Depth of Focus question

Started Dec 28, 2002 | Discussions thread
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Phil Arnold Contributing Member • Posts: 934
Depth of Focus question

Has anyone else noticed that there seems to be a great difference in sharpness between shots that are absolutely dead on focused and those that are not quite dead on focused? While the Exx cameras are sometimes criticized for having too much DOF for portrait work, it seems that they really have a very narrow DOF that will produce the sharpness that is required to produce good prints at or above 8" x 10".

When I am successful in achieving absolutely dead on focus, the quality of the resulting prints are far better than I expected to get from a 4MP or 5MP camera. If the focus is not quite dead on, it is difficult to get a sharp enough image for even an 8" x 10" print, no matter how much USM I apply in PS. IMHO this difference is the reason so many of us continue to be frustrated by the large number of "OOF" shots we keep getting.

It may not be that the "OOF" shots are that bad compared to the sharpness we might see if we were shooting film, but that "dead on focused" shots are so great that our "OOF" shots look bad by comparison.

In a discussion of capture devices and Oly's new 4/3 standard posted on
http://www.a-digital-eye.com/Olympus43Q&A.html

an Oly spokesperson said, "Pixel count and pixel pitch/size determine how sharp the lens needs to be. A sensor with pixels in the 6 micron range need a more precise lens than those of the average of 10 microns many 35mm film lenses used today."

Without getting into a debate over the pros and cons of competing capture devices, does this statement give us clues to why the Exx cameras seem to be so difficult to focus? If an extra sharp lens is needed to produce quality images with the CCD's in these cameras, then it would stand to reason that the lens would also have to be focused perfectly to get the quality images.

The following photo illustrates how narrow the DOF really is on my E20. It would have been a nice shot if I had gotten the focus more on the squirrel's face (which is what I was trying to do).

Aperture: F3.2
Shutter: 1/125 second
Focal length: 36.00
Metering mode: Center-weighted average
Exposure mode: Aperture Priority
Speed: ISO 80
Flash: Flash Not Fired
Focusing: Manual
Macro: Off
Zoom: 32 (100%)
Flash mode: No flash
White Balance: 5500K
Red WB Bias: 1.46
Blue WB Bias: 1.48
Sharpness setting: Soft
Contrast setting: Low
Software version: 29-1103
Firmware version: D4029

I would appreciate any comments.

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