[Leica] How IR filters affect M8 B&W

[henningw at archiphoto.com (Henning Wulff)]

At 5:02 PM -0500 6/17/08, Lottermoser George wrote:
>What you say makes sense.
>Yet, at the same time, it would seem that being digital data, and 
>with all the manipulation that can be achieved in post processing 
>software, that some of those manipulations could also be achieved in 
>firmware.
>I don't know enough about software/firmware to make any claims in 
>these regards.
>
>Fond regards,
>George
>george@imagist.com
>www.imagist.com
>http://www.imagist.com/blog
>Picture A Week - www.imagist.com/paw_07
>


The basic point is that the spectral information is divided into 
three classes, R, G and B and collected in buckets. After that there 
are only limited means of separating the photons (and translated 
charge values) and their qualities into their smaller divisions, and 
that only by comparing what's in one bucket to what's in the adjacent 
buckets. Software/firmware can do no more. Putting filters in front 
of the lens whether IR cut or red makes the sorting of information by 
software a lot easier, as certain variables get reduced in value.




>On Jun 17, 2008, at 1:34 PM, Henning Wulff wrote:
>
>>>  I'd assume that the firmware setting of whether the IR filter is 
>>>on or off may have an effect on the camera interpolation as well - 
>>>yes? no?
>>>
>>>  Fond regards,
>>>  George
>>>  george@imagist.com
>>>  www.imagist.com
>>>  http://www.imagist.com/blog
>>>  Picture A Week - www.imagist.com/paw_07
>>>
>>
>>  George, the only things that the firmware setting does is 
>>compensate for cyan drift and vignetting. It can't compensate for 
>>spectral responses beyond the usual white balance corrections, ie, 
>>global changes.
>>
>>  So setting the firmware 'incorrectly' will cause vignetting 
>>oddities which will be readily evident for lenses which show 
>>significant vignetting, and slight tonal difference due to spectral 
>>response differences in the corners, again with wide angle lenses, 
>>but not other effects.
>>
>>  Just as too high IR response due to shooting without an IR filter 
>>cannot be corrected completely in post-processing in colour shots, 
>>neither can tonal changes such as Peter has shown be compensated 
>>for in firmware, which is of course a type of post processing.
>>
>>  BTW, I've tried some of the same kind of shots as Peter, and 
>>gotten exactly the same results to my satisfaction. They weren't 
>>really processed for posting, but gave me enough to cause me to 
>>leave the IR blocking filter on unless I really want the 
>>high-red/IR look. You can enhance it substantially by using an 
>>orange, or even red filter.
>>
>>
>>  --   *            Henning J. Wulff
>>    /|\      Wulff Photography & Design
>>   /###\   mailto:henningw@archiphoto.com
>>   |[ ]|     http://www.archiphoto.com
>>
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>
>
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-- 
    *            Henning J. Wulff
   /|\      Wulff Photography & Design
  /###\   mailto:henningw@archiphoto.com
  |[ ]|     http://www.archiphoto.com