Re: DIY light source for 10X10" enlarger.

"jjs" <nobody@[EMAIL PROTECTED]
> wrote in message 
news:R7SdnU6pz7oHcGHanZ2dnUVZ_quhnZ2d@[EMAIL PROTECTED]
> To date I've considered enlarger light sources to be 
> engineering well beyond my feeble capability, but I have 
> used and examined only condenser enlargers such as the 
> Leitz IIa and Omega condenser enlarger, but my task now is 
> to make a diffusion thpe for the 10x10 enlarger.
>
> I want something with No built-in filtration. No fancy 
> color mixing for VC papers. No electronics. No side-lit 
> mixing chambers. Just a straight forward light source and 
> a diffusing layer. I question cold light, mercury va****, 
> tubes, whatever they are because I just don't plain 
> understand 'em.
>
> I can blunder head-first into this project, but this group 
> has some smart people with impressive experience, so I'll 
> put my blunder idea forward.
>
> First, I am limited to ~110V AC power although converting 
> to DC is an option. How about a simple array of 'white' 
> LEDs at the top, pointing down over the typical sheet of 
> plastic translucent material found in home supply places? 
> Or should it be fine ground glass? I am not concerned 
> about the variability of LEDs over time unless they change 
> during the time it takes to get an 8X10 negative-to-print 
> just right - maybe a day or two. The power for the light 
> will be run through a robust power-conditioner once set 
> aside for a big minicomputer. Batteries not included.
>
> So far so good? Corrections would be most welcome. OR just 
> let me blunder and if it goes badly I'll post pictures of 
> the catastrophe.
>
   Cold light lamps are just fluorescent lamps. I think you 
could make a decent source by using an array of tubular 
fluorescents in a metal box with diffusion from plastic 
sheets. The plastic should work because the heat from the 
lamps is relatively low. Diffusing plastic that is nearly as 
good as opal glass is easily available and is both cheaper 
and a better diffuser than ground glass.
   Fluorescent lamps, like all gasseous discharge lamps, 
like to work hot and should be run continuously. Exposures 
should be made by usign a shutter over the lens. This was 
the standard setup for the old Saltzman enlagers which had 
something akin to a Packard shutter mounted on a rod below 
the lens in much the same way as the red filters on some 
enlargers.
   There are fluorescent lamps that can be used with 
variable contrast filters without too much limiting of the 
contrast range.
   My own project, which got put on hold for a while, was to 
make a suitable lamphouse for use with a view camera (Agfa) 
to rig it for enlarging while leaving it intact for use as a 
camera.
   Originally I intended to use a large electronic chassis 
for the light box but new ones are quite expensive. I 
suspect a sheet metal shop could make up a suitable box for 
less, at least worth a check.
    Arist makes a lamp that fits both the Saltzman and 
Elwood enlargers but its quite expensive and I am sure a 
satisfactory home made lamphouse could be made much more 
economically.

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Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]