.

Bipod