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03-01-2014, 02:04 PM   #1
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Front Lens - Smudges, Dirt, Scratches & Cracks

From time to time there are posts about having small fine scratches on the front lens element and what they might do to an image. This guy took an old lens and essentially ended up destroying it, but taking pictures along the way....


03-01-2014, 02:30 PM   #2
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It's interesting alright. Now, where did I put that UV filter....
03-01-2014, 04:02 PM   #3
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Interesting article. Fun, too.
03-01-2014, 04:53 PM   #4
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I have seen this one before but its still interesting.

While its true that you do need quite a lot of dirt and scratches before they have a noticeable effect under normal conditions, the results can be worse under some conditions. For example (and I have not tested all of these - but tempted to!):
* Stopped down a bit (like f11+ for example) is likely to produce worse results - because dirt is not as far away from in focus zone.
* Close focus on a subject - again because dirt is not as far away from in focus zone.
* Wide open + close focus, the effect of dirt / debris may be apparent in bokeh behind the subject. I have actually seen this happen even with relatively small amounts of dirt - especially with bokeh light discs.

As I say I'm tempted to set up a test with an old lens at some point because I'm still curious.

03-01-2014, 08:53 PM   #5
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The f/8 and be there (journalists) have been known to clean the front of a lens with spit and their tie. In the day when journalists wore decent clothes, of course, and Tri-X was the norm.
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