P3D Re: sharp viewing lens?

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

>OK, here's an experiment which might help... if you are looking at a 7
>perf slide, can you sharpen the corners of the image by racking focus?
>Does this then soften focus of the image content in the middle? And if
>you are looking at a 5 or 7 perf slide (preferably an RBT with nice hard
>edges), does the frame of the window appear perfectly square, or do you
>see any bending? Does the window look a bit like a pincushin?
>Eric G.
  
OK, I have tried it.  Yes, a little tweaking of the focus will help
improve the edges and yes, there is a bit of pincushion distortion 
at the edges.  This is far from saying that the image is "not at all 
sharp" (again, we need some point of reference here) and dismissing
the red button as NOT being capable of 7p viewing.  

How much would a pair of flat-field magnifiers that deliver sharp
and unistorted images up to the edge of the 7p viewing area and have
a short focal length (say 45 mm) and good 7p coverage, cost?  There 
must be a reason that no commercial viewer has been produced yet 
with such lenses.  

-- George Themelis


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