infrared filter for Lee filter holder?

[wildbill]

Let's say I have one of these filters from an ebay seller but it doesn't appear to match the density of my b+w brand 89b filter, this thing is completely opaque to my eye. It's a very thick filter and has a notched edge to fit in the lee holder. No brand name, home made I assume. I'm looking for a exposure times, likely in seconds since I'm shooting sheet film and my exposures with my b+w 89b are 2-4 seconds@22 or iso 3. I plan to do some tests but..........

Anyone out there bought and used this guy's filters with efke infrared film?

 

[Dan Dozer]

Hey Vinnie,

I have never shot infrared before, but the other day in a fit of "what else should I get from Freestyle", I got a box of the Efke IR 820 AURA 4 x 5 film. I also got a LEE IR # 87 filter to use with it. It's pretty much totally opaque and for $26, I thought I would give it a try. I wonder how close it is to this filter that you're talking about here. Note that with this film, Efke says not to use the 87C filter.

I have not had a chance to try it out yet, but when I do, I'll see if I can post something.

Dan

 

[wildbill]

Dan, I have the lee 87 as well and there's a reason why they say not to use it with efke infrared! I won't get into it here but loooooong exposures and thin negs aren't what I want. The problem is this guy is selling filters labeled as something there not. I'd still like to try the filter though.

 

[Q.G.]

Do a search for the cut-off wavelength of the various filters that are available, and see where the sensitivity of the IR film of choice ends, so you don't get a filter that blocks everything except wavelengths the film can't see.

 

[Mike Wilde]

Consider finding a black leader from some e-6 120/220 or 4x5 transparencies, and try using that as an impromptu IR filter before blowig a wad of cash on a bought IR filter.

I understand that these black areas are mostly transparent to IR.

I have been told they were made this way so that the black areas of a slide would be not prone to buckling or melting when projecting chromes.

 

[wildbill]

just to be clear, I'm only looking for exposure results regarding the filter from ebay that I mentioned in my original post. I already have other infrared filters.

 

[Mike Wilde]

Test it by sacrificing a single sheet.

Tape a 21 or 31 step step wedge over the film or slide it in in front of the film if you have a 4x5 wedge. Expoese at a nominal exposure, say f/8 for a period of perhaps 30 seconds on a sunny day.

Process as per usual/manufactureres recommendations thne figure out which patch of the wedge gives the best exposure, and work back to what the correct exosure time without that ND stuck in front of the film.