[trooper]

I recently got a sigma 10-20... love it! However, when I installed a screw mount UV filter on it, I noticed that when looking across the glass at an oblique angle in bright light, I could see what appeared to be a moire or pressure pattern of distortion about 5-7 mm wide in the center of the filter.This would indicate to me that the filter was touching the front lens element. I spoke to B&H, and they had me send the lens back for exchange. I just received the new lens, and saw the same effect, although smaller, about 3 mm wide. My plan at this point is to take the glass out of a cheap 77 filter, and use the ring as a spacer for the UV filter. I'm only going to use it when conditions require it, as in blowing sand or the like, I'm just wondering if anyone else has seen this on their copy of this or any other lens. I imagine that continued contact between the two surfaces would not be a good thing...

[Lowell Goudge]

I recently got a sigma 10-20... love it! However, when I installed a screw mount UV filter on it, I noticed that when looking across the glass at an oblique angle in bright light, I could see what appeared to be a moire or pressure pattern of distortion about 5-7 mm wide in the center of the filter.This would indicate to me that the filter was touching the front lens element. I spoke to B&H, and they had me send the lens back for exchange. I just received the new lens, and saw the same effect, although smaller, about 3 mm wide. My plan at this point is to take the glass out of a cheap 77 filter, and use the ring as a spacer for the UV filter. I'm only going to use it when conditions require it, as in blowing sand or the like, I'm just wondering if anyone else has seen this on their copy of this or any other lens. I imagine that continued contact between the two surfaces would not be a good thing...

I use a hoya 77mm UV[0] there is no way this touches the element. check your filter, and see if the filter element is set back in the threads or centered in the filter frame

[Peter Zack]

Did you simly try to back the filter off? Unscrew it so it's still attached but further out? Then have a look and see what's happening. Is it possible the filter is poorly machined and the glass in it is larger than the flitler ring? When you screw it on is it a bit tight? It may be that when screwed on the pressure is causing the filter to slightly buckle/warp.

If the filter is really touching the front element, that would really bother me. The UV would do far more damage than good. Use a hood and skip the filter