RE: Filter Behind the Mirror - Revisited

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

On 25 Feb 98 at 11:23, Christophe Glaudel wrote:

> []  Hi willem,

> My curently IR devoted equipement is an Olympus OM2. the pressure
> plate is recovered by a full exposed - full developped sheet piece
> of Technical Pan to avoid the patern marks on the film due to the
> lack of anti-halo layer (it was a lot of mail about that last
> month).

> I hope my solution is compatible with yours concerning the fiting.
> So you advise me to fit the filter between the film rails perhaps
> it's less expensive for me than purchase a 7x7 cm sq.

If you mean instead of an ordinary filter in *front* of your lens,
then the least important advantage is price....the fact that you
don't have to block your viewfinder with an opaque filter is much
more important....combined with the comfort of changing lenses
without changing filters. Once you get used to this convenience, you
really wonder how you did without before. Also note that there is
hardly any other way with an SLR, if you want to shoot without a
tripod. I could *never* have made many of the 200mm shots I have on
my homepage, taken on a steep ski slope, nor would I have survived
changing the small internal filters on my Sigma 8mm in a nasty -20C
snow storm. 
A filter between the film rails really takes away the hassle of 
mounting external filters....once you get used to this luxury, you 
never want to be without!

> do you think your solution is compatible with my material. I think
> the dimensions for the filter is about 24.7mm height by 38 or 39
> mm  approx  9,386 sq cm

> do your filter is exactly like 87c transmitting??

Yes, and it is the darkest material I can offer, which is still 
flexible and easy to cut. 
I wish I could find something similar in the lighter #89B and darker
#87B....(other than fragile gelatine)....;-((

> one other problem is the thickness of the Scotch tape. I ' m
> afraid of frictions against the film. 

I used plain & simple clear single-sided 'office tape', and haven't
had any problems since I mounted my filter this way almost 1.5 year
ago, with many films run through. I suspect that the tape will fail
in a few years, as this office tape isn't the most stable stuff,
although that might also be related to UV deterioration (which
doesn't happen inside my camera....I hope....:-))

The only critical specification/size for this project is the height
of your film rails....you need a marking gauge (vernier callipers)
to measure this accurately. In my EOS-1 the rails were 0.5mm tall,
so the filter of 0.4mm plus tape worked fine, no touching or rubbing
whatsoever.

Are there any other Olympus 2 users on this list, with a marking gauge 
handy? (you need the bottom end of the device, that little pin 
sticking out)




- -- 
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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End of Infrared-Digest V0 #415
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