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Old Jul 1, 2005, 5:13 PM   #1
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I recently purchase the Rebel XT with kit the 18-55mm kit lense. I did an experiment testing the quality of a landscape photo at different f-stops. The image contained a foreground and background mountains a few miles away. I shot all the photos on a tripod. The sharpest photo was at F/10 with the focus on infinity, and is was sharp from foreground to background. At F/22 is was not very sharp throughout the photo, especially in the mountains. I am confused as to why this is the case since the larger the DOF the more range i should have? Please let me know if you have any thoughts.


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Old Jul 2, 2005, 2:06 AM   #2
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The APS-C sized sensor on the XT & 20D starts to become diffraction limited below f11, by f22 it's quite noticable.

However you get a greater DOF from the smaller sensor anyway compared to a full-frame sensor or 35mm film, so it's not too bothersome.

You should expect your best performance to be at f8-f11.

If you google "diffraction limitations digital cameras" or something like that you will find a great deal of reading matter.
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Old Jul 2, 2005, 6:02 PM   #3
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Also, the results at the extreme ends of a lens's aperture range tend to be less sharp.
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