A fault on some EIR slides.

[Jason Revell <jason.revell@xxxxxxxxx>]

A past student has sent me a strip of EIR slides with a  fault on it that I
have not seen before and am looking for further ideas on what might be
causing the problem.  Unfortunatly I am unable to put a image up on the Net
due to copyright and other restrictions (it held by the Tate in London) but
I shal describe it as best I can;

The 35mm slides show a fuzzy/diffused pink/magenta circle in the very center
of each frame, more a VERY strong cast than a bright colour.  The circle is
about 8mm in diameter including about 1.5mm of diffusion around it's edges.
The level of this IR fogging is consistant no matter what exposure is given
to the film and their should be no lens flare or anything like that in the
photo as it is a simple copy of a painting.  They have also retaken the
photo's and the same fault reappeared in exactly the same manor, though I do
not know if they used the same camera body.

I it either has to be happening in the camera (I believe they use Nikon's)
or during processing as the level of fog is not changing and the diameter of
the fog mark is consistant aswell.  

My personnal fealing is that it is a processing fault.  That has been
carried out by Joe's Basement in London and the Tate have had other EIR
rolls processed by them with no problems.  It does however look like a mark
from a IR sensor, but do/could they fog the center of every frame? I have
also been reassured that the sensors were switched off.

Is there a possible in camera reason for this fogging that would effect the
center of every frame? (I do not use Nikon's so have limited knowledge about
their internal workings).

So if any of you can shed any light on idea's for this fault or have
seen/heard of something similiar please let me know.

Jason Revell
jason.revell@xxxxxxxxx
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