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Old May 31, 2010, 1:47 PM   #1
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Default Aperture vs Image Quality

I am posting the question because I notice I get better IQ at higher
aperture settings with my Olympus E-520 with 70-300 or 40-150 lense.
F 8.0 with my 70-300 gives good sharp results.
So is it best to use Aperture priority or Manual mode for most shots ??

Thanks in advance
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Old May 31, 2010, 3:22 PM   #2
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In general, the maximum aperture isn't usually very sharp, and the lens gets sharper as you stop down. But if you stop down too far then the image starts getting blurry again. At the largest aperture, you're using the complete surface of every optical element, and every flaw (either in design or manufacturing) shows up. As you stop down, you use less of many of the optical elements, so many of the flaws have less of an impact on image quality. But if you stop down too far, then diffraction starts making the image less sharp. With the Olympus E-520, once you stop down past about f/15, the image starts getting softer instead of sharper.

As to the choice between Aperture priority vs. Manual more, that depends on what you're shooting. The aperture directly affects the depth of field as well as the shutter speed and ISO setting. There is no "best" for all situations. If you want the sharpest possible image, a setting just short of f/16 would be sharpest and would have less chromatic aberration, but it would also have a very large depth of field that you might not want. Also, using a small aperture means that you need to make up for the loss of light by using longer shutter speeds (risking motion blur) or by using a higher ISO setting (risking image noise.)

Pick your poison.
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
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