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Canon EOS 40D Guide to Digital Photography by David D. Busch

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Dust the FAQs, Ma’am.

Here are some of the most frequently asked questions about sensor dust issues.

Q.I see tiny specks in my viewfinder. Do I have dust on my sensor?
A.If you see sharp, well-defined specks, they are clinging to the underside of your focus screen and not on your sensor. They have absolutely no effect on your photographs, and are merely annoying or distracting.
Q.I can see dust on my mirror. How can I remove it?
A.Like focus-screen dust, any artifacts that have settled on your mirror won’t affect your photos. You can often remove dust on the mirror or focus screen with a bulb air blower, which will loosen it and whisk it away. Stubborn dust on the focus screen can sometimes be gently flicked away with a soft brush designed for ...

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