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#11
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Use of UV filters
"Walter Banks" wrote in message
... I would like to see the pro's and cons of a UV filter or some other "lens protecting" glass on a lens. The small ghosts on very high contrast shots suggests that this is not a good idea. It has to degenerate even normal images. w.. When to use a filter... http://www.fredmiranda.com/forum/topic/685667 Not mine, but a nice picture none the less. -Jim |
#12
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Use of UV filters
"Dave" wrote in message ... mj wrote: You pays your money and you takes your choices. For better than 20 years I serviced both 35mm and most medium format systems. I can say that in a small percentage of all the lenses I have repaired (less then 20%) I have seen "protection" filters break into the front element of the lens scratching it. Hoods generally offer better impact protection. IMO You need very careful to understand the implications of that statistic. As a lens repair person you say you see 20% of lenses where the filter has damaged the lens. I don't dispute that at all. But it does *not* mean that 20% of the lenses which have UV filters suffer such damage. Most people, who damage their filters will do it in a far less catastropic manner. They are likely to put a scratch on the filter, replace the filter and not send the lens for repair. Which is why I said less then 20% of the lenses I have *repaired*. Also, whilst I accept filters can damage the lens if hit sufficiently hard, one would have to question whether the lens would have been damaged anyway without the filter. If a knock is sufficient to damage a filter and smash it into a lens, it must have taken quite a knock - quite possibly enough to have damaged the lens anyway. The result of impact damage is a crap shoot at best. I have seen lenses that fell a foot or two and were wiped out then there are the ones that drop three feet and only bend the filter ring. While most of my 35MM customers used "protective filters" not one of my MF customers did and not all of my MF customers were "professionals". |
#13
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Use of UV filters
On Wed, 10 Sep 2008 00:27:47 GMT, "Ken Hart1" wrote:
: : "Walter Banks" wrote in message : ... : I would like to see the pro's and cons of a UV filter or some other "lens : protecting" glass on a lens. : : The small ghosts on very high contrast shots suggests that this is not a : good idea. It has to degenerate even normal images. : : w.. : : : Every piece of glass in the light path has some effect on the image. : : On the other hand, if something scratches the front of the lens, would you : prefer that scratch on an easily replaceable filter, or an expensive lens. : Yes, I know that good quality filters are expensive, but they would be less : expensive than the lens itself. Laying aside the lens protection issue for a moment ... In the film days we used UV filters to cut through haze. It worked (more or less) because film was sensitive to UV light, which was scattered by water droplets in the air and tended to obscure the image. But what about a digital sensor? Is it sensitive to UV light at all? (It sees only red, green, and blue, right?) And if it isn't, is there any reason to use a UV filter other than for lens protection? Bob |
#14
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Use of UV filters
On Sun, 14 Sep 2008 13:54:57 GMT, JT's Keeper
wrote: : FWIW, I just replaced a UV filter (Hunt's, Melrose, MA.), which is used : primarily for "protection." Never did figure out how the filter : shattered sitting in the camera bag... I assume you've ruled out catastrophic physical contact, such as getting banged by a lens, camera, or flash unit. That leaves stress fracture, one contributor to which could be excessive heat. Did you leave the bag in a hot car, for example? The diameter of a metal ring increases when the ring is heated. If a filter's ring is too tightly glued to the glass, heating it will put the glass in tension, possibly causing it to shatter. The effect might be exacerbated if the filter is on a lens but screwed on crookedly, since that might have already caused stresses in the glass. The Hunt's store in Harvard Square is disappointingly tiny. Is the one in Melrose larger? Unfortunately, it's a bit off the beaten path for me. Is it within walking distance of a commuter rail station? Or if one drives, is there any place to park? Bob |
#15
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That works, assuming a rigid, not rubber hood, for all but lenses in the ultra-wide range, where the petal-shaped hoods offer little or no protection for the very convex front element. Sadly, the more extreme lenses may not accept a front filter.
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