My guess is that PhaseOne has an IR-filter. I think that "green cast" arises when light passes trough the IR-filter at oblique angles. I guess that this was the major reason for Leica to omit the IR-filter.
Leica has two problems in this area:
1) Short distance between exit pupil and sensor on wide angles, because there is no need for mirror.
2) Leica lenses are intended to be used at large apertures, which I think aggrevates the problem with oblique rays.
When IR-filters are added in front of the lens there will be a "green cast" on the edges. The camera has some firmware change to handle that. That is the probably the reason that the "fix" with external IR-filter needs coded lenses. (This speculation is coming from Sean Reid Reviews.)
My guess is that Leica will redesign the M8 with a sensor with IR-filter, and I guess that it will still be 0.5 mm thick.
Michael, when you were working with the extreme wide angle cameras that employ a PhaseOne digital back (P25 and P39, I believe), you described calibrating the "lens cast" so that Capture One software could remove the cyan fringe that resulted at the edges of the frame. This sure does sound like exactly the problem that was such a surprise to Leica when they underfiltered IR at the sensor.
Am I correct that the big digital backs have no IR filter? The Kodak spec sheet for the 39000 chip makes no mention of it.
How well does "lens cast" removal work? Was there any residual under- or over-"cast" when focussing very near or at very wide apertures? Is there any user control over this or is it completely automatic once set up?
Is there a piece of technology in this that Leica should be picking up?