Archived posting to the Leica Users Group, 2006/06/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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