P3D Re: Differential Focus

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Ray Moxom writes:

>I suggest that Differential Focus has its place in stereo photography. One
>of the top exhibition stereo photographers uses Differential Focus to
>optimise film speed, shutter speed & DOF for many of his action shots. He
>slightly varies the focus of the tele lenses on his twin rig. The results
>are impressive and have taken out many International awards.

Thanks Ray!  I would appreciate some details on this... 

1) who is this top exhibitor (I suspect Allan Griffin), 
2) how exactly does he use differential focusing, 
3) how do you know about it (personal communication or is there 
   something published somewhere?), 
4) expand on this "optimize film speed, shutter speed & DOF", if
   possible,
5) are the results of differential focusing impressive or the overall
   technique of action stereo with twin rigs that has won the awards? 
   (I suspect the later)

>From personal experience, when using longer focal length lenses, focusing
is critical and "differential focusing" (another term for failing to match 
focusing in the two manual lenses? :-)) can drive you crazy and spoil the 
result of an otherwise good stereo picture.  While the effect is not too 
great to be seen in projection (hence awards may come in) it is certainly 
noticeable and disturbing in the viewer.

Thanks!

George Themelis


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