 Elaine S. Robbins |
Skylight Filter?? Okay, one more question...Is it really necessary to have a skylight filter on at all times just to protect the lens? I mean, I appreciate the protection (I'm on a student budget!), but won't this reduce the light coming into my lens and thus force slower shutter/wider aperture? By how much will it do so? Thanks again. Elaine
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Jeff S. Kennedy |
No, of course it isn't necessary but its safer than not having one on. UV filters do not diminish the amount of light reaching your film so there is no concern about adjusting exposure. I have UV filters on all my lenses but I treat them more like lens caps than filters. More often than not I will remove them before I take a shot. The only times I leave them on is when there is dust or water blowing around or when sharp focus isn't my top priority. As far as protecting lenses, a filter will help keep the lens clean but a sturdy lens hood will do more to actually protect it (not to mention reduce flare caused by that silly filter).
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Ken Pang |
Just curious about a comment on sharpness and UV filters, Jeff. I've never really noticed any difference, as long as the Filter is clean. At what size print do you start noticing loss of sharpness from a filter? Thanks,
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Jeff S. Kennedy |
Well, I print sizes up to 30x40. I've never gone to the expense of printing one I've taken with a filter just to see if there is an appreciable lack of sharpness. I generally take off the filter to assure the sharpest shot possible. I have no idea if the difference would be visible it just makes me feel better. That being said, sharpness isn't always the most desireable outcome. For instance when I do portraits I may leave the filter on and even stack other filters on top since most portraits are better with a little softer focus anyway.
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John A. Lind |
The use of Skylight and UV filters is a subject of long-standing controversy. Post a strong stand about the issue on USENET's rec.photo and the flame-fest ensues. (Doesn't matter which side you take.) The following is mostly opinion based on what has worked for me, the films I use, and my flash strobes and lenses. I don't use Skylight filters (a.k.a. 1A or 1B). Never encountered a need for the very slight warming they produce with the slide films I use. With color negative, the print processor can (and will if deemed necessary) do much more filtering for color balancing than the effect a Skylight has. Technically a Skylight has a 1.1X exposure correction factor. It's so little it's not worth worrying about even with slide films. I do use a UV almost all the time. It has no correction factor. With my combination of flash strobes and lenses it knocks down the UV content of the strobe. With most of my lenses outdoors, it knocks down UV haze on distant horizons. Not all distant haze is UV. There are a number of other possible sources, especially near a horizon (humidity, smog and dust). A UV won't fix them, only the UV. Your mileage may vary in both situations. Glass and modern multi-coatings inherently reduce UV content of light passing through them but do not block it entirely. All but one of my lenses are primes. The bulk of them have 7 elements or less. Many modern zooms have twice that many elements or more. More glass means less UV reaches the film. Less glass equals more UV content reaching film and it's why your mileage may vary. Jeff is exactly right that a filter adds one more glass element to a lens and can introduce degradation. I have experienced this from uncoated mediocre optical quality filters in prints as small as 4x6 (a good number of years ago). When this was noticed and confirmed by an experiment I became very finicky about filters in addition to keeping them squeaky clean. After trying several brands my conclusion was B+W and Heliopan consistently make the best ones. IMHO the Hoya "HMC" multi-coated are the next tier down, but still very good, and stumbled across a couple older Vivitar "VMC" multi-coated filters that were in the same class as Hoya's. Haven't experienced noticeable degradation up to 11x17 since then, but haven't pushed 35mm format to its limits as Jeff has with 30x40 prints either. Even with B+W's and Heliopan's it's a trade-off. The filter that baffles me completely is the clear "lens protector" which does absolutely nothing except reduce contrast and become a source of flare; every one I've seen is uncoated. I also agree with Jeff a lens hood will usually provide more protection from accidentally banging the front of a lens into something than a filter will. Also became religious about using lens hoods to keep stray off-axis light off the front lens element. One situation under which the UV always comes off the lens is available light night city-scapes, or any other long timed exposure with relatively strong pinpoints of light. Experienced ghost reflections from front/back filter surfaces once during a 4 second exposure of a night city-scape. A lens hood is always used for them . . . again, to keep stray off-axis light sources off of the front element. -- John
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Jeff S. Kennedy |
"Haven't experienced noticeable degradation up to 11x17 since then, but haven't pushed 35mm format to its limits as Jeff has with 30x40 prints either" - FWIW I haven't pushed 35mm to those limits since the majority of my shooting is done on medium format. Which coincides with my overall sharpness philosophy. I know many MF shooters who figure since they are shooting with a larger piece of film then they can go ahead and use fast film and a bunch of filters. I want the sharpest images I can get so I use the slowest finest grained film I can and the fewest filters I can get away with.
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Kris Haskins |
Thanks,
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