Re: Horizon 202 / HIE- strange fogging problem

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

On  3 Sep 99 at 9:16, Keith Davison wrote:

> 
> 
> > On 26 Aug 99 at 10:37, Keith Davison wrote:
> > 
> > > When I use Kodak HIE in my Horizon 202 I get a strange pattern of "fogging" 
> > > on the film. 
> > > The "fogging" appears as a stripe of very dark fog starting at the begining of 
> > > the film and running for about 6 Horizon frames, this stripe is located along 
> > > the bottom edge of the film (top edge in the camera), and is very dense near 
> > > the edge, fading to nothing just before the frame edge begins.  This stripe 
> > > also gradually fades in intensity as it runs along the film, disappearing, as I 
> > > have said, by Horizon frame 6.  This "fogging" is very puzzling, I could buy a 
> > > light leak in the Horizon, but why does it only affect the first six frames of 
> > > every film?  To my certain knowledge the last roll of HIE through the Horizon 
> > > was used in very bright sunlight for it's last ten frames, but no light leaks 
> > > appear on that section of the film.  HIE from the same batch, used in my 
> > > conventional 35mm bodies shows no fogging at all.  Colour negative film put 
> > > through the Horizon is also fog free.
> > > I am using a homemade 87C filter, the film is darkloaded, and I process in 
> > > Xtol 1+1. 
> > > This problem does not affect image quality at all, but I am curious as to its 
> > > cause, any ideas?
> > 
> > Quick & dirty guess: 
> > You are using a darkload bag that is not perfectly IR-proof....
> > While this might not show with other bodies, you are fiddling much 
> > longer with the 202 inside that bag (or inside a dark room that seems 
> > dark for those other bodies).
> > 
> > The fogging is very typical for darkload/darkremoval of film and 
> > light hitting the cannister....either visible or IR-only.
> > 
> > Btw, do you process it yourself?
> > If a shop handles the cannisters, even with the film leader
> > retracted inside, in daylight, the effect is almost the same.
> > 
> 
> Nope, I load my bodies in a changing bag in my darkroom, also the fogging 
> pattern (one edge only), is too repeatedly specific for this kind of cause.  I 
> process my own film and for IR, I load my spirals in a changing bag in the 
> darkroom also.

Has that bag been proven to be IR-safe, past *and* present?
Note that it is not uncommon that the inner rubber lining on older 
bags deteriorates....

> My latest best guess is a light leak down the shaft of the take up spool.  
> There is no flange on the upper end of the spool, so any leakage down the 
> shaft would hit the wound edge of the film.  This would explain why only one 
> edge of the first six frames is affected, as the film winds on to the spool the 
> diameter increases, gradually taking later film out of the leak area, the lack 
> of anti-halation coating would cause the gradual fading of the fogging, and 
> this theory also fits the "edge darker" nature of the fogging.  
> Do you know what the light trapping arrangement for the takeup spool shaft 
> is?  Might be worth opening the case up to see if I can improve it.

IMHO, it is absolutely impossible that light leaks along this shaft.
Not only is the fit quite tight, it is also lightly oiled, *and* it 
has a larger diameter knob on top.
Also note that to fog the film this way, light has either to go through the 
film spool opening, or hit the edge of the film outside, right after 
the felt trap....and neither effect can be exclusive to HIE (read: 
IR-specific)....*any* film should be fogged that way, in the exact 
same manner.
Falsification of this theory is quite easy: put the camera in bright 
sunlight, with the rewind-knob pulled upwards.
But I would do a similar test with a film of HIE in your changing 
bag....;-))





--                 
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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