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Old Oct 23, 2004, 10:18 AM   #1
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Well i havea 28-135 IS lense, and when i am taking pictures I cannot take them with manual focus because it's never really "Sharp". When I put it on auto focus it works but for example my friends say.. "oh sorry that one's gonna be realy blurry" when they take pics with it, but it isn't really that blurry.

I did bring it riding with me once, and it was in an areana that was between 39 and 50 degrees. Could it be something to do with that??
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Old Oct 23, 2004, 10:51 AM   #2
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Well, I can think of reasons why cold would be good and bad. But neither will cause permanant damage.

When it's cold there is less moisture in the air. The moisture can cause distortions that will make the picture worse (but this normally only effects long telephoto lenses.)

When it's cold there is less heat (obviously.) Heat can distort the air (heat mirages) which will make the picture worse (but again this normally only effects long telephoto lenses.)

When it's cold physical things get smaller... contract. Since a lens is made up of different materials (the lenses vs the housing) they would contract at different rates. This could, I guess, cause some problems with focusing.

But there is a more logical explanation to the problem. Check the Diopter setting on the eye-piece. Make sure it hasn't been turned to a setting for people who's vision is going. I've had that problem on my 10D before, where I'd manually focus the camera but the pictures would all be a little off... turned out I was "focusing" as if I had vision trouble when I didn't have vision trouble.

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Old Oct 23, 2004, 3:37 PM   #3
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I agree about the diopter setting. Many folks that report problems with manual focus usually have the diopter set improperly. An easy check (assuming you trust your auto-focus) is to use a/f on a brightly lit and detailed (contrasty writing or cross-patterns) object. Adjust the diopter dial to slightly blur the writing/object, then turn it back until it reaches its sharpest for your eye. That should match the autofocus and your vision.
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Old Oct 24, 2004, 12:03 AM   #4
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i may sound really dumb.. but where's the diopter?
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Old Oct 24, 2004, 3:42 AM   #5
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Its next to where you look through. There should be a small dial that adjusts the viewfinder focus for each individual. I.e, if you are shortsighted etc.
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Old Oct 24, 2004, 11:27 AM   #6
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I SEEIT !!! thanks! ill try that out



that must have ben it because now it looks crystal clear! Thank you!
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