Re: [Largeformat] Converting a camera to an enlarger

[Dick Streff <ds85035@navix.net>]

From: Dick Streff <ds85035@navix.net>

Re: The heat problems and the use of fans.

I agree that styrofoam probably wouldn't be a good idea in that
environment. It stands a good chance of ending up a melted blob in the
bottom of the enlarger head.

I think with an incandescent source some type of powered ventilation
would almost be necessary. Years ago I needed to enlarge some 8x10 negs
at a newspaper I worked for. We happened to have the chassis of an old
5x7 Elwood enlarger laying around sans the light chamber. We also had an
old 9 bulb contact printer tucked away. I mated them together and got a
decent albeit slow 8x10  enlarger out of them. Fortunately I didn't need
to make very big enlargements (11x14's I think), so this light source
was adequate. But had I needed to go any larger the printing times would
have been prohibitive. Even with only nine bulbs the head arrangement
got quite warm to the touch.

If you look at the design of AA's 8x10 enlarger the incandescent source
does indeed have fan powered ventilation. I think the key to avoiding
vibration problems is to mount the fan remote from the enlarger and
connect them with flexible ducting.

If you are looking for cheap fans that should be more than adequate for
the task, check with Surplus Center or C+H Sales. Either one carries a
variety of different fan assemblies at a reasonable price for tinkerers.

Dick Streff




Frank Filippone wrote:
> 
> From: "Frank Filippone" <red735i@earthlink.net>
> 
> > >However, I have two major problems to solve:
> > >
> > >1. Heat. Especially with the reflector, the glass and the negative
> > >    get very hot with time.
> > >2. Uniformity of illumination. All types of bulbs I've tried so far
> > >    give a quite distinct fall-off towards the edges.
> 
> You would have to build a light/mixing
> > chamber.
> > Something that was coated/painted bright white. I was thinking of
> > using thin
> > sheets of Styrofoam to line the inside of the light chamber, as
> > this would
> > help to diffuse the light even further.
> 
> I don;t like the thought of the fan vibrations,  and the thought of
> styrofoam melting makes me scared of a fire......
> 
> so my suggestion is to use THICK glass mirror material to line the chamber.
> The thickness will act as a heat sink, and the reflector quality of the
> mirror will help to even out hot spots.  Make the box out of plywood.
>  Glue the mirror to the walls using silicone sealer for bathtubs, using the
> plop technique.... a little plop here, a little plop there.  Opal glass is a
> good final diffuser.
> 
> Frank Filippone
> 
>