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Author Topic: Dusty Canon 17-85  (Read 1797 times)
conan24
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« on: January 23, 2006, 07:22:05 PM »
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I just got a used Canon 17-85 IS lens for my 20d from the B&H used dept. So excited! However, i have noticed small, but in my humble opinion, significant dust particles under the front lens. They had it graded as a 9+  so naturally i'm a little cranky about the whole thing (though i got a great deal on it).

First question: Is this going to seriously impact my images?

#2: What would be the best way to test if it is messing up the photos?

#3: Is there a way to get it cleaned?

I really like this lens, but if my photos are going to have spots, it's a waste of time.

Any advice?Huh??
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Peter McLennan
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« Reply #1 on: January 23, 2006, 11:09:08 PM »
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Quote from: conan24,Jan 23 2006, 06:22 PM
I just got a used Canon 17-85 IS lens for my 20d from the B&H used dept. So excited! However, i have noticed small, but in my humble opinion, significant dust particles under the front lens. They had it graded as a 9+  so naturally i'm a little cranky about the whole thing (though i got a great deal on it).

First question: Is this going to seriously impact my images?

Probably not ever.



#2: What would be the best way to test if it is messing up the photos?

The dust will be most visible at small apertures (F22) and with a strong, non image-forming light (the sun, usually) hitting the front element.   Go outside in the late afternoon, choose a backlit subject that's smooth toned so you can find spots easily.  Make sure the sun's hitting the front glass (but not in the shot) and expose at F22 or so.  If the dust's gonna show, that's when it will.


#3: Is there a way to get it cleaned?

Probably, but I'd test it first.



I really like this lens, but if my photos are going to have spots, it's a waste of time.

You won't have spots unless the dust is HUGE.   I once was shooting a sawing shot with a wide lens very close to the saw.  Near the end of the shot ( it was motion picture film) I thought "Gee, the image looks a little low in contrast".   When I looked at the lens, I could hardly see glass for sawdust.   It's amazing how much crap you have to have on the front element before you get serious image degradation.

Have fun with your new lens!  

Peter
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