[Leica] IR Filters

[henningw at archiphoto.com (Henning Wulff)]

Willem-Jan Markerink has compiled a lot of info on IR on his website, 
including some spectral response tables:

http://www.a1.nl/phomepag/markerink/irfilter.htm

If you can get past the use of colours, there's a lot of info there.

Again, let me mention the Heliopan filters, which tend to be 
noticeably cheaper than B+W and Hoya for the more exotic stuff. They 
have filters (named according to the starting transmission point, or 
RG numbers according to the Schott glass they use) of 695nm (89B), 
715 (88A), 780 (87), 830 (87C), 850 and 1000nm.

Maxmax has a variety of filters as well, but I don't know what the 
nature of their mounts is and they don't have most of the Leica 
sizes, and they also tend to be more expensive than the Heliopan.


>There are a multiplicity of IR filters available, each with a different
>cutoff wavelength.   A good web site explaining the differences is:
>
>http://maxmax.com/aXRayTechnical.htm
>
>The Hoya numbers are related to the cutoff wavelength, but as you can see
>from the chart at the bottom, the other numbers seem arbitrary (or the
>reason is lost).
>
>Certainly, the longer the cutoff wavelength, the more IR effect you get, and
>the longer the exposure.
>
>Here is an example I took with the Wratten 87 (795 nm), and the Hoya 72 (720
>nm):
>
>720 nm:  http://gallery.leica-users.org/v/rjrose/IR/L1000503-b.jpg.html
>795 nm:  http://gallery.leica-users.org/v/rjrose/IR/L1000372-s.jpg.html
>
>Note that the 795 nm picture has slightly more contrast, the trees are a bit
>lighter, etc.
>
>I paid much less for the Hoya 72, BTW.  I tried gel filters, but I get light
>flare coming from leaks around the filter holder.  I got a 52mm, and use
>step rings to 46mm and 49mm.  You can't use the lens hoods, however.
>
>I reformatted the chart from mammax.com, to be a bit more helpful:
>
>  nm Wratten Hoya  M&K
>  350  18A   
>  620  29   
>  675  70   
>  720  89B   72  
>  735  88   
>  750  88A   
>  780              78
>  795  87   
>  830              93
>  850  87C         95
>  900        90  
>  930  87B   
>  1000 87A  100  1000
>
>
>Kaya PF4 is 780nm
>Kaya PF2 is 830nm
>Kaya PF1 & PF3a is 1000nm
>
>Hoya RM72 is 720nm
>Hoya RM90 is 900nm
>Hoya RM100 is 1000nm
>
>M&K #078  is 780nm
>M&K #093 is 830nm
>M&K #095  is 850nm
>M&K 1000 is 1000nm
>
>Wratten 18A is 350nm
>Wratten 29 is 620nm
>Wratten 70 is 675nm
>Wratten 89B is 720nm
>Wratten 88 is 735nm
>Wratten 88A is 750nm
>Wratten 87 is 795nm
>Wratten 87C is 850nm
>Wratten 87B is 930nm
>Wratten 87A is 1000nm

-- 
    *            Henning J. Wulff
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