RGB remote LED bulb for enlarging RA-4 papers?

1kgcoffee · Dec 1, 2017

So modern RA-4 papers do work with old style enlargers, but they are optimized for LED lighting. I think I've found a simple solution, has anyone tried RGB LED light bulbs that are remotely controlled over bluetooth?

https://www.aliexpress.com/item/E27...t-lighting-lamp-color-change/32740086751.html

You can select an RGB colour on your cell phone, which means that it will be additive style printing. But also that we don't need dichroic or complicated xenon flash units. Just change the bulb in your enlarger. I'm excited to try this.

-1kgcoffee

MattKing · Dec 2, 2017

The LED lighting used in modern commercial printers is likely of a very highly controlled portion of the colour spectrum. I'm not sure that you will be able to achieve the necessary colour control with the sorts of bulbs you are linking to.

maltfalc · Dec 3, 2017

rgbw is not the same thing as rgb.

DREW WILEY · Dec 4, 2017

Papers differ. But this has nothing to do with LED bulbs, which still lack the spectral accuracy and power for realistic color printing. Some printers like Lightjet use RGB lasers for RA4 papers. I use both additive RGB colorheads on enlargers, and conventional YMC subtractive colorheads. Both employ halogen bulbs.

1kgcoffee · Jan 25, 2018

Guys, I'm happy to report that it does work, and extremely well. At least for Ektar on crystal archive.

The bulb I purchased was a lifx (75watt equivalent.) Cheap bulbs do work but lack the output to print stopped down in reasonable time. You need something with a high light output to make this work well. The lifx is $75, but can be used in a condenser head for graded printing WITHOUT graded filters, and color RA-4.

It uses a different system than additive or subtractive printing. Rather than RGB or CYM, it uses HSB (hue, saturation, brightness). I find this to be more intuitive than RGB which takes a lot of back and forth. Once you find the correct hue for the mask, saturation needs to be pumped up just enough to clip it, before the image tends to blue. Brightness, I'm not sure needs to be adjusted at all. On Ektar, this translates to about (0,64,100) This makes a lot of sense.

As for the quality of the prints themselves, I'll try to post a few examples in the coming days but I am very pleased.

There is one issue, which is that these bulbs take a second to power on. If you have a longer printing time (10 seconds), this shouldn't matter. Or just stop it down. If shorter, cover the enlarger with your hand for that second.

Rudeofus · Jan 26, 2018

I am not surprised that this works. With full control over all three color channels you have full control over the exposure of your paper, what more can you ask for? The only limiting factor is light output: most enlargers use quite strong light bulbs, and there is nothing available with LEDs, at least not with a comparable form factor.

darkroommike · Jan 26, 2018

I'm sure there are a lot of commercial printing labs still using conventional halogen lamps for printing on the new papers, they don't scrap huge investments in technology every time a change comes along. The "S-type" printer I used to use had a huge halogen lamp, 1000 watts as I recall, a hot mirror and then a set of filters on solenoid "paddles" to control exposure and then a shutter. The lamp burned continuously.

DREW WILEY · Jan 26, 2018

Continuous heat can be brutal on filters, as well as on maintenance and utility expenses. That's why I got rid of my Durst 2000W color mural head and replaced it with pulsing RGB.

Photo Engineer · Jan 26, 2018

I checked with the guy in charge of Endura paper development (no pun intended) and he told me that either white light or RGB would work. It is more a matter of reciprocity across the broad exposure times used than anything else.

PE

mshchem · Jan 26, 2018

Sounds like a great opportunity for a cell phone app to control the bulb. I will stick with what I have as I AM too old to learn
Mike

1kgcoffee · Jan 26, 2018

PE,
Thanks. That's great news as I actually ordered close to 900ft of endura earlier today. I'm sure exposure times can be kept low enough not to have any problems with this powerful bulb.

mshchem,
If your setup works and your happy with it, no reason to get on this new bulb. I can totally respect that. But I think this will be perfect for those new to printing color or black and white. As someone new to printing I almost didn't try ra-4 as it seemed too complicated. But it's really not. I plan on posting an RA-4 tutorial here aimed at the beginner, with my newfound knowledge. Now anyone with a condenser head can get into ra-4 easily. It is more rewarding than black and white in my opinion.

Also, the existing app controls it pretty well, but theres an API and it's capable of strobe or color change intervals. With a simple app you could do some power graded or split grade printing with only a few sliders.

Drew,
Are you talking about the minolta 45a? I have this head and love it. Problem is the expensive flash tubes.

Leadmonkey · Apr 8, 2018

Hi, 1kgcoffe. Can you post a few examples printed with this lamp?

Gerald C Koch · Apr 8, 2018

DREW WILEY said:
Papers differ. But this has nothing to do with LED bulbs, which still lack the spectral accuracy and power for realistic color printing. Some printers like Lightjet use RGB lasers for RA4 papers. I use both additive RGB colorheads on enlargers, and conventional YMC subtractive colorheads. Both employ halogen bulbs.

+1

Not all LED's provide the right colors. Experiment.

DREW WILEY · Apr 8, 2018

Just noticed I never responded to a question from January. No, I don't use a Minolta 45A. My colorheads are customized using both unique and cannibalized components. My 8x10 additive RGB colorhead uses multiple synchronized halogen bulbs, and in hundreds of times brighter than the Minolta. Powerful RGB heads using pulsed xenon did once exist, but for sequential color separation enlargements in the printing industry. Some of these ran so hot the heads required a water-cooled outer jacket.

1kgcoffee · Apr 10, 2018

Leadmonkey said:
Hi, 1kgcoffe. Can you post a few examples printed with this lamp?

Yes, in a little bit. Been a very busy winter for me but I have managed to nail settings for Kodak Gold 200 and Portra 400. It works really well.

1kgcoffee · Apr 23, 2018

Leadmonkey said:
Hi, 1kgcoffe. Can you post a few examples printed with this lamp?

Alright, so I printed a few test strips on Endura just to give you an idea of color, waiting for them to dry. One of Portra 400 and the other Portra 160 using the filtration settings for Portra 400 (331degrees hue, 41% saturation). They seem to match, but more tests are needed. So far I have nailed Portra 400 and Kodak Gold 200 on Endura. Overexposed images use similar hues but require more saturation to cut through the mask. Currently waiting for these to dry.

First image is one of the first I printed with LIFX, ektar on fuji CAII lustre finish. The filtration isn't tweaked 100%, it's a little too saturated. I started printing on endura shortly after and ditched CA before bothering to get it perfect. Had to discover new settings. But the hue (zero degrees, I think 50% saturation) is correct. So maybe 45% saturation would work. When you nail hue, Less saturation gives warmer colors and more saturation gives colder colors. It's fairly intuitive compared to CMY or RGB when you get the hang of it. Anyways straight scan:

Ektar-CAII-Test by Aaron, on Flickr

I think Fuji CA-II may be better for ektar as endura has stronger contrast.

Here it is with color balance shifted warmer in PS, just to prove that the colors are technically 'there'

Ektar-CAII-Test2 by Aaron, on Flickr

1kgcoffee · Apr 24, 2018

As promised, here are the two test strips:
35mm Portra 160, printed with settings for Portra 400

Portra160-Endura by Aaron, on Flickr

6x6 Portra 400

Portra400-Endura by Aaron, on Flickr

I have not done extensive testing with Portra 160, but it seems to be very similar in setting to 400 as you would expect.

Berri · Apr 24, 2018

1kgcoffee said:
So modern RA-4 papers do work with old style enlargers,

I print on Kodak endura premier, Kodak DIGITAL premier and fujicolor DPII paper with no issues on my halogen light enlarger. Not sure what you are talking about. This is a print from portra 160 on Fujicolor DPII

Mainecoonmaniac · Apr 24, 2018

I wonder if it would be beneficial to instead of trying to get a mix of color like the old days of tungsten lamps and approach the problem of color balance of RA paper through individually exposing the R G B LEDs? Change the color balance by adjusting the duration of exposure of each color of LED? The RGB LEDS create different colors through pulse width modulation by changing the duty cycles of each LED.

Berri · Apr 25, 2018

Mainecoonmaniac said:
I wonder if it would be beneficial to instead of trying to get a mix of color like the old days of tungsten lamps and approach the problem of color balance of RA paper through individually exposing the R G B LEDs? Change the color balance by adjusting the duration of exposure of each color of LED? The RGB LEDS create different colors through pulse width modulation by changing the duty cycles of each LED.

seriously, what is wrong with normal halogen lamps? I get perfect colour balance on modern papers. Why complicating things with all this fancy stuff that may or may not work?

halfaman · Apr 25, 2018

Halogen lamps are the next to be banned in European Unión for consumer lightning. They can't be sold after 2018.

mnemosyne · Apr 25, 2018

halfaman said:
Halogen lamps are the next to be banned in European Unión for consumer lightning. They can't be sold after 2018.

Projector lamps etc are not lamps intended for consumer lighting.

mnemosyne · Apr 25, 2018

Berri said:
seriously, what is wrong with normal halogen lamps? I get perfect colour balance on modern papers. Why complicating things with all this fancy stuff that may or may not work?

Nothing wrong with halogen lamps, but I find this thread interesting, as LED bulbs may create a relatively simple path to add color printing ability to condensor system enlargers without resorting to gel filters.
Still, the results shown here as examples do not convince me as they exhibit fairly heavy color casts. Not sure if this is due to the LED light source, processing or some post processing problems.

halfaman · Apr 25, 2018

mnemosyne said:
Projector lamps etc are not lamps intended for consumer lighting.

Correct, but it is consumer lightining lamps what people usually buy even for enlargers. Also it is the largest market by far, so it will make more difficult the availability and put pressure in price for other uses.

It happened the same thing with tungsten lamps, they still exist for special applications but in a very limited selection and higher price.

John51 · Apr 25, 2018

I've got a cheapo multi colour bulb. Not bluetooth, it came with a remote. Haven't opened it up yet but if it's hackable, then maybe the leds can be replaced with ones more suitable for printing?

Being able to remotely control the RGB output of a bulb could bring condenser enlargers back in fashion.

RGB remote LED bulb for enlarging RA-4 papers?

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