High power LEDs

Robert Hall · Apr 13, 2006

Any one know of a good source for large high output LEDs?

I would like to make some safe lights for the darkroom.

TIA

Jerry Thirsty · Apr 13, 2006

I've thought about giving these (the red one) a shot, if my current bulbs ever get around to dying.

Dead Link Removed

No idea how narrow the bandwidth really is. Some of the papers I'm trying require red, but for other people maybe the amber ones would work too?

If you give them a shot, let us know how it goes, please.

Jeremy · Apr 13, 2006

I use these in my darkroom and haven't had any problems with Forte or Ilford paper fogging (10 minute test). They are very bright and one bar of lights was enough for me. Robert, I stll have another bar I can send you if you'd like to give it a shot (and see how bright they are).

I soldered mine (with some heatshrink tubing on the outside) to a variable output power supply from Radio Shack and run them at 9v just to be on the safe side (12v just seems SO bright!).

edit: I have some from the same place Lee Gebhardt bought his from. If you search Apug there is a post or two about this.

ras351 · Apr 13, 2006

Any electronics shop should have leds suitable for your use. Ignore the 15mcd variants but anything between 500mcd and perhaps 2000mcd will be useable. I don't recommend the luxeon style leds as they'll be too bright. As previously mentioned the ones used for show replacement in cars work well but you'll have to reduce the voltage to lower the current and hence light output unless you have a big darkroom. Maybe buy a few different single ones to try - they're at most only a dollar or thereabouts each and in a darkened room they're bright enough.

Roger.

Bob F. · Apr 13, 2006

I use the Luxeon LED. You'll only need the one - as Roger says, they are *bright*. A simple power MOSFET, 3 resistors and a potentiometer cct will provide a continuous dimmer control, or just use one current limiting resistor and make a shade to adjust the brightness. I made mine so I can plug in external LED heads, but that's probably overkill (and after 6 months, I still haven't gotten around to actually making a remote head - I just plug the LED soldered onto a DC power plug into the remote socket)...

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

Cheers, Bob.

jeroldharter · Apr 13, 2006

I bought a couple of the red LED bulbs for sale on the APUG classifieds just to check them out. I have not officially tsted them yet for fogging but no apparent problems. They are very bright and only cost about $15 each.

Papa Tango · Apr 13, 2006

Slightly different use

Has anyone used these led's to replace the bulb in a conventional condenser head? I am thinking that this might be practical. Any thoughts?

lamda · Apr 14, 2006

I have not tried. I've heard the shape of the bulb may be critical to getting even illumination, and the shape of the LED bulb would surely be different from what the enlarger was designed for. Also, incandesent bulbs have a continuous light spectrum, so small dips and bumps in the spectral curves of multigrade papers or multigrade filters won't matter too much. On the other hand LEDs only have a few narrow lines in their color spectrum; if these spots happen to land on a "bad spot" of the spectrum of the filter or paper, it could be hard to get the contrast you want.

resummerfield · Apr 14, 2006

A LED light shouce for VC papers is a proven concept. See this APUG (there was a url link here which no longer exists). A dimming control would be required for these screw-based LEDs.

RJS · Apr 14, 2006

I think Paul Butzi mentioned an LED safelight on his web site. I tried to find the maker and couldn't. Maybe you'll have better luck. It sounded terrific!

Jon King · Apr 14, 2006

Pragmatist said:
Has anyone used these led's to replace the bulb in a conventional condenser head? I am thinking that this might be practical. Any thoughts?

A project of mine, stalled for a good bit, is to make a 5x7 LED head for a Durst 138 using Luxeon LEDs (lumileds). I've built a basic one to test the concept, and it works quite well. I'm using green and blue ones for a VC head with a few red to add light for focusing. Seperate green and blue LEDs are more efficient than using white, especially for green light, and the filtering can be done with the controller, rather than filters

MurrayMinchin · Apr 14, 2006

Jon King said:
A project of mine, stalled for a good bit, is to make a 5x7 LED head for a Durst 138 using Luxeon LEDs (lumileds).

Did you use Blue or Royal Blue, and what grade would you estimate they gave you in contrast? I hear getting a soft grade of contrast is no problem, but getting a hard grade is, well, hard.

Murray

Tom Duffy · Apr 14, 2006

RJS said:
I think Paul Butzi mentioned an LED safelight on his web site. I tried to find the maker and couldn't. Maybe you'll have better luck. It sounded terrific!

Calumet makes an amber LED safelight. they work great. cost about 149 dollars but good for 100,000 hours. I recommend them.

Jon King · Apr 15, 2006

MurrayMinchin said:
Did you use Blue or Royal Blue, and what grade would you estimate they gave you in contrast? I hear getting a soft grade of contrast is no problem, but getting a hard grade is, well, hard.

Murray

I used royal blue.. The first referenece I saw on the internet was the light source by Huw Finney. If I remember he used blue, because the royal blue was not available at the time. The royal blue wavelength seems to be a better match to Ilford MG paper at least

I made a 6x7 source with 2 royal blue and 2 green. For a larger head.. I'd change the ratio of green to blue.. I have notes but forget which way off hand. I printed some prints, mostly to check out different mixing box schemes, and didn't actually measure the grades I was getting.

I use a single 1 watt red lumiled as a safelight in a bathroom/temp darkroom.. I'm guessing two would be needed the permanent room I'm working on which is the main cause of the delay in the light source.

MurrayMinchin · Apr 15, 2006

Thanks Jon. Huw's site is the one that got me thinking as well...

Murray

Robert Hall · Apr 17, 2006

Thanks Guys.

I would use red for the safelight. The others tend to fog Forte fairly quickly.

My darkroom is huge, 800 sq feet. I've loved my Thomas safe light, but it fogs the Forte. It seems that the Ilford can be printed with the safe lights on full and still make a great print. (yes, I understand the physicis of it all, it's still weird!)

I will give some of the ideas a try. And it's a good thing I'm an electrical engineer as well, what self respecting photographer would know what a MOSFET is?

Here's to brighter days!

Bob F. · Apr 17, 2006

Robert Hall said:
Thanks Guys.
<snip>
I will give some of the ideas a try. And it's a good thing I'm an electrical engineer as well, what self respecting photographer would know what a MOSFET is?

Here's to brighter days!

You'd be surprised - judging from other threads and the "What do you do for a living" one, there's quite a few MOSFET huggers on here!

You might want to try the red-orange Lumiled with the Forte rather than red (I dislike red safelights: I keep hearing SONAR pinging noises in my head and expecting a bloke with a serious beard and roll-neck sweater to pop his head around the door and say something cryptic about periscopes and code books...). At 617nm wavelength, they should be far enough away from the paper's sensitivity. I use amber (590nm) with Ilford and Kentmere VC happily - not tried Forte.

Cheers, Bob.

Kirk Keyes · Apr 17, 2006

Jon King said:
I'm using green and blue ones for a VC head with a few red to add light for focusing.

Has onyone thought of having a few red LEDs in the head and then leaving them always on so that one could see where to place dodge and burn tools before the blue/green light exposure begins?

Kirk - www.keyesphoto.com

Jon King · Apr 17, 2006

Kirk Keyes said:
Has onyone thought of having a few red LEDs in the head and then leaving them always on so that one could see where to place dodge and burn tools before the blue/green light exposure begins?

Kirk - www.keyesphoto.com

I was planning to put some in my final head.. more to set up the negative with a more 'white' light.. hadn't though of it for dodge/burn..... guess it shows i've never used an enlarger with a red filter under the lens.. huh?

ras351 · Apr 17, 2006

Robert Hall said:
Thanks Guys.
I would use red for the safelight. The others tend to fog Forte fairly quickly.

My darkroom is huge, 800 sq feet.

Hi Robert,

If your darkroom is huge you could use the luxeons - especially if as Bob has suggested you add a dimmer. Try a 1W version first and see how you go. My 'darkroom' would be lucky if it was a tenth of your size and the normal 'bright' LED's work fine and are significantly cheaper. Go with the red if you've had paper fogging problems but there's no reason why you can't also add a switched orange/amber as well. I do Lith printing and process ortho film so I use a red safelight and keep it as dull as possible.

Cheers,
Roger.

High power LEDs

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