[Leica] Was: R10 news, now: the IR filter

[red735i at earthlink.net (Frank Filippone)]

I understand this argument..... the thickness of the IR coating is in the
order of angstroms....  and at an angle, would be "different" in passband
than at 90 degrees.... so the images at the corners would have some slight
change in passband....... IOW, the colors on the periphery would be
different than in the center.  But it is fixed, and based purely on the
angle of incidence.  Easily corrected, as the 6 bit coding does for Leica
now......

Or... put on a differential coating with different thicknesses.... which I
would believe might be too tough to achieve.

So why the fuss over putting the IR coating on and correcting it using the
coding and algorithms in the camera?.   

And why I still do not accept the story........     still looking to be
convinced......


Frank Filippone
red735i@earthlink.net


The specific thickness of the coating  
optimizes its effect over a small range of wavelengths, e.g IR,  
centered on an exact wavelength at perpendicular incidence. For the  
wavelength of interest, the thickness could be chosen to be optimal  
for perpendicular rays, in order to optimize the effect at the center  
of the image, where the center of visual interest usually lies. It  
could also be chosen to be optimal for slightly angled rays, in order  
to produce a zone of acceptable effect that extends from the center as  
far toward the periphery as possible. A significant deviation from  
this ideal angle increases the wavelength of maximal effect. 



Leica presumably made what it deemed the best of a situation that  
necessitated compromise. We live with it, or not, according to our own  
priorities.

--howard