Amber LED Safelight Report

I got sick of that sinking feeling when a 40$ incandescent safelight does not light up and it's just after 9PM, so that it's too late to run to the photo store (had to wait for sundown before setting up the darkroom, 'innit?).

I did what the modern eco man does: I got myself LEDs.
This one, in red and in amber: http://www.superbrightleds.com/moreinfo/led-household-bulbs/e27-36-led-globe-bulb/438/

With a 30,000 hours estimated lifetime, I thought that two of each would be sufficient (you never know how long you're gonna spend there...). I got the red since every once in a while I like to play with exotic papers/films and can use the added safety. Plus, looking at the spectrum, I knew it would be 100% safe for any VC paper.

But I took the plunge and got the amber as well. The spectrum peaks at 590nm, though it starts around 550nm. Looking at Ilford MGIV, its spectral sensitivity is mostly gone by 550nm, but not inexistent as well.

I setup the darkroom in the garage and put in the amber. I was printing some MGIV for my contacts, and then it was all graded paper. The safelight was about 4 feet above my trays, in opposite direction from the enlarger.

My first reaction was WOW! It's never been that bright in here. So clear in fact that I was scared it was too bright. So I did a quick safelight test: strip of MGIV directly under the light for five minutes. Some very light fogging. However, since the bulb is more directional than an ordinary frosted bulb, I just made sure the beam pointed away from the developing tray, and everything was fine. I then switched on to graded, and had no issues at all.

The amber was a revelation for me. I'm used to working in a red/orange light, and the spectrum of the amber is so much better on the eyes. It really allows for an improved evaluation of contrast without having to switch on the white lights all the time--with red light, it's a necessity. What's more, since contrasts appear "natural" to the eyes, after an hour or so, I had the impression I was working under white light.

To be safer, I could revise a little my setup by either moving the light away a bit more, or getting a less intense one (I got a 36-LED bulb, but there are also 18-LED ones). But since I have a red one as well, I could just switch lights if I'm doing critical printing on VC paper. Which I am seldom doing, since my favourite fine printing paper is Kentmere Bromide graded paper.

In sum, get a LED safelight. It's cheap, it won't break when you schlep it around in your temporary darkroom boxes, and will not die on you during your lifetime.

Thanks, Michel, for your thread. I have been looking for an E27 LED Bulb, 36 LED, red colour, similar to the one you have shown. However, as I live in Spain, the one I need must be 220 volts. Can somebody recommend a led red, 220 v. for a darkroom?
Thanks,
Henry.

Thanks for the link. These look good!

series connection

Henry,

Get two of them and wire in series, point at the ceiling. Great post, much easier than the LED's I assembled from scratch. I use VC paper so I use red, and there is no effect on the paper. I mean no effect whatsoever even with pre-fogged paper and 10 minutes exposure.

I would be careful with the Amber LEDs. I used a Luxeon Rebel Amber LED (e.g. very high power model). It's supposed to to have a wavelength range of 584-597, yet it fogged the heck out of paper at 5 feet away. These are extremely powerful LEDs though so I think the light level may have been a bit much.

I see the 36 and the 8 LED. I don't see 18 or anything in between.

Should be possible to take the 36 LED ones and put some (mostly) neutral density over them though. Since they shouldn't generate much if any heat, even brown paper should work.

18-LED bulb: Dead Link Removed

Michel Hardy-Vallée said:

18-LED bulb: Dead Link Removed

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Those only in cool white and warm white, no red or amber.

Shouldn't be hard to filter the 36s, or use a couple of the 8s, though.

Ah yes, did not notice the colour limitation.

Just place the 36 further away and you don't need any kind of filtration (remember the inverse square law!).

Actually since the "walls" of my darkroom are black plastic hanging in my basement with black plastic overhead, save for one actual wall which is white, I'll just put it in a directional fixture and aim at the white wall OR, aim at the white posterboard I have taped to one wall and the ceiling plastic now to reflect my incandescent safelight. Should work fine.

The other option is bicycle tail-lights, bought online for about $2 each. They're red LEDs and quite paper-safe. You can run them for a few sessions on a pair of AAAs or wire them up to a 3V plugpack for infinite life.

I just leave a 3-LED one on top of my enlarger head facing upwards at the ceiling for diffusion through the room; two or three bounces are required for light to hit the easel. It's plenty of light - I can read the 6-point text on the keys of my f/stop timer.

There's previous threads on this. Been using superbrightleds.com LED safelights for a few years myself. Zero issues with fogging. I use the red ones, bounced off the ceiling.

When I built my LED safelight I had separate dimmable amber and red luxeon LED; but it turned out that I can have a much brighter red LED and still be safe, so I hardly use the amber anymore.

domaz said:

I would be careful with the Amber LEDs. I used a Luxeon Rebel Amber LED (e.g. very high power model). It's supposed to to have a wavelength range of 584-597, yet it fogged the heck out of paper at 5 feet away. These are extremely powerful LEDs though so I think the light level may have been a bit much.

Click to expand...

As I've posted before, some LEDs do emit wavelengths significantly outside of their rated ranges. That, not overall brightness, is usually the cause of residual paper fogging. And as one would expect, the more powerful the LED, the greater the fogging that occurs.

Try this. Go find an old CD somewhere. Turn on your LED and observe its light as reflected off the recording side of the CD, which acts as a poor man's prism. If you look closely I'm betting you'll see the real cause of your fogging. When I did this using my 635nm red LEDs I noticed small, but very distinct, spikes of blue and blue-green light. That explained the light fogging I was seeing.

After mounting my LEDs under a single sheet of Rubylith the spikes, also as one would expect, disappeared completely. And so did my light fogging. As I've mentioned before, I then performed the pre-flashed paper fogging test (using Ilford MGIV FB/RC) and absolutely could not fog the paper even out to 60 minutes of direct exposure. I stopped the test as being pointless beyond that. Perhaps you could do the same or similar with Amberlith? Or the Roscoe filter described below?

This situation is analogous to the claims that the Thomas Duplex low-pressure sodium safelights fog paper because "they're just too bright." Nonsense. If the frequency range of the safe light being emitted does not overlap the paper's sensitivity range, the paper will not fog when exposed to that light, no matter how bright it is.

But the Duplex, like the LEDs, also emits at frequencies other than the (safe) doublet. These include numerous blues and greens, with one sizable spike just below 570nm.* Instead of using Rubylith, these can almost all be eliminated by filtering through an inexpensive sheet of Roscoe #19 Fire theatrical gel.** I've also done this in my darkroom and have tested a fully open Duplex using Kentmere Bromide graded paper out to 30 minutes with absolutely no detectable fog.

Ken

* See here for an example of a real world line spectrum of an unfiltered low-pressure sodium vapor emission formed through a 1mm slit. (Fourth item down the page, click on the third panel.) Note that everything to the left of that bright orange output (the doublet) is capable of fogging various b&w photo papers. Even though your unaided eyes cannot see them, similar outlying emissions can also occur with some LEDs.

** See here for a graph showing the absorption/transmission characteristics of the Roscoe #19 Fire filter.

I can second that not all red LEDs are safe. Using the CD/prism test, I could see that of the three red LEDs, which I have tried, all have differing amounts of non-red ingredients, green mainly, when refracted this way. My current one is a rather very bright, powerful 4W red LED. Using the Kodak safelight test (http://motion.kodak.com/motion/uplo..._motion_products_filter_K4_Safelight_1106.pdf), I was getting fogging at even a 1 minute exposures to the LED safelight, which was pointed at the ceiling, about 2m away. However, having dimmed it by means of an ND filter made out of an exposed/processed sheet of film (transmission density 1.4), it passes the standard Kodak test and is safe up to a 14 minute exposure. It is still very bright, much more than any other safelight I had before.

I will try a different make, lower wattage red LED bulb, with and without a standard red safelight filter, some time this month.

polyglot said:

The other option is bicycle tail-lights, bought online for about $2 each. They're red LEDs and quite paper-safe. You can run them for a few sessions on a pair of AAAs or wire them up to a 3V plugpack for infinite life.

I just leave a 3-LED one on top of my enlarger head facing upwards at the ceiling for diffusion through the room; two or three bounces are required for light to hit the easel. It's plenty of light - I can read the 6-point text on the keys of my f/stop timer.

Click to expand...

I use the same(tail-light) which have four LEDs that take 2xAAA.

I have to wonder if the "out of spec" wavelength described by Ken may be due to sample-to-sample variations as opposed to design specs.

Good to know about the Roscoe gel for the Thomas Duplex. One sheet will easily do both filters.

mgb74 said:

I have to wonder if the "out of spec" wavelength described by Ken may be due to sample-to-sample variations as opposed to design specs.

Good to know about the Roscoe gel for the Thomas Duplex. One sheet will easily do both filters.

Click to expand...

No, LED wavelengths are a function of the chemistry used; you get one wavelength for each electron bandgap in the semiconductors used. You can get variations in relative intensity of the different wavelengths between batches due to varying mixtures of dopants, but the presence or lack of a particular wavelength is all down to the chosen dopants.

Different brands will have different selections of wavelengths (chosen from a handful of basic chemical options); if one LED from a brand has a bunch of parasitic emissions then all of them will. Likewise for a monochrome LED, all the LEDs of that design will be monochrome.

White LEDs are an exception as they are based on a phosphor excited by an UV LED, so they have a weirder spectrum that's much more subject to tweaking and variation.

The most effective contemporary white LEDs are actually based on blue InGaN (indium gallium nitride) LEDs (usually epitaxial layer on top of the SiC substrate), rather than UV LEDs. but that's bit irrelevant to the topic, sorry...

A better safelight filter test

LED's are wonderful safelights. Simply exposing the paper to the LED radiation for a period of time is not a sufficient test. If you want to be sure the safelight isn't going to degrade your prints you need to conduct a test with paper that you have pre-exposed. By pre-exposing the paper the safelight exposure is on the lower portion of straight-line portion of the D LogE curve ( i.e. Zone III) . In practice fogging increases in these densities BEFORE it increases the true D min.


Thius is described in:

http://www.kodak.com/global/en/consumer/products/techInfo/k4/k4TestSafelite.shtml



Bob Shanebrook
makingKODAKfilm.com

Well here's what I can tell you. The red led bulbs from superbrightleds have no fogging issues with any paper I use (ilford, emaks, adox, foma, slavich). If they do I haven't noticed it.

In addition to fog you might always want to check and make sure you don't have any changes in gradation if you're using VC paper. As I recently learned an unsafe safelight will change the grade before it causes any visible fog!

Rafal Lukawiecki said:

.......I will try a different make, lower wattage red LED bulb, with and without a standard red safelight filter, some time this month.

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I read somewhere, and I'm sorry I don't remember where, that the wavelength spread of a "monochrome" LED is narrower at lower currents. I'm not able to test it. I have resorted to very red LEDs which I can use at quite a high level without fogging or other effects. I have made several safelights that were not very safe (less extreme red, and also orange).

I have made a hand-held light with amber LEDs which I use for brief amounts of time when I want better judgement of density, such as preliminary test strips.

For a darkroom 'flashlight" for finding things and such I use my adjustable brightness red LED flashlight I bought and use for astronomy. It does great double duty in the black and white darkroom, and they're cheap:

http://www.telescope.com/Orion-RedBeam-II-LED-Flashlight/p/5755.uts

You can get cheaper ones but they generally don't have adjustable brightness and the bright is pretty darned bright. This one goes down to "dim enough" for astronomy at a dark site, which is dimmer than you need in the darkroom. I could read a book easily on the bright setting once eyes are dark adapted (assuming black print on white - red messes heavily with color vision.)

Amber and RA4

I just pulled an all-nighter printing RA4 (took months of preparation just to make sure every material was on hand!), and I took the opportunity to test my SuperBrightLED Amber light as a colour safelight.

The bad news is: it fogs paper. The good news is: just a bit. The light happens to be around the vicinity of the spectral sensitivity hole, so all it gave was a light cyan cast. The way I used the light was to put it in an adjacent locker, leave the door ajar, and work with the indirect light. It seems it was already too much, but not by terribly much.

I suppose with the weakest LED available, one could put together a safelight that could be useful for quick checks, such as finding your way from the enlarger to the developing tray.

Still, a safelight is not terribly useful for RA4, since you can pretty much turn on the light once the paper is in the stop or the bleach-fix bath if you process in trays; if you process in tubes, then you don't need a safelight, unless you're really clumsy at assembling the tube.