Wratten 87c filter

[Hondo <btl3@xxxxxxxxxxx>]

I have been using a #25 red filter for my IR images with HIE. I have
been using f11 at 1/125th of a sec exposure, and have gotten some great
stuff. I want to get a more opaque filter, like the 87 or 87c. If I get
one, what is a good place to start as far as f-stops and shutter speeds
are concerned? I'm not sure if I'll have to expose longer with this type
of a filter. I could use a little help here.....  thanks!  

Also, if anyone has an extra of this type of filter they would like to
get rid of, let me know! I'm having trouble finding one locally.

Brian
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