DIY cold(ish) light head.

I am just wondering if it is possible to make a DIY cold light head
by mounting compact flourescent lamps in a white box held above the neg
carrier. They might need a diffuser, but if the box were white and the
tubes far enough above the film plane I suspect it might work.

The only issues I can think of is that some of these lamps start with
a bit of a flicker, that some take a while to get to maximum brightness
and that the spectum might cause issues with multigrade paper.

Any thoughts? Has anyone tried this?


--

http://www.petezilla.co.uk

"Peter Chant" wrote in message
...
I am just wondering if it is possible to make a DIY cold light head
by mounting compact flourescent lamps in a white box held above the neg
carrier. They might need a diffuser, but if the box were white and the
tubes far enough above the film plane I suspect it might work.

The only issues I can think of is that some of these lamps start with
a bit of a flicker, that some take a while to get to maximum brightness
and that the spectum might cause issues with multigrade paper.

Any thoughts? Has anyone tried this?

You might try this link. I'm not sure what is better for B&W, condensor,
diffuse or cold. Perhaps someone can explain the advantages of each. I'm
currently using my condensor but I'm thinking of switching to the dichro and
utilizing the "filter" method for contrast control on VC paper.

http://www.largeformatphotography.in...ic/211868.html

"Peter Chant" wrote

I am just wondering if it is possible to make a DIY cold light head
by mounting compact flourescent lamps in a white box held above the neg
carrier.

Yes, but it is not so easy.

They might need a diffuser

If the 'box' is properly built you will not need a diffuser.

but if the box were white I suspect it might work.

Barium or Titanium dioxide. Kodak makes(made?) a white spray paint
for this purpose.

and the tubes far enough above the film plane

Nope, the light source is to the side and mounted in a pipe/recess. The
light shines on the far wall of the integrating sphere/box, bounces around
and illuminates all the inside surfaces of the box equally (this is theory:
the sphere must be 100% reflective and there can be no holes in the sphere -
like for the light to get in or the light to get out.) In any case, it
works 'Good Enough' (especially with GE light bulbs - and you thought the
letters stood for 'General Electric'.). The light comming from the box is
'spooky' - all you see is light: no shadow or detail - and so it looks sort of
like a hole into the infinite.

If you make one make sure the negative never 'sees' the light source(s).

The output of the sphere is a perfect diffuse source.

Color heads make use the integration with three beams of light (CYM) entering
the
sphere. The light that comes out is a perfect (cough) mixture of the
three entering colors.

The only issues I can think of is that some of these lamps start with
a bit of a flicker, that some take a while to get to maximum brightness

That's a _big_ issue. Fluorescent bulbs make dandy thermometers and it takes
minutes for them to stabilize. It is possible to expose with a florescent (arc)
lightsource, but you need an integrating exposure meter (called just an
'integrator' in the graphic arts industry). The light probe must be
filtered so that the probe's spectral sensitivity matches the papers -
the light spectrum also changes as the lamp warms up.

Aristo cold light heads use a heater to keep the lamp warm even when it is off.

The best solution is leaving the light on all the time (then the lamp
tracks room temperature, and that's GE).

In the case of an integrating sphere you would place the shutter at the tube
where the light enters the sphere.

A better solution is to use a halogen bulb (as used in slide projectors) instead
of a fluorescent. The big draw of a cold-light head is that it is a diffuse
light
source - there is nothing special about it being 'fluorescent.

and that the spectrum might cause issues with multigrade paper.

Yup. You need to have the same polycontrast filters in front of the integrator
probe that you are using to expose the paper. It is easier to have two
light sources (plus maybe a third white source for focusing) for the green and
blue parts of the spectrum.

Any thoughts? Has anyone tried this?

Lots of experience when either 5KW arc lamps or small LEDs are used for
illumination - graphic arts and clinical chemistry.

I have a Beseler 45MX condenser enalrger in the darkroom - I sold the
cold-light D3 Omega. I also have integrators coming out of my ears
down in the basement. That may say something.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

Nicholas O. Lindan wrote:
"Peter Chant" wrote

and the tubes far enough above the film plane

Nope, the light source is to the side and mounted in a pipe/recess. The
light shines on the far wall of the integrating sphere/box, bounces around


How did the Omega head that used a cicular tube work? Was that round tube
off to the side?

I've got an old book with design ideas for enlargers. In the section on
disffusion enlargers IIRC it talks about using two diffusers about 1" apart.

I want to build a 5x7 head myself using a large light fixture. So I'm
curious about all this.

Nick

Peter Chant wrote:
I am just wondering if it is possible to make a DIY cold light head
by mounting compact flourescent lamps in a white box held above the neg
carrier. They might need a diffuser, but if the box were white and the
tubes far enough above the film plane I suspect it might work.

The only issues I can think of is that some of these lamps start with
a bit of a flicker, that some take a while to get to maximum brightness
and that the spectum might cause issues with multigrade paper.

Any thoughts? Has anyone tried this?


Lynn Radeka uses such a system. He uses some of the instant on compact
flourescent bulbs. Check out his website to see if he mentions it. If
not, try asking by email.

-Peter De Smidt

The prices of the emitters are coming down -- you have to be careful about
the heat-sinking. One of the co-venture partners sent me some samples but
I've been too busy with other stuff.



"Nicholas O. Lindan" wrote in message
ink.net...
"Peter Chant" wrote

I am just wondering if it is possible to make a DIY cold light head
by mounting compact flourescent lamps in a white box held above the neg
carrier.

Yes, but it is not so easy.

They might need a diffuser

If the 'box' is properly built you will not need a diffuser.

but if the box were white I suspect it might work.

Barium or Titanium dioxide. Kodak makes(made?) a white spray paint
for this purpose.

and the tubes far enough above the film plane

Nope, the light source is to the side and mounted in a pipe/recess. The
light shines on the far wall of the integrating sphere/box, bounces around
and illuminates all the inside surfaces of the box equally (this is
theory:
the sphere must be 100% reflective and there can be no holes in the
sphere -
like for the light to get in or the light to get out.) In any case, it
works 'Good Enough' (especially with GE light bulbs - and you thought the
letters stood for 'General Electric'.). The light comming from the box is
'spooky' - all you see is light: no shadow or detail - and so it looks
sort of
like a hole into the infinite.

If you make one make sure the negative never 'sees' the light source(s).

The output of the sphere is a perfect diffuse source.

Color heads make use the integration with three beams of light (CYM)
entering
the
sphere. The light that comes out is a perfect (cough) mixture of the
three entering colors.

The only issues I can think of is that some of these lamps start with
a bit of a flicker, that some take a while to get to maximum brightness

That's a _big_ issue. Fluorescent bulbs make dandy thermometers and it
takes
minutes for them to stabilize. It is possible to expose with a florescent
(arc)
lightsource, but you need an integrating exposure meter (called just an
'integrator' in the graphic arts industry). The light probe must be
filtered so that the probe's spectral sensitivity matches the papers -
the light spectrum also changes as the lamp warms up.

Aristo cold light heads use a heater to keep the lamp warm even when it is
off.

The best solution is leaving the light on all the time (then the lamp
tracks room temperature, and that's GE).

In the case of an integrating sphere you would place the shutter at the
tube
where the light enters the sphere.

A better solution is to use a halogen bulb (as used in slide projectors)
instead
of a fluorescent. The big draw of a cold-light head is that it is a
diffuse
light
source - there is nothing special about it being 'fluorescent.

and that the spectrum might cause issues with multigrade paper.

Yup. You need to have the same polycontrast filters in front of the
integrator
probe that you are using to expose the paper. It is easier to have two
light sources (plus maybe a third white source for focusing) for the green
and
blue parts of the spectrum.

Any thoughts? Has anyone tried this?

Lots of experience when either 5KW arc lamps or small LEDs are used for
illumination - graphic arts and clinical chemistry.

I have a Beseler 45MX condenser enalrger in the darkroom - I sold the
cold-light D3 Omega. I also have integrators coming out of my ears
down in the basement. That may say something.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

The Omega used a circular tube that sort of surrounded the film stage, the
head was an oblate sphere-oid (shaped like a Kaiser roll) and the light on
the film was all reflected. The example I played with was not in very good
shape, most of the reflective coating on the head's interior had flaked off.
It didn't flicker-much-and exposure times were quite long so the "surge" was
insignificant in the total exposure.

--
darkroommike

----------
"Nick Zentena" wrote in message
...
Nicholas O. Lindan wrote:
"Peter Chant" wrote

and the tubes far enough above the film plane

Nope, the light source is to the side and mounted in a pipe/recess. The
light shines on the far wall of the integrating sphere/box, bounces
around


How did the Omega head that used a cicular tube work? Was that round
tube
off to the side?

I've got an old book with design ideas for enlargers. In the section
on
disffusion enlargers IIRC it talks about using two diffusers about 1"
apart.

I want to build a 5x7 head myself using a large light fixture. So
I'm
curious about all this.

Nick

"Nick Zentena" wrote

How did the Omega head that used a circular tube work? Was that round tube
off to the side?

AFAIK the round tube was in a round gutter and shone up to illuminate the
underside of the cap. The bright inside surface of the cap was then the
light source the negative saw. The tube never illuminated the
negative directly. I don't remember seeing a diffuser glass, but there may
have been one.

I've got an old book with design ideas for enlargers. In the section on
disffusion enlargers IIRC it talks about using two diffusers about 1" apart.

I had an old (1930's vintage) Federal enlarger that was built that way.
The top diffuser was ground glass and the bottom one was opal.
Very inefficient design. Opal glass only transmits 20-30% and frosted about
50%, so the combination was 10-15%.

A holographic diffuser would be a great a solution: high efficiency and
even diffusion. The catch: a 5x7" sheet may run $300 or so.

I want to build a 5x7 head myself using a large light fixture. So I'm
curious about all this.

I would look at an old Elwood. Parabolic reflector and a diffuser glass
above the negative. I ember someone saying they hot-spotted ...

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

"Nick Zentena" wrote

How did the Omega head that used a circular tube work? Was that round tube
off to the side?

AFAIK the round tube was in a round gutter and shone up to illuminate the
underside of the cap. The bright inside surface of the cap was then the
light source the negative saw. The tube never illuminated the
negative directly. I don't remember seeing a diffuser glass, but there may
have been one.

I've got an old book with design ideas for enlargers. In the section on
disffusion enlargers IIRC it talks about using two diffusers about 1" apart.

I had an old (1930's vintage) Federal enlarger that was built that way.
The top diffuser was ground glass and the bottom one was opal.
Very inefficient design. Opal glass only transmits 20-30% and frosted about
50%, so the combination was 10-15%.

A holographic diffuser would be a great a solution: high efficiency and
even diffusion. The catch: a 5x7" sheet may run $300 or so.

I want to build a 5x7 head myself using a large light fixture. So I'm
curious about all this.

I would look at an old Elwood. Parabolic reflector and a diffuser glass
above the negative. I ember someone saying they hot-spotted ...

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

(Peter Chant) wrote in message ...
I am just wondering if it is possible to make a DIY cold light head
by mounting compact flourescent lamps in a white box held above the neg
carrier. They might need a diffuser, but if the box were white and the
tubes far enough above the film plane I suspect it might work.

The only issues I can think of is that some of these lamps start with
a bit of a flicker, that some take a while to get to maximum brightness
and that the spectum might cause issues with multigrade paper.

Any thoughts? Has anyone tried this?

Why? Condenser is better.