Darkroom lights for RA4 or Ilfochrome

Rudeofus · Jun 24, 2010

I just recently found a photo club which maintains a nice dark room, so I may be a large step closer to making my own prints. While many posts here mention that color prints are to be made in complete darkness, I vaguely remember that there were special yellow lights to which (at least RA4) photo paper is not sensitive.

Is this correct or just a myth? Can I use these lights for Ilfochrome, too?

hrst · Jun 24, 2010

Very dark yellow with correct wavelength can be used at a very low level. I use just yellow leds at very low level. I can barely see something after a while but it's better than nothing, and I've tested it free of fog up to 5 minutes. I tested it for Ilfochrome and noticed it works as well if not better.

Tom Kershaw · Jun 24, 2010

hrst said:
Very dark yellow with correct wavelength can be used at a very low level. I use just yellow leds at very low level. I can barely see something after a while but it's better than nothing, and I've tested it free of fog up to 5 minutes. I tested it for Ilfochrome and noticed it works as well if not better.

Have you made Ilfochrome prints recently?

Tom

markbarendt · Jun 24, 2010

(there was a url link here which no longer exists)

pentaxuser · Jun 24, 2010

Can't speak about Ilfochrome as I have never made any but sodium lights such as the DUKA 10 and 50 will give quite a good light level without fogging.

I once used a Durst tricolour lamp which had a small incandescent bulb with different filters and the one for colour paper just about allowed me to see a hand waved vigorously in front of my face after about 15 mins. In other words, next to useless.

The sodiums are in a different league

pentaxuser

pentaxuser · Jun 24, 2010

PS I realise I should have added that I was referring to printing RA4 with the sodium DUKAs. Hopefully this is what you will have inferred anyway.

pentaxuser

hrst · Jun 24, 2010

Tom, I tested my safelight for Ilfochrome about 2-3 years ago on a fresh paper. I didn't get any fog at the same level & time when I started see some minor fog on RA-4.

But the only way to know is to test the particular safelight you are using.

thefizz · Jun 28, 2010

I use the colour version of these torches for RA4 printing and find it very handy:
http://www.rhdesigns.co.uk/darkroom/html/safetorch.html

Rudeofus · Jun 30, 2010

First of all: thanks a lot for all the replies! So it basically boils down to using light with a wave length to which photo paper is not very sensitive and keeping the light level low enough. Do people use some special procedures to keep fogging at a minimum? I.e. turn on the light only when absolutely necessary or only between steps?

pentaxuser · Jun 30, 2010

Rudeofus said:
. Do people use some special procedures to keep fogging at a minimum? I.e. turn on the light only when absolutely necessary or only between steps?

Unfortunately you can't do that with a sodium DUKA. The bulb needs time to warm up to the temp at which the wavelength doesn't affect paper so if you use the lamp at a luminance bright enough to really see with then this affects some colour analysers which need to be used in practically complete darkness. Unless you want long delays while the lamp warms up each time then the light has to be eliminated by other means.

There are 2 options. Move a lever on the DUKA which moves a shield over the lamp to almost cut out all the light when using the analyser or place a shield over the outside of the light. You could probably make one to fit the light but the top of the box for 8x10 paper does the trick. It's probably as easy and quick as using the DUKA's lever to operate the internal shield.

pentaxuser

TimmyMac · Jun 30, 2010

Try this:
http://www.dealextreme.com/details.dx/sku.12963

Or if you're REALLY cheap,
http://www.dealextreme.com/details.dx/sku.13460
+
http://www.dealextreme.com/details.dx/sku.13552
Solder those together, break a lightbulb (careful!) and solder it into the bulb socket. Pop a film canister over the end for diffusion and you're good to go.

hrst · Jun 30, 2010

Green is a wrong color.

That yellow is probably much much too intense, so you need to work out a solution to lose 99,99% of its light.

If you are into electronics, even a bit, the easiest way is to pick one standard, old-fashion cheap yellow led. As you select, try to avoid leds with "greenish" and "orangish" tints. As yellow as possible.

Then, use at level you can barely see something after a few minutes in dark.

You can use much higher level when you move the paper from developer to stop. This way I can clearly see the paper and it makes handling it easy.

Rudeofus · Jul 1, 2010

hrst said:
That yellow is probably much much too intense, so you need to work out a solution to lose 99,99% of its light.

If you are into electronics, even a bit, the easiest way is to pick one standard, old-fashion cheap yellow led. As you select, try to avoid leds with "greenish" and "orangish" tints. As yellow as possible.

I happen to have a degree in electronics, so I'm quite familiar with LEDs, soldering and electronic circuitry. Yellow LEDs seem to operate at different wave lengths: 585nm, 589nm, 590nm, 595nm, ... is the sensitivity curve of color paper sufficiently flat that these can be considered equivalent or is there some pronounced optimum wave length?

hrst said:
Then, use at level you can barely see something after a few minutes in dark.

You can use much higher level when you move the paper from developer to stop. This way I can clearly see the paper and it makes handling it easy.

So basically the most critical steps are the time between when the paper leaves its box and when it leaves the developer? So the procedure would be: dim the light to the bare minimum, follow exposure and development procedure until stop bath, than raise yellow light level to more comfortable level for the final dev steps?

@pentaxuser: I know sodium vapour lights well but never intended to use one for this purpose, since LEDs output nearly the same wavelength and can be dimmed much more easily, also high power output or efficiency is not an issue. In the long run I plan on creating a switchable dark room light which outputs red or yellow light alternatively. Circuitry and building steps will be posted here.

hrst · Jul 1, 2010

Around 580 nm would be optimum for Kodak RA-4 paper. For example, see page 7: http://www.kodak.com/global/en/professional/support/techPubs/e4020/e4020.pdf . I don't know about Ilfochrome, though. But, as you can see in the figure, green curve is more dangerous as it gets higher quite quickly, so better to be safe on the red side.

You probably know that LEDs have quite a broad bandwidth, something like 20 - 50 nm. This is the main reason the level must be low enough. Adding Kodak Wratten #13 filter (IIRC) would probably double the safe intensity. And for the same reason, the middle point of 580 nm is probably not the best with bare leds. I just selected some random leds that look yellow to my eye, maybe very little bit orangish, (not greenish!), and found out in fogging tests they give me quite bluish fog so the wavelength was well balanced between the red and green sensitive layers.

Theodore99 · Jul 2, 2010

As per my knowledge.I think you can use this lights.

hrst · Jul 2, 2010

Theodore99 said:
As per my knowledge.I think you can use this lights.

Probably not. The specifications don't say which color the led is, but I'd bet they don't use traditional yellow led in reading light. It's probably white or "warm white", sometimes called "amber" to cause confusion. 1 watt is also huge power for a led for this purpose.

Rudeofus · Jul 2, 2010

Thanks, hrst, for bringing up the issue of LED light spectrum, the differences in spectrum among seemingly similar LEDs are much larger than I ever expected In this web page someone measured various LED devices, and their spectrum spills well into the red and green range of wave lengths. I may be able to get a hold of some filter glass which only transmits the Sodium line - I will try out filtering the LED light and will report whether this improves the luminosity to fogging ratio - once I got everything else up and running .

Darkroom lights for RA4 or Ilfochrome

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