You can get a nice DOF calculator free from Digital Light & Color, maker
of Picture Window photo editing software. Go to:
<http://www.dl-c.com>
and click on downloads and then scroll down looking for the DOF
calculator. (there's a lot of other stuff you can download for free as
well if you're so inclined).
If we could put our OM lenses on an E-1 which has a 2X factor we'd need
to use a 25mm lens for the same image magnification we'd expect from a
Zuiko 50mm. I just ran a trial calculation of a 50mm lens set at f/5.6
and focused at 5 feet and using 30 lines/mm as the desired resolution.
I then changed the focal length to 25mm and the resolution to 60
lines/mm. (Remember, we have to magnify this half size image twice as
much in order to get the same size print). The 25mm then shows the same
DOF as the 50mm when it's at f/2.8. In other words, we had to be able
to open up 2 stops to maintain the DOF.
CH would not have as big a jump with his 10D since I think the
magnification factor with that sensor is about 1.6 instead of 2 as it is
with the E-1. Even though it's only two stops difference Oly has a bit
of a challenge to duplicate the shallow DOF effect of the OM Zuiko 85/2
in a 40-50mm 4/3 system E-series Zuiko. Anybody for a 42.5mm f/1.2?
The announced E-1 zooms only go down to 2.8 so they will have DOF
performance like 5.6 on 35mm.
Am I talking myself out of an E-1? Maybe somebody can find a technical
hole in my argument and tell me it's not really two stops.
Chuck Norcutt
Woburn, Massachusetts, USA
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