You've got it. Divide focal length and aperture by the crop factor.
If you're using a DOF calculator and not just doing a relative
calculation you also need to divide the circle of confusion (or multiply
desired resolution) by the same factor.
Now then, for your E-1 to equal the angle of view and DOF of your OM
with wide open 50/1.4 all you need is a 25mm f/0.7 Digital Zuiko. :-)
Chuck Norcutt
Andrew Dacey wrote:
> One of the things I'm trying to wrap my head around for the switch to
> digital is how the DoF changes. I know with a smaller sensor you get a
> greater DoF for the same field of view (much like you get a smaller
> DoF with larger formats).
>
> But, I'm wondering how one can quickly figure out what aperture you
> should select to get the equivalent DoF with the smaller sensor?
>
> Most DSLR's have a multiplier of 1.5x, that's awfully close to the
> 1-stop magic number of 1.4 (well okay square root of 2 but you know
> what I mean). Or, with the 4/3 system it's a 2x multiplier. What I'm
> wondering is can you simply assume that to get the same DoF you'd need
> to open up 1 stop for APS sized sensor and 2 stops for 4/3?
>
> For instance, say I have 2 Zuikos (had to keep this on topic somehow),
> a 50/1.4 and a 100/2.8. I could mount the 100/2.8 on an OM and the
> 50/1.4 on an E-1 to get the same FOV. Would the 50 at 1.4 give me the
> same DoF as the 100 at 2.8?
>
> If I'm right, it seems like a nice easy way to quickly figure out what
> the DoF would be if you're used to thinking in 35mm terms. If I'm
> wrong, is there a quick formula to use?
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