Crappy LEDs, nice safelight

[bernard_L]

Some time ago a coworker gave me a RGB LED strip salvaged from the dumpster. I saw an opportunity to improve the safe lighting of my darkroom, two 15W red tungsten bulbs, overall quite dim, just enough to find one's way around.

I thought RGB opened the possibility of a combined safelight/whitelight in one fixture. But the DC/DVD test showed that the "Red" also emitted some green light. So I ordered a piece of Lee Primary Red 106 sheet filter, and proceeded to integrate the strip in a U-shaped PVC profile for mechanical support. And out of curiosity proceeded to do the Kodak safelight test without the red filter.

https://www.kodak.com/content/products-brochures/Film/KODAK-A-Guide-to-Darkroom-Illumination-K-4.pdf

Next I added the red filter, using the natural curvature that it had acquired during storage and shipping. The slight inward slope of the walls of the U profile also helps keep the filter in place without glue.

Now it's (almost) daylight.

Final note. One needs also to test the red filter that swings under the enlarger lens. The paper receives some exposure from that if one adjusts the placement of the paper before the exposure.

 

[koraks]

But the DC/DVD test showed that the "Red" also emitted some green light.

Yes, a well-known problem. Rubylith or a similar red filter tends to help. I came to the same conclusion years ago when building safelights and LED sources for color enlargers.

I thought RGB opened the possibility of a combined safelight/whitelight in one fixture.

The quality of the 'white' light will be abysmal. I cannot recommend this, not even for B&W print processing. It'll be impossible to get any sort of feeling for the tone of the image. It may work OK-ish if you don't care about hue/tone at all, you don't do toning etc. But even then, I personally find the RGB 'white' light obnoxious and tiresome to work under.

Honestly, you're better off saving these RGB strips for Christmas decorations and use dedicated red and high-CRI white strips for your darkroom. All this isn't expensive anymore and easy to implement. Your eyes will thank you many times over.

 

[BobUK]

"One needs also to test the red filter that swings under the enlarger lens."


Despite doing the full Kodak test for the darkroom safelight about once a year, I have never in my life given the enlarger filter any thought.
Definitely now on my list of things to do.
Thanks for the idea.

 

[Mal Paso]

"One needs also to test the red filter that swings under the enlarger lens."


Despite doing the full Kodak test for the darkroom safelight about once a year, I have never in my life given the enlarger filter any thought.
Definitely now on my list of things to do.
Thanks for the idea.

My red filter is in a drawer above the lens, I have never used it or the red LEDs in the lamp house. I even put the red LEDs on a foot switch. How do you find the red filter useful?

 

[BobUK]

My main use is when burning in, and dodging.
It allows me to position hand held masks and dodging tools accurately. Then using my free hand the enlarger is switched off, the filter swung out of the way, and the enlarger timer started.

 

[Steve Goldstein]

I’m jealous of you red-filter guys. My cold light with an Ariso V54 bulb has no red output at all so I see nothing with a red filter.

 

[Mal Paso]

LOL I think I had to open the lens up and still couldn't see much with the red filter on my 45MCRX 50 years ago and got out of the habit. I put red LEDs in the new diffusion head but confess I haven't tried them. I will have to now.

 

[bernard_L]

The quality of the 'white' light will be abysmal. I cannot recommend this, not even for B&W print processing. It'll be impossible to get any sort of feeling for the tone of the image. It may work OK-ish if you don't care about hue/tone at all, you don't do toning etc. But even then, I personally find the RGB 'white' light obnoxious and tiresome to work under.

Honestly, you're better off saving these RGB strips for Christmas decorations and use dedicated red and high-CRI white strips for your darkroom. All this isn't expensive anymore and easy to implement. Your eyes will thank you many times over.

In the plan that did not materialize, I would not have powered each color at 12V full steam; rather adjust to match, e.g., a halogen incandescent. I assume a better CRI can be achieved in that mode than the "white" LEDs, even if metamerism is possible, at least in principle, with a non-blackbody illuminant.

Regardless, I examine test strips and work prints outside the darkroom, preferably near a window if daylight is available. The darkroom "white" light is just to have more comfortable vision than monochrome red. If I would do color printing (Ciba and RA4 a few times a very long time ago) it would be a different question. Since you are much more invested into color printing, you have a different viewpoint.

 

[bernard_L]

My red filter is in a drawer above the lens, I have never used it or the red LEDs in the lamp house. I even put the red LEDs on a foot switch. How do you find the red filter useful?

Of course the answer --when is red filter useful?-- depends on one's workflow.

• Placement of a test strip relative to image
• I print borderless; I position the paper (onto double-sided adhesive strips) using the red enlarger filter. No need for red filter if an easel is used.
• For some dodging or burn-in, I find it convenient to pre-position the tool (or hand) under red light and start exposure by swinging the red filter out (smoothly to avoid vibration). What BobUK said.

 

[koraks]

I assume a better CRI can be achieved in that mode than the "white" LEDs, even if metamerism is possible, at least in principle, with a non-blackbody illuminant.

No, you'd still have distinct peaks/discontinuous light. You can shift the color balance around by varying the red:blue ratio, but that doesn't make the quality of light any better. You're right that it may not be as critical if you don't use these lights to judge prints, but my experience working under these RGB lights is that it's just uncomfortable/tiring for some reason. I'm not sure why that is; I'm curious to hear how you fare under them.

 

[pentaxuser]

My main use is when burning in, and dodging.
It allows me to position hand held masks and dodging tools accurately. Then using my free hand the enlarger is switched off, the filter swung out of the way, and the enlarger timer started.

That's my use and method as well for the red filter. With the standard red filter on a Durst 605 and leaving the lens on the f stop for printing which gives a good enough for my positioning of a dodging mask I have never noticed any effect on the paper

pentaxuser

 

[Mal Paso]

Good red filter input, Thank You!

I have a 4000K dimable LED reflector flood on a swing arm over the fixer and water bath adjusted for brightness. A 10% exposure reduction from what looks good under the light seems to work.