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Where to get a lens cleaned?
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<blockquote data-quote="480sparky" data-source="post: 525242" data-attributes="member: 15805"><p>I'm not trying to start an argument...... I'm trying to save you the anguish of ponying up good money to have a lens disassembled, cleaned, reassembled only to find you still have the same problem.</p><p></p><p>If you honestly believe it's dust in the lens, then try this simple experiment. Set the camera on a tripod and aim it at a well-let blank wall. Move the tripod/camera as close to the wall as possible. Focus the lens manually to infinity and stop it all the way down. Take a shot, using whatever ISO and shutter speed you like. Do you still see the spots?</p><p></p><p>Now, use a depth of field calculator for the lens you just used and punch in the focal length, focus distance and aperture. Does it tell you what the minimum focus is? If so, does that minimum focus distance allow the wall to be in focus? If not, you have sensor dust. If the lens, focused at infinity, cannot extend DOF to the wall in front of it, there's absolutely no way it can focus <em>within</em> the lens itself. Honestly, I doubt it ever could. Yes, it is possible that a lens can have a depth of field deep enough that it extends into the lens, but this is rare. If focusing on infinity with the lens cannot get the wall into focus, it's physically impossible for anything closer (even if it's inside the lens) to be in focus.</p><p></p><p>Now on to step two. Remove the lens, and put a different lens on. Use the same aperture you used with your dusty lens and repeat the above process. Do the spots still show up? I got a nickel that says they will, and in the exact same places. That's what dust on the sensor looks like.... the same spots in the same places no matter what lens you use (even if you don't have a lens on the camera).</p></blockquote><p></p>
[QUOTE="480sparky, post: 525242, member: 15805"] I'm not trying to start an argument...... I'm trying to save you the anguish of ponying up good money to have a lens disassembled, cleaned, reassembled only to find you still have the same problem. If you honestly believe it's dust in the lens, then try this simple experiment. Set the camera on a tripod and aim it at a well-let blank wall. Move the tripod/camera as close to the wall as possible. Focus the lens manually to infinity and stop it all the way down. Take a shot, using whatever ISO and shutter speed you like. Do you still see the spots? Now, use a depth of field calculator for the lens you just used and punch in the focal length, focus distance and aperture. Does it tell you what the minimum focus is? If so, does that minimum focus distance allow the wall to be in focus? If not, you have sensor dust. If the lens, focused at infinity, cannot extend DOF to the wall in front of it, there's absolutely no way it can focus [I]within[/I] the lens itself. Honestly, I doubt it ever could. Yes, it is possible that a lens can have a depth of field deep enough that it extends into the lens, but this is rare. If focusing on infinity with the lens cannot get the wall into focus, it's physically impossible for anything closer (even if it's inside the lens) to be in focus. Now on to step two. Remove the lens, and put a different lens on. Use the same aperture you used with your dusty lens and repeat the above process. Do the spots still show up? I got a nickel that says they will, and in the exact same places. That's what dust on the sensor looks like.... the same spots in the same places no matter what lens you use (even if you don't have a lens on the camera). [/QUOTE]
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