[Leica] Re: Full frame problems

[henningw at archiphoto.com (Henning Wulff)]

At 11:41 AM -0400 6/16/06, Lawrence Zeitlin wrote:
>The grazing angle of a 50 mm lens (back focus about 30 mm) is about 
>33 degrees at the corners of the image frame. The Kodak KAI-110000 
>sensor, the one that Leica will probably use, requires an angle no 
>greater than 15 degrees. A strong planoconcave correction plate in 
>contact with the full sized sensor might be the least expensive but 
>it would require considerable design work and would not work 
>optimally with all lenses. The plate would have to deflect light to 
>the vertical by 18 to 20 degrees at the corners decreasing to zero 
>degrees at the center. For lenses shorter than 50 mm, the corner 
>deflection angle would have to be greater, longer lenses would 
>require less deflection. A fixed correction plate would work best 
>for only one focal length. One suggestion was to supply alternate 
>plates for specific lens ranges, another was to use a single plate 
>and correct for light fall off by software, the frame actuator or 
>lens coding triggering the right software mode. An alternative 
>suggestion to the planoconcave correction plate is a fresnel lens 
>with groove artifacts removed by software. The suggestion proposed 
>in a Leica press release was to use individual micro lenses over 
>each of the image wells in the sensor, most probably molded into a 
>single pastic overlay. This is a modification of the fresnel lens 
>method.
>
>Which approach will Leica use? I'm taking bets now.
>
>Larry Z

Since Stefan Daniels said that Leica is going to use microlenses, 
I'll take that bet now. :-)

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