DIY light source for 10X10" enlarger.

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 vapor,
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.

In article ,
jjs wrote:
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 vapor,
tubes, whatever they are because I just don't plain understand 'em.

A fluorescent light source of some kind -- a "cold light" source -- will
give you the most light for the least power (and heat) unless you really
want to use a *lot* of white LEDs. I'm not sure you can get enough output
from a 10x10 grid of LEDs you assemble yourself to give decent enlarging
times with a 10x10 negative, and I am also skeptical that it will be as
even as you'd get with an array of fluorescent tubes.

--
Thor Lancelot Simon

"The inconsistency is startling, though admittedly, if consistency is to
be abandoned or transcended, there is no problem." - Noam Chomsky

"Thor Lancelot Simon" wrote in message
...

A fluorescent light source of some kind -- a "cold light" source -- will
give you the most light for the least power (and heat) unless you really
want to use a *lot* of white LEDs. I'm not sure you can get enough output
from a 10x10 grid of LEDs you assemble yourself to give decent enlarging
times with a 10x10 negative, and I am also skeptical that it will be as
even as you'd get with an array of fluorescent tubes.

This is great, Thor. I appreciate your input.

Are these flourescent sources in round tubes? Or would it be a line of short
tubes? And I gather that they would be left on all the time and I'd use the
lens shutter, correct?

Thor Lancelot Simon wrote:
A fluorescent light source of some kind -- a "cold light" source -- will
give you the most light for the least power (and heat) unless you really
want to use a *lot* of white LEDs. I'm not sure you can get enough output
from a 10x10 grid of LEDs you assemble yourself to give decent enlarging
times with a 10x10 negative, and I am also skeptical that it will be as
even as you'd get with an array of fluorescent tubes.

Incandescent bulbs are about 2% effiecient, LEDs 30-40% and flourescent
bulbs about 60%. However more accurately a 15 watt flourescent bulb will
replace a 100 watt bulb.

There is a trade off. An incandescent bulb is a continuous spectrum light
source, all the wavelengths of visible light (and some near IR and UV) are
present. A flourescent bulb, even the ones sold as continuous spectrum plant
lights puts out light in specific color bands. LEDs are even worse as far
as spectrum output and white LEDs are very blue.

This makes color printing near impossible without an incandescent bulb
and will affect variable contrast paper and may affect regular paper.

Incandescent lights have a very short on/off time. Flourescent ones
take longer to start and fade more slowly. Therefore they are not
good for short exposures. What a short exposure is, I can't say.

LEDs are praticaly "instant on", but if you wanted 500 watts of incandescent
light, you would need about 250 watts of LED. If you were to use Phillips
high power LEDs, which run about 3 watts, you would need around 80 of them
and some way to sink the 250 watts of heat. I don't know what they cost,
but I expect that it would be an awfully expensive proposition.

Small LEDs like the ones in flashlights are far smaller so you would need
hundreds of them.

I would build a box with regular lamp sockets and some sort of ventilation.
Passive ventilation would be better for less vibration.

I would place some sort of diffuser at the bottom, possibly several
layers of "opal" glass.

You could start with incandescent bulbs. If you run into heat problems,
you could switch to CFLs (screw in compact flourescent lamps) but you
may need some sort of shutter and delay unit. Properly sequenced, fan on
normally, turn off fan, turn on lights, wait 5 seconds, and then open
the shutter. When the exposure time expired, close shutter, turn off
lamps and turn on fan.

As for incandescent bulbs, you may have to find ones with the
lettering on the side instead of the bottom.


Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

On 4/9/2008 9:23 AM jjs spake thus:

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?

Fine ground glass, definitely. Which you can easily make yourself out of
any ordinary window glass. (You know how to do that, right? using
valve-grinding compound, etc.)

I got my old Elwood 5x7 illuminating very sweetly by "tweaking" the
glass diffusers that came with it (it had 3 sheets of glass in a
sandwich). I ended up grinding one of them on both sides, which made a
remarkable difference. "Tuned" it by making blank exposures (no neg) and
checking for consistent gray tone across the field. (Most of the
"tuning" consisted of rotating the light bulb with respect to the
enlarger, so if you use a LED array, you probably won't have to do this.)


--
The best argument against democracy is a five-minute
conversation with the average voter.

- Attributed to Winston Churchill

On 4/9/2008 10:19 AM Geoffrey S. Mendelson spake thus:

As for incandescent bulbs, you may have to find ones with the
lettering on the side instead of the bottom.

There are ways to remove the lettering on the bottom. (Don't ask me how
I know that.)


--
The best argument against democracy is a five-minute
conversation with the average voter.

- Attributed to Winston Churchill

"jjs" wrote in message
m...
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
vapor, 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.



Years agom I had a Solar brand 5x7 enlarger. The lamp head was a huge globe,
possibly 16" in diameter, with a large base incandescent bulb. The globe was
silver inside. There was a pair of diffusion glasses, separated by about one
inch. The top glass had an additional diffusion spot in the center to offset
the hotspot caused by the bulb.

Why not a mixing chamber type system? Seems to me a reflective dome with two
or three lights pointing in would be fairly simple. Plus, heat could be
easier to handle because the bulbs would be 'sort of' outside the dome.

My second choice would be flourescent. I don't know what's available, but
surely someone makes a compact fixture about 12" long. Put several of them
side by side in a reflective chamber and diffuse the output. You would have
to use a shutter, and the color temp _might_ cause a problem with
multi-contrast papers.

And finally, here's an outside the box possiblity: Construct the enlarger so
that the head is stationary and the baseboard moves. Open the head to the
outside world, and use the biggest diffuser available, the sky!

This has been a terrific thread of brainstorming. I've learned a lot and
also got pointers to things to explore further.

In return for the good input (and in the original spirit of Usenet) I will
look into the LED array simply to get a realistic idea of what it would cost
for enough light, what the proper power supply would cost, and try to get
the actual color temp of so-called white LEDs and post back. It will take a
while.

Ventilation for the heat is a good point. I've seen flexible tubes that go
to a high volume, low speed blower mounted far from the object. The idea of
using the sky is really "out of the box" and actually goes back to the
old pre-electric, wet plate era where they did contacts only. (When I get
all ****y about Film-is-Dead posts, I dream of exactly such a setup. No
juice photography.)

Oh - still on Ventilation -- very cool idea about putting lamps inside
separate housings outside the head and pointing them into the mixing area.
Given that this beast is about 1500 pounds and 12' tall already, it sure
doesn't add any significant bulk.(Thinking I could have converted an
Airstream trailer to a camera with as much bulk.)

Finally, I must test the electric shutter on B for a few minutes. It was not
used that way in its original camera, but I have a fused box on the bench
and welding gloves.

Tonight I will try to find time to do tentative drawings of a couple
housings - one for traditional incandescents, and one for the external
lights idea.

Thank you all very much again,

John

"jjs" wrote in message
m...
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 vapor,
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.

--
---
Richard Knoppow
Los Angeles, CA, USA

In article ,
"jjs" wrote:

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 vapor,
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.

The Omega 10x10 that I have a diffused halogen light source is merely a
white interior painted metal box with a fan on one side. Two halogen
tubes about 5-6" long, commonly found at home depot or lowes are on the
top surface, mounted about 3/4 foot apart. The Diffusion panel sits
about 4-6 inches below and is straight through projection of the
internal light. I have printed B&W with no unevenness. The diffusion
panel IS the standard 10x10 panel used in Omega 10x10 enlargers -its
milled with a cone peak in the center which distributes the light evenly.

Omega sells the diffuser for 300.00 My lamp house has a single tray
which I installed optical grade glass into to support the 10 x 10 VC
filters bought from Calumet and made by ILford.


Its a Very Simple design.

--
Reality is a picture perfected and never looking back.