Does UV filter attachment to lens reduces sharpness of images?

[dottore]

Hi Colin,

Thank you for that, you illustrated your points very well. I believe we were approaching it from a bit different perspectives: for me one of the most important function of such filter is simple protection of the lens which is used in harsh environments, as in: salt water spray, heavy fog (industrial and near an ocean), steam generated in industrial environment, sand storm, etc. What follows is that in some situations I simply would prefer not to take the filter of, if I do, I risk damaging the lens. Properties like internal reflections, flare, or distortion are important considerations. Now of course, we are talking about "a piece of glass protecting a lens", as opposed to "UV filter", and the "UV" part becomes irrelevant.

What's your first name? (so I can put it in your profile for you)

For me, flaring/ghosting has only ever come down to two situations - the first when I have direct sunlight hitting the front element of the lens at an obtuse angle, resulting in veiling flare, and the 2nd, more an issue with ghosting from point light sources.

For the first situation, testing would probably reveal a particular brand that would reduce it the most, but I've always felt that the "A" answer was always to just eliminate the light hitting the front element (lens hoods usually do a great job on longer lenses due to them being deep, but WA lenses sometimes don't fare so well). Often all it takes is a hand to just block the light, or in the case of long exposures, sometimes one needs to get a little more creative ...

...

(it was worth it though, although case-in-point, I decided to leave another source of flare in the image in the end)

...

For the 2nd situation, I usually just remove the filter, as no filter will improve things in that circumstance -- and infact, even with the filter removed, one typically still gets ghosting anyway.

[Colin Southern]

Hi Colin,

Thank you for that, you illustrated your points very well. I believe we were approaching it from a bit different perspectives: for me one of the most important function of such filter is simple protection of the lens which is used in harsh environments, as in: salt water spray, heavy fog (industrial and near an ocean), steam generated in industrial environment, sand storm, etc. What follows is that in some situations I simply would prefer not to take the filter of, if I do, I risk damaging the lens. Properties like internal reflections, flare, or distortion are important considerations. Now of course, we are talking about "a piece of glass protecting a lens", as opposed to "UV filter", and the "UV" part becomes irrelevant.

Hi Derek,

No - I think we're the same in that respect.

I'm a big believer in using a UV filter for lens front element protection - and have had it save a couple of lenses. I too just leave it on most of the time (I use Heliopan SH-PMC UV Filters exclusively) -- as a rule, it usually only comes off when other devices go on (Vari-ND filter, Lee adapter etc).

[dottore]

Ah, Heliopan - now I understand why the LensTip spectrophotometer measurements do not strike a chord with you

Hi Derek,

No - I think we're the same in that respect.

I'm a big believer in using a UV filter for lens front element protection - and have had it save a couple of lenses. I too just leave it on most of the time (I use Heliopan SH-PMC UV Filters exclusively) -- as a rule, it usually only comes off when other devices go on (Vari-ND filter, Lee adapter etc).

[Manfred M]

Derek - Lenstips is measuring something that was relevant in the film days (other than the well known issue with the Leica M8; that camera does not use an AA filter). The AA filter on a digital camera has a built in UV / IR filter element and the Bayer array only allows certain wavelengths of light through to the sensor.

If we are using these filters as a protective element; light transmission (linear response across the visible spectrum), flatness of the optical element; accuracy of the mounting in the filter assembly, effectiveness of the anti-reflectance coatings and other characteristics are important. They do not discuss the materials used (brass, aluminum or other materials in the mounts). Other than the amount of visible light that is transmitted, none of test results are meaningful to a digital camera.

There are some other problems with their test methods. The evaluation and interpretation / explanation of the results is flawed (take a good look at the graphs and you will see what I mean). Try to figure out their weighting and scoring methodology and figure out how that is in the least bit meaningful.

Just as an aside, I own filters from a number of companies that they are testing; including Heliopan, B+W, Hoya, Sigma and Tiffen.

[Colin Southern]

Ah, Heliopan - now I understand why the LensTip spectrophotometer measurements do not strike a chord with you

To be honest, no testing really "strikes a chord" with me. In general, all they achieve is self-promotion for their site/magazine whilst misleading the public general into believing that the results have any relevance in real-world photography.

If I had to list - in order of importance - the factors that influence the ultimate quality of a photo, things like photographer technique and lighting would be top of the list - things like post-production skill would be a little way down - things like camera and lens choice would be a little further down again, and things like the spectral response of filter brand A over filter brand B would be so far down the list it would be in a different time zone, and be written in another language.

[Adrian]

I am a little bemused by the filters debates that seem to have raged for years far and wide across the net.

Filters are useful for specific effects, but in general I see little merit in fitting them for "protection" except where there is a clear risk of front element damage that cannot be mitigated simply by taking care. I trust reputable camera manufacturers to manufacture lenses fit for purpose.

[Manfred M]

In general, all they achieve is self-promotion for their site/magazine whilst misleading the public general into believing that the results have any relevance in real-world photography.

I couldn't agree more. In general:

1. Test sites test what is easy to do test, rather something that will be meaningful to real world photographers. I don't shoot in a lab; not many people do;

2. Test sites will often make statements of fact, when in reality they are presenting an opinion that is not backed up in any meaningful way or has data behind it. ;

3. Test sites are not going to say anything bad about a product because their livelihood depends on getting manufacturers and local distributors to supply them things to test. They say something negative, their source dries up and they shut down. That might be the reason we don't see any bad reviews.

4. Manufacturers and distributors play the game too - I'm reasonably certain that they "cherry pick" the equipment that is sent out for testing. I'm also fairly certain that they get a head's up on the test results prior to publication. You get the occasional inkling that this is going on when a test site announces that they are delaying releasing some results because....

I get a laugh when people start quoting "facts" from reviews and other stuff they've picked up on the net without having a clue about what these things really mean.

[loosecanon]

I use my camera and lenses. Fitting a filter may reduce quality a fraction from when a lens is new. After a year - well when a filter gets scratched or damaged it is replaced. To clean it I can remove it and clean in an ultrasonic bath. Niether option is available if no filter is used and the lens is damaged or dirty.
In other words, in the real world, away from the test bench, over time images with a filter will be better than those from a poorly cleaned or scratched lens.
As one example when shooting in wet weather every shot my require removal of water from the front element - I much prefer to be wiping a filter.