Archived posting to the Leica Users Group, 2001/08/29
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At 6:27 AM +0200 8/29/01, Nathan Wajsman wrote:
>Thanks, Mike! The filter is Heliopan 695, which is the one Maco recommends. I
>had to special order it from Robert White in the UK, nobody seems to stock
>this one. It is less opaque than the 87C filter but stronger than the 89B.
>
>I have also shot some Kodak HIE, but I prefer Maco due to the subtle look you
>mention. Maco seems to lie somewhere in between the weak IR films like Ilford
>SFX or Konica IR and the HIE. It is slower than the HIE, by 1 stop in my use.
According to Heliopan (and Maco) the 695 filter - nominal cutoff at
695nm is equivalent to the 89B. The 87C, or Heliopan 830 isn't
suitable as the sensitivity of the 820 film goes to only - surprise!
- - 820nm nominal. You can get some image, but the effective speed is
well below EI 1. Another filter that works well, and cuts off
essentially all visible light is the 715 (88A). You lose the better
part of a stop with this filter compared with the 695, but it will
let you record only infrared. It is also an ideal filter with HIE,
and keeps the speed up of HIE while giving full IR effect. 715 is not
a good choice with the Konica 750 or especially the Ilford SFX.
With respect to the visual differences between filters, the usual
standard is a fresh gel filter that is intended and sold for
scientific purposes, such as Kodak's. I haven't checked them lately,
but when I had access to test equipment, the Kodak filters were
generally right on the money and others were... elswhere. Especially
glass filters diverged widely. I haven't ever checked Heliopan
filters in this way, so I can't say anything about their accuracy one
way or the other.
- --
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com