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Message: <blockquote data-quote="jwstl" data-source="post: 116032" data-attributes="member: 12977">Indeed. I prefer to take the opinion of someone who knows what he's talking about. Let's see what Nikon guru Thom Hogan had to say about UV filters a few years ago. He refers to film but it's even more true of digital...[FONT=Verdana, Arial, Helvetica, sans-serif]Thom's Maxim #19: Don't put extra glass or plastic in front of your expensive, well designed glass unless you need to.[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]There's a tendency amongst amateur photographers to put UV or Skylight filters on the front of every lens they own. This tendency is encouraged by photo dealers, who, as they ring up your expensive new toy add "and you want a skylight filter to protect that lens, right?"[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]The reason the dealer asks this is simple: it's a way to increase their profit. Mail order outfits such as B&H and Adorama have made it difficult for local dealers to charge list price on lenses (though some still manage). For example, the markup on a 24-85mm AF-S lens is quite small, meaning that the dealer might make only $50 on your purchase. The markup on a $30 filter can be as high as 80%. By selling you that filter, the dealer can make another $24 on the sale, increasing his profit by 50%.[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]So the question is: do you need that filter?[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]First, let's examine why a UV or Skylight filter is usually suggested: it won't change colors, nor does it lower the amount of light that passes through to the film/CCD significantly. While most are made of multicoated glass, the two extra air/glass surfaces will have a slight impact on overall contrast due to refraction. Some dealers will tell you that you need these filters to get proper color at altitude, or in bright conditions, or some other nonsense. But the truth is that film hasn't needed UV filtration for quite some time now--all modern film stocks have virtually no UV sensitivity.[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]So what have you gained by putting a filter in front of your lens? [FONT=Verdana, Arial, Helvetica, sans-serif]Well, the other normally suggested reason is "to protect the front element of your lens from accidental scratching or breakage."[/FONT][/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]I suppose. Small scratches on the front element of most lenses don't actually have much effect on optical performance, though. Indeed, unless the lens is a very wide angle lens, about the only optical effect a small scratch would have is exactly the same one as a filter has: lower contrast. (On wide angle lenses at small apertures, depth of field might be large enough so that you'd see optical degradation due to a scratch or blemish.) And if you're going to bump the lens hard enough to create more than a minor scratch, you're probably hitting it hard enough to bust the filter, and glass scratches glass pretty darn well in such situations, so I don't hold much faith in the "protection from breakage" theory.[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]In short, I don't see much of a reason to put a filter on my lens for protection.Indeed, I've found that lens hoods tend to do a better job at that, anyway.[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]But note what I implied earlier in this discussion: adding a filter to your lens degrades optical performance. A really well made filter won't degrade performance noticeably, but it will degrade. Poorly made or inexpensive filters degrade performance more than well made ones. Every air/glass (or air/plastic) transition in a lens adds reflections, despite multi-coatings and quality materials. Every reflection decreases overall contrast. Some reflections can be insidious in this respect--especially if light is hitting the front filter surface unevenly.[FONT=Verdana, Arial, Helvetica, sans-serif]Thom's Maxim #20: Good filters are expensive.[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]I'm always amused when a student pulls out $10 plastic filters and sticks these on the front of their $1400+ lenses. What's the expectation here? Unless it's some cartoon-like effect, this is an almost certain way to lower the quality of image that your camera can capture.[/FONT]http://bythom.com/filters.htm[/FONT]</blockquote>

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