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broisman Oct 16, 2002 10:16 AM

DOF and closeup lenses
I have just bought a Minolta 7i and this weekend I set up some tests (Both inside with natural light and outside) to check the DOF. I set the camera lense at 50mm, Aperture Priority, and used all of the aperture settings from 3.5 to 9.5. I didn't find much difference in the DOF. Someone told me I could get a shallower DOF by using closeup lenses. Is this the best way or am I doing something wrong with my camera?

JimHunt Oct 21, 2002 7:34 PM

Depth of field tables for the Dimage 7 series can be found here:

One of the characteristics of digital cameras -- with CCD's smaller than 35mm film -- is a large depth of field. Some praise it and some curse it, but it's just a fact of life.

For smallest depth of field use maximum zoom and widest aperture. A teleconverter will also reduce depth of field, but there aren't any that don't vignette at less than maximum zoom.

Close-up lens won't help unless your subject is... CLOSE UP. I just tested one to make sure. The camera can't focus on distant objects with a close-up lens in place.

broisman Oct 22, 2002 8:24 AM

Thanks for the help but I'm not sure I'm reading the chart correctly. Does this sound right. On the 50mm chart, at 3m and an aperture setting of 5.6 the DOF is between 1.83m and 8.57m.

Thanks again for the help.


JimHunt Oct 22, 2002 7:32 PM

You got it on the first try.

One more depth of field trick. If you want the background to be out of focus, then manually focus so that your subject is at the back edge of the depth of field. It works!

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