Archived posting to the Leica Users Group, 2001/08/01
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At 9:57 PM -0400 7/31/01, George Kenney wrote:
>Thanks much, Marty.
>
>I had this discussion this evening with my photo workshop
>instructor, who was unfamiliar with the effects of an 87C (because
>he works with SLR in 35 and 120). He tried to steer me to a 25A
>filter, but I pointed out that with a rangefinder the blackness of an
>87C is not an issue.
>
>Anywho, thanks for your constructive comments.
>
>G.
>
>On 1 Aug 2001, at 10:11, Marty Deveney wrote:
>
>> For all the IR info you'll ever need refer to:
>>
>> http://www.a1.nl/phomepag/markerink/mainpage.htm
>>
>> Note that you can buy 120 / 220 Kodak infrared cut down from 70mm
>> aerial stock: http://www.homestead.com/infrared/
>>
>> None of the other medium format films are as sensitive to IR light as
>> Kodak IR film.
>>
>> Also note that the 87-series filters are opaque and MUCh darker than
>> the red filters. Rangefinders are perfect for working with IR film
>> and an 87 series filter because you can see and shoot at the same
>> time. Much better than composing, putting the filter on, locking the
>> mirror up . . . yawn . . .
>>
>> Marty
>>
>>
Using an 87c, even with HIE, is kind of pushing it. The exposure
times are extremely long, and the effect is quite similiar to the 87.
The 87c has only 3% trasmittance at 800nm, while the 87 has 57%. As
the 87 is essentially opaque below 750nm, it is probably the best
choice for HIE. The other commonly available IR films will not work
with the 87c at all, as their sensitivity in not far enough into the
IR. The 87 will work with the Maco, but the 89b is probably the best
one. The Konica will work with the 89b as well, although I like the
results with the 70 best. The 70 has a cutoff at about 660nm, the 89b
at about 690nm, while the 29's cutoff is at 610 and the 25's at 590,
all at approximately 5% diffuse density.
If you want to get just one IR filter, the 89b is probably the most
useful. If you will only be using HIE, the 87 is probably the best
bet. The 87c is mostly useful for experimentation, and stay away from
the 87a (cutoff above 900nm).
Regarding a previous question about loading HIE in the dark, YES,
keep it dim...., very dim. Tech Pan can be loaded in all but
sunlight, but HIE can fog with a 40w bulb in a fairly large room.
- --
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com