Re: Filters for HIE

["Willem-Jan Markerink" <w.j.markerink@xxxxx>]

On  3 Aug 97 at 17:59, J.Wood wrote:

> Several days ago I had an unexpected event, using an 87C gelatin filter
> mounted behind the lens. A triangular piece about the size of a match head
> broke out of it on the bottome side.  Forturnately it was at frame 30.  The
> filter had been used for three rolls of HIE and was not touching the
> film--at least no scratches on film.  I have no idea what caused this.
> Possibly it is related to when I cut the filter to size, using very sharp
> scissors with the filter between two pieces of paper.  I used a new razor
> blade to trim it a small bit so it would fit tightly between the rails. The
> filter may be more brittle that it appears.  Maybe it only accomodates
> three rolls before the material suffers fatigue. Or possibley, it was a
> singular event.  BTW, the exposure worked well with film speed of 100 set
> on a hand held metter and no other corrections made for the filter, but
> developed in D-19 for use on a diffusion enlarger.

I never liked gelatin much, the only gel's I have are a pair of 
#88A's, for the sake of reference. But my dislike is more related to 
the sticky behaviour when touching them with your bare hands....it 
would be a PITA to cut them so precise for this BTFR application. 
In hindsight I also wonder what they do in extreme cold....somehow I 
expect them to become more brittle....
There are better alternatives though; a thin & flexible #87 polyester 
foil of about the same thickness (0.1mm), or a thick & sturdy 
polyester #87C foil (0.4mm), which I currently use in my EOS-1. This 
thick foil is more scratch resistant than the thin version, and I 
have run dozens of films since, including darkloading at the most 
impossible and hectic places. It is a bit harder to cut, but a sharp 
knife should work.
It will depend on your camera design whether you can get away with 
this thickness (it should be less than the height of your film 
rails). The film never touched your gel, did it?
If you are interested in one of these filters send me a private mail.
I might soon have another source of IR-transmissive material, at 
least in 1mm and 2mm thickness....not sure yet whether I can it less 
thick without indulging in an insane minimum quantity order....8-))



- -- 
Bye,

Willem-Jan Markerink


      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]
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