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Re: [Rollei] OT "burning" something in a slide projector

  From Q.G. de Bakker: 

> .....take a slide projector....hold the slide against the opening
> where the lens has been,

I had the following unpleasant experience while using a 35mm slide
projector as a white light source as an illuminatibg system to copy
slides. I though it would have been a strange idea to keep a 35mm
slide inside the projector for 2 hours. So there was actually nothing
in the slide carrier. I kept the lens in purpose on the projector to
make an image the condensor area (where the beam is most uniform) to a
white diffusor illuminating the slide to be copied (I was a student at
the time, and my professor had just explained us how a "Koehler"
condensor system works so I was happy to put it in practice).

I realized afterwards that I had burned the plastic mount of the lens
(a cheap one) because the projector was in fact designed to operate
with a 24x36 frame limiting the beam within the diameter of the
entrance lens, i.e. in the glass area. The frist plastic retaining
ring was half melted.

So my conclusion is : a 35 mm slide projector fitted with its standard
lens is a good white light source to copy slides, but you should add
either a home-made 24x24 aluminum frame or a crossed 24x36 glassless
frame to actually prevent any light to reach the lens mount.

- -- 
Emmanuel BIGLER