Specific brand/types of LED lights to avoid?

I was reminded recently that some white LED lighting works much like fluorescent -- that is, the LED itself is an ultraviolet source, coated with a white phosphor mix to make a visually white light.

For white lighting in a darkroom, this would have the same problem as CFL or long-tube fluorescent lights: afterglow. I've seen CFL lamps that continued to glow visibly (even to eyes with little to no dark adaptation) for minutes after being shut off. This is obviously undesirable for a room in which one may handle high speed film. I've also been told of lamps that "ramp down" instead of shutting off (even to the dim afterglow level) immediately.

The effective alternative, incandescent lamps, are getting harder to obtain (and are actually outlawed for sale in some places, or so I've read). I'd rather use the more energy-efficient lamps that produce less waste heat in any case; I can put 150W equivalent light output in a fixture with a limit of 100W for incandescent bulbs, and the fixture will still remain cooler.

Are there specific brands, models, or types of LED lighting (to fit standard medium base screw sockets, and run on 120V 60Hz) that I need to avoid on the basis of significant afterglow and/or slow shutdown? I don't need dimmable lamps, if that makes a difference; they'll be on a circuit with a simple on-off switch.

I've never seen LED afterglow that lasts for more than a second or so.

There's no LED afterglow. They switch off so fast that Pulse Width Modulation is used to dim them. LED lamps don't require warm up like florescent tubes and you can pick what ever color temperature you like. In my darkroom, I still have an old incandescent bulb and a string of $5 red LED lamps I got on ebay for my safelight. I think if you print color, you might think of daylight balanced LEDs with a high CRI.

For an inspection light I do plan to get a fairly bright daylight white lamp to go in a K-arm or similar. For the overhead lamps, it'll be whatever fits in the fixture (it's no bigger than it has to be for common 60W incandescent bulbs), avoiding afterglow.

But I'm getting a major conflict of information here. This poster says some LED lamps fade down slowly, as well as afterglowing. Pure LED light sources, I agree, can turn on and off rapidly enough that even back in the 1970s, in use as displays, they were multiplexed -- that is, all the segments in an 8-digit 7-segment display would turn on in sequence (if active for the displayed number) and do it rapidly enough to look like constant light unless you moved the display rapidly (more or less like thrashing a hand or ruler in front of an old CRT television). The convern is that white LEDs are often not "pure" LED light sources, and phosphors do afterglow (even those in a CRT television, which needed to be refreshed 30 times a second, would continue to glow dimly for minutes after the TV was powered down).

Expect routine deceptive labeling with any kind of lighting targeted to a consumer end of marketing, or even the budget photographic end. It's hard enough to find anything decent in 5000K. There are some screw-in architectural LED bulbs around $35 apiece that have improved color rendering at 4000K, and that might be nice for display walls. Also check specialty bulb sites like Solux. Nothing is more repugnant and junky than CFL, which is just an interim technology anyway. I need to find something better over the toner tray. But for critical evaluation of color prints I have true color matching lighting in another room. I wouldn't trust any kind of LED lighting for that critical of a task.

I use standard LED lamps in my D3, no issues at all with afterglow, delayed start or turn off, the 75watt equivalent covers 4X5 with out any light fall out in the corners, prints grades 2 graded or with filters in VC without issue. On rare occasion I print grade 4 then I switch back to a standard enlarger bulb. I have several brands that I bought at Lows, GE, and Phillips. For the cost of bulb buy one and see how it works for you.

Some do not turn off immediately, there is some fade. I shot a video but can't upload it.

Do you recall the brand?

@DREW WILEY I'm not asking about color-critical lamps at this time, I'm asking about an overhead, general room light -- it would be turned on for tasks like cleaning, mixing chemicals, changing the lens and negative carrier when switching formats, filling trays, etc. It would be turned off to either safelight, for B&W printing, potentially color safelight (if I determine there is such a thing) for color printing, or total darkness for changing film, handing panchromatic materials, or no-safelight color printing. Safelights, if present, would be independent; inspection lamp would be independent (brighter, selected for better color balance, and not limited in diameter by fixture size as much as those in the overhead).

Just ordinary screw-in tungsten bulbs will do that. Yes, they still exist. For example, drop light bulbs have a low-E exemption as well a far longer lifespan due to heavier filaments. Cree has some screw-in LED bulbs around $35 that will provide around 90 CRI (actual, not BS-rated). But I'm coveting one of those Solux LED light banks that's 4000K, 97 CRI, around $300 for a 4' section. Overkill for the sink room, but ideal where dry print evaluation and mounting are done. The drymount press is enough heat as it is, nice in winter, not in summer.

Paul Howell said:

Do you recall the brand?

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I believe it is a Feit Electric bulb from Costco. I have seen it with PAR recessed ceiling fixture bulbs quite a bit. The ceiling fixtures in my living and dining rooms are on a dimmer and take 15-30 seconds to even light up. Others I have light up and turn off immediately. I use an under-cabinet LED strip I bought from Amazon that works great as an examination light in my darkroom. Nice feature is it turns on and off with a touch switch, easy to do in the darkened setting.

Pieter12 said:

Some do not turn off immediately, there is some fade. I shot a video but can't upload it.

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I am glad that I have seen several people mention a very short afterglow. I recently had a discussion on another forum where the same matter came up and unlike this discussion I don't think anyone else mentioned afterglow. However on my 11W LED bulb there is a clear afterglow for may be a second. It doesn't extinguish instantly as do the old tungsten filament bulbs in my experience unless the very latest ones have now overcome this short afterglow.

However unless I were to instantly take out, say, paper or film almost at the same time as switching the light off I don't the glow is long enough to create problems

pentaxuser

Donald Qualls said:

For an inspection light I do plan to get a fairly bright daylight white lamp to go in a K-arm or similar. For the overhead lamps, it'll be whatever fits in the fixture (it's no bigger than it has to be for common 60W incandescent bulbs), avoiding afterglow.

But I'm getting a major conflict of information here. This poster says some LED lamps fade down slowly, as well as afterglowing. Pure LED light sources, I agree, can turn on and off rapidly enough that even back in the 1970s, in use as displays, they were multiplexed -- that is, all the segments in an 8-digit 7-segment display would turn on in sequence (if active for the displayed number) and do it rapidly enough to look like constant light unless you moved the display rapidly (more or less like thrashing a hand or ruler in front of an old CRT television). The convern is that white LEDs are often not "pure" LED light sources, and phosphors do afterglow (even those in a CRT television, which needed to be refreshed 30 times a second, would continue to glow dimly for minutes after the TV was powered down).

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Take a look here.
https://lamphq.com/led-lights-glow/

But LED is silicon technology and they run on DC, not AC. For bare LEDs to run, it requires a powerful supply to convert AC to DC which may have residual power when the power is shut off. because it’s silicon, you’ll have to keep them cool. If they overheat and burn up.

Now they have LED big screen TVs where each pixel is turned on and off as the screen refreshes. It’s pretty amazing to me. I played with LEDs in the late 70s and early 80s as an electronics hobbyists. They were very expensive and the only color they came in was red.

As posted above, the afterglow is a function of the AC to DC circuitry in the bulbs.

I have par20 floods in my darkroom for task lighting. There is a noticeable afterglow for about 1 sec after turning off power. I wait for 20-30 seconds before opening film canisters or camera backs.

I think the freak out about afterglow is overrated. The default overheads in the room that became my darkroom were CFLs. I poked around the ‘net and found both opinions, that afterglow would fog film and paper and also contradictory statements (it’s the internet, right?). The simplest default for me was to just try the existing lamps. They are still up there because there are no fogging issues. Then I installed a 4’ shop light. No issues there either. I wait a moment before opening something light sensitive and then proceed. But fluorescents are old news, LEDs are going to be way better anyway. But whatever floats your boat.

btaylor said:

I think the freak out about afterglow is overrated.

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It is, at least for general overhead lighting in a darkroom. I've used led bulbs with an afterglow in my darkroom for quite some time. They took a few seconds to turn off completely. It was never a significant problem; just switch off the light and wait a few seconds before taking anything light sensitive out of its packaging.
I haven't come across any led bulbs that had an afterglow that lasted more than a few seconds.

Also, they're cheap enough to buy just a couple and try them out, and get some other ones if you don't like them. The discarded ones can still be used in less critical applications elsewhere in your home.

I have a few LED lamps in a bedroom, it can take 30 seconds to go dark. The LED work lamp in my darkroom takes about 20ms to go dark. I measured it with a photodiode to be sure. It was some brand x product from Home Depot.

Maincoonmaniac is correct, the LEDs in a purpose built enlarger light source can be pulsed on in microseconds. The issue how fast can the power supply be turned on and off. That is why cheap LED lamps have a long after glow.

koraks said:

It is, at least for general overhead lighting in a darkroom. I've used led bulbs with an afterglow in my darkroom for quite some time. They took a few seconds to turn off completely. It was never a significant problem; just switch off the light and wait a few seconds before taking anything light sensitive out of its packaging.
I haven't come across any led bulbs that had an afterglow that lasted more than a few seconds.

Also, they're cheap enough to buy just a couple and try them out, and get some other ones if you don't like them. The discarded ones can still be used in less critical applications elsewhere in your home.

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Are you assessing colour prints under the LED lighting? I'm probably slightly old fashioned in that my darkroom general lighting is provided by 100W incandescents and the small outer entrance space by high quality fluorescent fixtures.

Tom Kershaw said:

Are you assessing colour prints under the LED lighting?

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Most of the time, yes. I purchased led strips of "cool white" (around 5500k, but didn't measure) and taped them to the ceiling. It works ok most of the time, but for more critical prints, I like to bring them into daylight for assessment.