T3D Re: Medium format macro needs 2 more stops?

[Stephen Puckett <spuckett@xxxxxxxxxxxx>]

Thanks for the interesting explanations about reduced DOF going
from miniature to MF.  I *thought* that I had experienced this.  

This weekend I tried an experiment about which I invite comments 
from this illustrious company.  I used twinned Zeiss Ikonta 6x6's
to take a stereo picture of some cats at about 5m at sunset.  I was 
using Ektachrome 64 so had the apertures wide open (f/3.5) with 
resulting shallow DOF.  I recalled that I had read somewhere about
a commercial stereo camera that had purposely set the focus on each 
lens differently to extend or enlarge the apparent DOF in the 
resulting stereo image.  I therefore set 1 camera at about 8m and 
the other at about 4m.  Unfortunately I was at the last frame of
the roll so only got 1 shot for my test.  The resulting 2 images 
have shallow DOF's in different places as predicted.  The combined 
stereo image has the apparent (at least to me) DOF enlarged by this 
method.  I can shut 1 eye and the 'illusion' vanishes of the
greater DOF.

I have not seen a discussion of this method/effect on P3D or T3D and
could not spot it in the archives (try searching on 'focus' and I 
get many hits).  Comments?  Are there rules or guidelines to this 
method such as 'Set 1 camera focus to achieve the maximum of the 
desired DOF and the other to the minimum'?  Of course, this 
illusion works for me now but it may not work over time when my 
brain finally gets educated.  I remember a time when I did not 
notice wretched mounting problems  ;-)  Perhaps the best guideline 
here is to avoid it because it will come to haunt me.

Steve Puckett, Portland OR





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