Re: EOS 10s and IR?

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

<from the Canon EOS list, cc to IR list>

On 16 Jan 01 at 1:55, Rafal Walas wrote:

> > Do you know what is the source of the "small problem" with IR film
> > in the EOS 1000 and 1000N series cameras? As far as I know, they
> > have a sprocket film drive. Where does the fogging originate?

As I wrote to the EOS list earlier, I believe only the first 
generation (1000 & 1000F(lash) have a mechanical film sprocket, the 
later models (1000N and 1000FN) have an IR-LED....correct me when I 
am wrong....
 
> Yes I (or rather EOS Magazine) have an answer for you:
> 
> "All EOS models have a pressure plate on the inside of the camera that holds
> the film flat during exposure. The prssure plate used for EOS 1000 series
> models has a rectangular hole in it. This is to accomodate the tiny LEDs
> that Quartz Date versions of the cameras use to print data onto the film.
> The same plate was used in non-Quartz Date models to keep costs down.
> Infrared radiation can pass through thin plastic, such as the back of the
> camera. The hole in the metal plate allows this radiation to reach the film,
> causing a small rectangular area of fogging in the bottom right hand corner
> of the picture. However, you can easily alleviate this problem by:
> - taping a piece small square of aluminium foil on the back of the camera
> over the position of the hole, IR radiation cannot penetrate metal; or
> - composing your photographs carefully so that the small patch of fogging
> can be cropped."
> 
> So now everything seems to be clear. EOS Magazine is really valuable source
> of EOS info.

But obviously not a valuable source of IR info....they just 
reinforced a persisting urban myth, that camerabacks leak IR, either 
because they are made from plastic, or have a film window....
Neither claim has yet ever be substantiated by proof of a specified 
brand and model of camera....while the contrary proof is abundant....

And throwing this myth on one pile with the cut-out rectangles used
in (databack-origin) pressure plates only makes things worse....it's
the lack of IR-reflection through the film, thrown back from the
pressure plate onto the film again, that causes a shadow in this area
(=highlight in final print, since we are talking about negative
film....makes one wonder what the effect is on direct reversal
development).

Anyway, it's not so much this wrong perception, but the lack of
common sense with the cited author, since even the theoretical
falsification is easy, by the fact that no IR film would otherwise
survive long exposures of the camera(back) to the sun.... 


--                 
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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