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> [Original Message] > From: Godfrey DiGiorgi > UV filters can cause problems with AF focusing, corner/edge > sharpness, etc. They tend to increase flare and reduce resolution as > well, even good ones. I've not heard about problems with AF caused by using filters. Can you elaborate on that? I won't get into the debate about increasing flare and reducing resolution. > Here's a very recent thread on DPReview that showed serious degrading > of the FA28-105/3.2-4.5 lens performance when using a Hoya HMC UV > filter: > > http://forums.dpreview.com/forums/read.asp? > forum=1036&message=13954325 I couldn't get the message to come up, but from your comment it seems that only a specific lens/filter combination is at issue. > Prior to 20-some years ago, I was using UV and Skylight filters as > 'protection' on all my lenses. One day I took a UV filter off for > cleaning and forgot to put it back with my Nikkor 35mm f/2 lens ... > My results that day were shockingly better than I recalled from using > that lens, That was more than twenty years ago. Coatings for quality filters and lenses are substantially different these days. This is an outdated example, imo. I doubt that one would see "shockingly better" results when removing a Pentax SMC or B+W MRC filter from a good quality multi-caoted lens these days. One may actually "see" no difference except at very high magnifications or under specific circumstances. > A side effect I noticed having removed all my filters is that my > lenses actually required less cleaning. Most of what I see now is > that they need an occasional dusting with a hand-bulb blower to stay > completely clean. With the filters, a thin film would build up > between the filter and the front surface of the lens about every > three-four weeks, requiring removal and cleaning of both glass surfaces. I've never experienced that problem when using filters, but don't doubt that it can occur. Perhaps I'll take a closer look at a couple of my lenses which have been under the Skylight Protection Program for a few weeks. Usually filters are not used on my lenses. > > Since both modern films and digital sensors are relatively > insensitive to UV light and don't need the filtration, a UV filter > for protection is only warranted when you're going to be shooting in > conditions of flying dirt or water. There are several degrees of UV filtration. The basic UV "protection" filter is, for the most part, as you say, just a way to put a few $$ into the retailer's pocket. However, several companies (Schneider [B+W] and Tiffen come quickly to mind) produce UV filters designed to work at cutting through atmospheric haze, reducing the blue found at the shore and at high altitudes, and through the selective use of their filters, allow the photographer to choose the degree of filtration. In such situations, the > degradation in optical performance is less significant anyway and > protecting the lens becomes a true need, not just a security blanket > to drop another buck or ten into a dealer's pocket. > - Always use a rigid lens hood ... it helps protect the lens and > reduce flare. Agreed 100% > - Always use a caps when you're not using a lens. Agreed > - Don't bother with filters unless you need to filter light, and then > use good filters with antireflective coatings. Agreed, but with the caveat to use only Multi-Coated filters for best results. Some filters are designated as "coated" but really only offer one layer of coating, and are not multi-coated. Some people (not you, of course) get fooled by the terminology. Shel
