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Old Jun 5, 2006, 2:04 AM   #1
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I have the Pentax DS dSLR with the stock lense. The stock 18-55mm lense has a 52mm thread. I also have a sigma 28-200mm lense with a 62mm thread. I know you can not step up from 52mm to 62mm, but is it a good idea to go from 62mm to 52mm? Is that too much? Logically you can do it without ventage(sp). But I remember reading somewhere that you should not step down that much because the opening of the outter lense will allow too much light and the camera will get the wrong mettering or something.

Also, a lot of people and websites say that a UV filter is A MUST for every single lense. It is a good way to protect your expensive lense from outdoor elements. I know that it is commond for a UV filter to be attached as a protector lense outside, but do you need/should take the filter off when you are taking picture inside? That is one thing that I never understood. Also do people use a polarizing filter as a walk around filter?
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Old Jun 5, 2006, 2:55 AM   #2
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Regarding the first part, you CAN step up your 52mm lens to use 62mm filter. This is what you should do. I was gonna do this for my 52mm and 62mm Nikon lens, but I decided to buy them separate filters instead.


Regarding the second one, opinion is mixed. Some say you should use UV or skylight filter to protect your lens, while others say you shouldn't or you don't need it. If you use them to protect your lens, then I think it is more important to use it indoors, since it's more confined so you're more likely to bang your lens. Especially on indoor parties. But indoors is also where you will encounter low-level lights that will create lens flare.

I don't use them. I only have three lens and one has a hood for protection (my 70-300, which sticks out more). The only filters I have right now are Circular Polarizer and 3-stop ND filters. They're useful for California's sunny weather, though I don't really use them much right now.

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Old Jun 6, 2006, 8:16 AM   #3
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Yes, you can use a step down ring from a larger filter to a smaller lens filter thread. But I would not suggest it for filters you use a lot. In that case I would just buy the appropriate size.

I have used a protective UV filter on all my lenses for the past 35 years without any problems whatsoever. So I, obviously, recommend it. Just keep it on, indoors and out.

After many years of heavy use, the front element of all my lenses are pristine. If the filter gets too grungy and increasing harder to clean, well, I just toss the filter and buy a new one. The UV filter protects your lens from grunge in the air that will slowly deposit itself onto the lens, not just the bumps and dings. And believe me when I tell you, that the grunge will accumulate much faster than you might imagine. This is the real protection a UV filter affords.

For your lenses, buy a good multicoated UV and you should have no flair problems.

Polarizers are great filters, but not especially useful as a general 'walk around' filter. They are basically a neutral density filter, in that they reduce the amount of light reaching the film/sensor by 1.5 to 2 stops. That is a significant amount of light.

Polarizers are best used under two circumstances:
1: To eliminate reflections off glass, water and other reflective surfaces.
2: To enhance colors, especially in blue sky.

But they really are only used when there is a lot of light available to mitigate the light loss they introduce.
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