Archived posting to the Leica Users Group, 2006/11/19

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Subject: [Leica] IR cutoff
From: red735i at earthlink.net (Frank Filippone)
Date: Sun Nov 19 07:35:27 2006

It is the only good, acceptable solution...... 

Current lens filters are made with optically clear ( no color)  glass.  They 
are then coated with a thin layer, which is composed of
and thicknessed to make a filter of required characteristics.  The thickness 
is very thin ( like in the word angstroms).

Multi coating is the application of different filter characteristics on a 
single optical element... Essentially multi coatings.

It is reasonably trivial to put this coating on the cover plate.  Why did 
they not do this?  Kodak must have known the IR
sensitivity, previous cameras have shown the problem, there was an industry 
fix, and Leica should have run tests on the sensor to
find its sensitivity to optical frequencies, and someone should have flagged 
this from previous reports in the technology.  We
certainly will never know why Leica looked askance at the issue.  Maybe it 
was.. Fix it in SW......

Leica made the decision to make the M8 the best resolution sensor it could.  
But somewhere, they forgot or mis-read the market that
purple tinged black is not acceptable.

Stephan Daniel has written a message to M8 users in the Leica Forum.  He 
proposes no fix at this time.  He acknowledges there is an
issue, and commits to an update in 2 weeks.  This is all good.  It is 
responsible.

I wish he had published it here too.... 


Frank Filippone
red735i@earthlink.net 

that sounds like a great idea



> His question to me was why not apply this coating to the glass covering the
> sensor? 


> I have no basis for my assumption that to pull out the existing sensor
> filters and re coat them or apply a new sensor cover with a stronger IR cut
> off would cost too much.
> After all, the solution for Kodak sensors since the beginning has been to
> force buyers into hot mirror filters and this is one of the reasons the
> Kodak professional line of digital cameras has been such a roaring success
> story.
>
> --
> Roy Feldman, photojournalism & editorial photography



In reply to: Message from msadat at gmail.com (mehrdad) ([Leica] IR cutoff)