Possible LED light source for enlargers

[Neal Chaves]

Just received an e-mail promotion from Rosco for their new LED lights.
http://www.rosco.com/lighting/litepadDL.cfm?menuReturn=lighting
The "LitePad" DL and HO+ daylight units look like they could make a good enlarging light source, especially the 12X12 size for an 8X10 enlarger.

I have a Beseler 8X10 with a 12X12 Aristo cold light head and I will measure the output in FC at 12" and compare to the specs on the Rosco 12X12 LitePad.

It is only 8mm thick. If one were made to carry a negative with a hinged ANR glass to the same size as an 8X10 or larger film holder, it could slide into the back of a view camera to make it an enlarger.

[ic-racer]

I have had little respect for 8x10 LED light sources as being too dim, however, after seeing this years Le Mans race (LED headlights on the cars) I'm expecting something like this.

I think I can actually compare the stated output to my 2000W Durst CLS2000. The specs on the 12x12 unit indicate an output of 3200 LUX at 6". That would be close to EV10 with ISO 100 film. I suspect it would not be too much trouble to reach my incident meter through the 8" lens opening and measure the output of the Durst mixing box about 6" away.

[ic-racer]

The answer is....LED still not as bright, but probably bright enough for many applications. I suspect the technology will continue to progress.


CLS2000 at 6" = EV14 = 40,960 LUX
ROSCO 12x12 LED panel at 6" = EV10 = 3200 LUX

[Paul Ewins]

Would this be usable with VC papers? Do white LEDs have enough of the spectrum to enable the use of traditional VC filters?

[vinny]

NO. I doubt they'd be suitable. I've used the original lite pads extensively for motion picture work and they aren't that bright. Now the Tungsten Lite Panel 1x1 (litepanels.com) would be closer.


Just received an e-mail promotion from Rosco for their new LED lights.
http://www.rosco.com/lighting/litepadDL.cfm?menuReturn=lighting
The "LitePad" DL and HO+ daylight units look like they could make a good enlarging light source, especially the 12X12 size for an 8X10 enlarger.

I have a Beseler 8X10 with a 12X12 Aristo cold light head and I will measure the output in FC at 12" and compare to the specs on the Rosco 12X12 LitePad.

It is only 8mm thick. If one were made to carry a negative with a hinged ANR glass to the same size as an 8X10 or larger film holder, it could slide into the back of a view camera to make it an enlarger.

Paul,
they do require color correction when used for motion picture work because there is a bit of a green spike.

[Arne Croell]

Would this be usable with VC papers? Do white LEDs have enough of the spectrum to enable the use of traditional VC filters?

I assume filters in front of white LED's will change the grade in the desired direction, but probably in quite different steps than the filter number suggests, so a recalibration of the grades would be necessary. The VC filters are made for continuous spectrum incandescent light sources, and white LED's are a pretty far cry from that. Most of them just use a blue LED plus a phosphor that absorbs part of the blue and then emits in the yellow(ish) spectrum. The CRI of most white LED's is therefore well below 90.

That being said, if you have one of those panels, experimenting doesn't hurt.

[Steve Smith]

The answer is....LED still not as bright, but probably bright enough for many applications. I suspect the technology will continue to progress.

It is progressing. The company I work for specialises in placing LEDs (and other components) on flexible polyester circuits. We do work for this company: http://designledproducts.com/ on various lighting products, some of which are shown on their website.

LEDs will soon be a viable replacement for fluorescent (and tungsten) lighting. In fact, it is already. We are soon going to have all of our office lighting replaced with LED panels.


I assume filters in front of white LED's will change the grade in the desired direction

I'm not sure. I have red, green and blue LEDs in my enlarger and change contrast by varying the green and blue LEDs. I am going to try white soon though.


Steve.

[Arne Croell]

I'm not sure. I have red, green and blue LEDs in my enlarger and change contrast by varying the green and blue LEDs. I am going to try white soon though.

Steve.

I use blue -green LED's too (I have both the Calumet and the Heiland LED heads) and they work fine. No reason to change that. What I meant with "in the right direction" is, that if you use a yellow filter in front of a white LED panel, you will get a softer grade, and a harder one for the magenta filters - there will be some effect. How big that change is, whether it is close to what the filter no. implies, and if it is possible to reach really soft or really hard grades, is a totally different story and has to be tried.

[Steve Smith]

I think you are right, you will push it towards harder or softer grades but I don't think you will get near to grade 0 or 4. I think my blue and green LEDs give me about 1.5 to 3.5 at most. I wouldn't expect even that range with filtered white LEDs but I wouldn't mind being proved wrong!


Steve.

[ic-racer]

I noticed the parking garage where I park changed over totally to LED lighting. Something like these 16"x16" (external dimension) units. That looks more like something to sit on top of an 8x10 enlarger: http://www.lsi-industries.com/documents/datasheets/xpg3-datasheet.pdf

77431

Since the price on these is secret, so they can scam institutional clients I suspect, I wouldn't be surprised if it cost more than a second-hand Durst CLS2000 head.

[konakoa]

Would this be usable with VC papers? Do white LEDs have enough of the spectrum to enable the use of traditional VC filters?


I think you are right, you will push it towards harder or softer grades but I don't think you will get near to grade 0 or 4. I think my blue and green LEDs give me about 1.5 to 3.5 at most. I wouldn't expect even that range with filtered white LEDs but I wouldn't mind being proved wrong!

Yes, white LEDs work fine for VC paper. I've built two 4x5 enlarger heads from scratch using white LEDs as the light source. The spectrum of white LEDs is continuous for the entire visible spectrum; however there is a very small gap in the blue portion. I checked this visually with a homemade spectrometer.

I also ran practical printing tests with a Stouffer 21-step print wedge. I compared white LEDs to regular tungsten and florescent 'cold' lights, with and without VC filters. In all cases the white LEDs worked well, and I was able to reach any of the print grades from -1 to 5+ with white LEDs. Individual blue and green LEDs alone are a different story.