[Leica] Filter for the M8 B+W 486

[meino at innerside.demon.nl (Meino de Graaf)]

Frank,

I just received the latest LFI. It contained a technical description why 
    no interference filter was used in front of the sensor. Mainly two 
technical problems.
        1) The interference that kills the IR, is based on the layer 
thickness, 
so when light rays hit the filter under an angle, the cutoff frequencies 
will shift, but also due to the nature of the filter, it influences the 
color reproduction.
        2) These filters are like mirrors which is a bad thing to have 
inside 
the camera behind the lens. It causes all kind of stray light bouncing 
inside the camera.

Meino de Graaf



Frank Filippone wrote:
> I have been the prime proponent for a filter coating over the sensor cover 
> for the M8 to fix the IR issue....  Leica has told the
> market to use the 486 filter to fix the issue.....I have done some reading 
> and present a write up from Adorama on the filter.....
> 
> "Description 
> This B+W Interference Filter has a completely colorless glass carrier 
> coated with a number of extremely thin, partially reflecting
> layers with precisely computed thicknesses, similar to MC coating. 
> 
> The B+W Filter 486 does not block by means of absorption, but by 
> interference of the unwanted UV- and IR radiation that is
> repeatedly reflected between these layers. 
> 
> It is especially recommended for CCD applications where digital image 
> sensors have not been fitted with an IR protection filter. 
> This filter is completely clear and it requires no increase in exposure. 
> Its filter factor is 1.  "
> 
> I still have to digest this, but it may actually be not possible to have 
> the absorptive filter coating on the cover plate without
> some form of other problems.,.....
> 
> More to follow.. 
> 
> 
> Frank Filippone
> red735i@earthlink.net 
> 
> 
> 
> 
> 
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