RGB remote LED bulb for enlarging RA-4 papers?

Mainecoonmaniac

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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?
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Nothing wrong with them at all. For 30 years, I've used a Beseler 45S dichroic head for 30+ years. I've had to replace the optoisolator on it. I used to print color much more and now I mostly use the color head for MG printing. I'm experimenting for LEDs to replace the head to prepare when the head completely dies. What spurred me on what I saw how efficient LEDs are. If I were successful, I would not have to put a cooling fan in it like my old Besleler head which can cause vibrations.
 

Berri

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halfaman said:
Halogen lamps are the next to be banned in European Unión for consumer lightning. They can't be sold after 2018.
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they are already banned in italy, for householding. You can still buy (and sell) halogen lamps for specialty applications.
 

Mainecoonmaniac

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1kgcoffee

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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?
Click to expand...
These bulbs produce less heat (no popping), require no filters. Plus, it means that I don't have to get another head. For those who don't have a dichro head but want to get into color enlarging, this is one less obstacle. I also find the hue and saturation to be more intuitive than RGB/CMY



Going to try to print a good neutral example with clean whites. It should not make too big a difference, but the Endura paper I have has been expired for about a year and a half and is sitting in 70 plus degree room, there may be slight yellowing.

I've had some success with a cheapo made in China bulb but the exposure times were way too long. Sounds like a lot of work and you'd probably need to swap out capacitors too.
 
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1kgcoffee

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Alright, I cut up some endura today and made a few test prints. I'd be very interested in feedback from those who think the color is off. Too much or too little RGB? Help me get there, I think it's close. Good news is that paper does not seem to have any natural yellowing. Before you look at test prints, have a look at the color wheel (HSB) to get an idea of hues:



Test 1:
f11 8sec
329 hue, 40% saturation. Leaves too yellow, shadows too red. We need to add red to exposure (make it more saturated)
Portra160-Endura-Test001 by Aaron, on Flickr

Test 2:
f11 8sec
329 hue, 45% saturation. Same as above. Also seems underexposed. Repeat.
Portra160-Endura-Test002 by Aaron, on Flickr

Test 3:
f8 7sec
329 hue, 60% saturation. Greens seem better, but we need to move more towards red on the color wheel (=more blue on print). Add a little exposure
Portra160-Endura-Test003 by Aaron, on Flickr

Test 4:
f8 9sec
342 hue, 45% saturation. Holy purple batman! Greens are now good, but there is a purple cast. Lets tone back halfway
Portra160-Endura-Test004 by Aaron, on Flickr

Test 5:
f8 8sec
336 hue, 45% saturation. Still purple. Result seems to be somewhere between Test 5 and Test 2. Lets tone back halfway again. Reduce saturation to warm image.
Portra160-Endura-Test005 by Aaron, on Flickr

Test 6:
f8 8sec
333 hue, 42% saturation. Somewhat happy but needs more tweaking. Too warm. Needs more saturation (=colder) perhaps? Or a higher hue (more blue in image and less green)?
Portra160-Endura-Test006 by Aaron, on Flickr
 
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Berri

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you are complicating things...Endura prints beautifully with halogen lamps. Anyway, after all your test I would say that the use of those kind of lamps is to avoid. But if you feel stubborn and want to see if it is possible to use them I would procede as follows: Make a print on that paper using the normal method (aka tungsten lamp) and see if the negative is capable of producing a good print. Then see if you manage to get the same result with your RGB lamp. This appears to be really time consuming and very little intuitive. I am also thinking about this, since you are using a HSB levels, why dont you tweak them in PS untill you find good values and then see if they can apply to the real print?
 

John51

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1kgcoffee said:
I've had some success with a cheapo made in China bulb but the exposure times were way too long. Sounds like a lot of work and you'd probably need to swap out capacitors too.
Click to expand...

It's the control circuitry that holds the promise imo. About £10 for electronics that can remotely control the light in your enlarger.
 

mnemosyne

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To be honest, they all look more or less terrible to me. But something is fundamentally wrong here, the white border/margin area has a different tone of white, blue or yellow on each print. It should be always the same white. Could there be an underlying cast introduced when scanning or photographing the prints? Or something with your process is way off. I also have the impression that the color casts are not uniform over the entire picture area.

Is the negative home developed? For such tests you should use a known good negative that has been processed in a tightly controlled lab.

I fully agree with Berri that you should first make a perfect print with a standard lightsource halogen lamp. Or have it done by a pro lab if you can find one that still does optical enlarging. Use this as a reference and try to match it as closely as you can with your LED setup. Motives like plants, flowers, sky etc. are deceiving as their colors usually leave a lot of leeway for interpretation until they look definitely OFF. Better to use a color chart or something that contains a neutral grey as reference and possible also some skintones. This makes detecting color casts much easier.
 

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1kgcoffee said:
I also find the hue and saturation to be more intuitive than RGB/CMY
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mnemosyne said:
To be honest, they all look more or less terrible to me.
Click to expand...

I'm afraid I'm in agreement with mnemosyne.

But in reference to what you find "intuitive", I find your outlook interesting.
I come from a background where I did a lot of analogue colour printing in the past. There is no "saturation" control in that world - you control exposure length and relative amounts of colour filtration. I've worked with both additive and subtractive based systems.
Without any means (other than exposure length) to control saturation when printing optically, I wonder whether your method is appropriate for the materials.
Ironically, when I am working with digital controls I find the hue and saturation approach to be unwieldy and awkward, and much prefer to work with individual colour channels.
 

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I would suggest using a gray scale for tests, or better yet a color chart with a gray scale. These allow you to more readily see correct color balance and any crossover.
 

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MattKing said:
Without any means (other than exposure length) to control saturation when printing optically, I wonder whether your method is appropriate for the materials.
Click to expand...

I'd have to agree. Saturation is an inherent property of the paper or film, and can't be altered in the exposure stage. I can look at a sample print and see if there is a colour cast and correct and I can see if something is too dark or light and adjust my exposure, but I can't alter the saturation of the paper.

I'm currently planning to build an LED enlarger head for B&W printing to replace a cold light head with broken tubes. It's taken very careful consideration of what wavelengths the LED's produce to be able to obtain the full range of contrast, I imagine for colour printing it becomes that much more complex to match the entire light spectrum to the paper.
 

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Here's an article I clipped from the web years ago. The website is no longer up.
 

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Craig

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Mainecoonmaniac said:
Here's an article I clipped from the web years ago. The website is no longer up.
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Looks like he went around the required spectrum! Paper needs Royal Blue LED's to develop maximum contrast, not blue or UV. Green is for the low contrast. The blues tend to bleed into the green spectrum, making it impossible to achieve a true grade 5.
 

Berri

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Craig said:
I'd have to agree. Saturation is an inherent property of the paper
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when the OP talks about saturation, I think he referes to the saturation of the emitting light. The vector going from the center (white, less saturate lght colour) towards the outer part of the circle (deep colour, more saturated)
 

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I find the results not too bad for this kind of lamp.
Also it is nearly impossible to judge colors at a PC screen which may be not calibrated.
One problem could be, that such LED lamps are not temperature stabilized. LEDs are very temperature sensitive (variation of output power as well as shift of the wavelength).But if your darkroom has a nearly constant temperature, this should be okay.
With changing Hue, you cange the relation of Y and M when compared with a traditional enlarger head. For example changing Y60 M30 to Y40 M30 is the same like changing Hue.
Saturation is the same like the level of both Y and M. It is the filtration intensity. For example changing Y60 M30 to Y50 M25 is similar to the saturation change.
A cyan to red cast is adjusted with saturation and a yellow to blue or magenta to green cast is adjusted with Hue.

You really should use a test picture to do experiments or include a grey step in the picture. A combination of many different colors plus grey step plus skin tone is the best for testing.

Craig said:
Paper needs Royal Blue LED's to develop maximum contrast, not blue or UV.
Click to expand...
UV or near UV (405nm) is very good for the blue sensitive of Multigrade or standard BW paper.
But also "royal blue" 450-460nm should work.

I find this thread very interesting. It is the first time I see real results using an LED lamp for color printing.

Joachim
 
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1kgcoffee

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What filtration settings do you folks use for CMY or RGB on Endura (glossy) for Portra (160,400,) Ektar, Gold 200 and Fuji 160NS? I'm going to try converting from those values to HSB and do some tests with various emulsions.

It's possible its this particular roll was processed incorrectly, maybe temperature off, or bad blix causing leukocyan dyes to form (Arista/Argentix kit). I will try with other negatives that scan better. Ill admit the processing of the paper was a bit off. I keep the ra-4 between 35-40c and blix at least as warm. These are official kodak chemicals. But results are fairly consistent regardless. For stop bath I have been using ilfostop recently. The edge colorcast does appear in the actual test prints. I think this may be a result of my darkroom having light leaks.

Going to do more test prints. But I can tell you the richness of these prints and simple tweaking in photoshop leaves me hopeful. I've never seen such rich prints in digital.
 

Berri

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1kgcoffee said:
What filtration settings do you folks use for CMY or RGB on Endura (glossy) for Portra (160,400,) Ektar, Gold 200 and Fuji 160NS? I'm going to try converting from those values to HSB and do some tests with various emulsions.
Click to expand...
We simply could not answer your question because it depends on many variables. It can differ from roll to roll if it was processed differently, every batch of endura paper I used was slightly different, my filters are not like yours, therefore 40Y could be a different value on your enlarger, different light bulb and so on. In one word, there is no way you can achieve good results with the filtration anybody would give you. This is not the right approach for colour printing
 
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1kgcoffee

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After more testing, the prints from my portra 400 roll look almost identical to the scans (except contrast which is higher in the print.) I think it may be a problem with the processing of the 160 roll (I was also having trouble with the scans.) The shadows are too red. Is this normal for underexposed areas in c41 prints or this something attributed to processing? I'll post examples once they are dry, for peer evaluation. In the meantime here is a diagram of the HSB color wheel and how it corresponds to CMY. Brightness does not appear to affect color balance, so it's entirely Hue and saturation. Keep in mind portra seems to print well at 333hue, 0.45saturation (halfway between rasberry and the center of the circle.)

cmyk-HSB by Aaron, on Flickr
 
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1kgcoffee

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Two more photos taken on the same evening. I will note that the borders on these prints are perfectly white in real life. They may need to be rescanned.

333 hue, 45% saturation. It was oh so close, but I feel a little cyan. The next image, I dialed down the saturation.
Portra400-Endura-Test002 by Aaron, on Flickr

Whatever color you move away from on the circle is what's added to the final result. So more rasberry in this one. I might tweak it further. This one I feel is a little too magenta therefore in a future print I'll reduce the hue by moving a couple points toward magenta. All done testing for tonight. After testing portra I'll return to kodak gold
Portra400-Endura-Test003 by Aaron, on Flickr
 

JoJo

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You really should use some test patterns.
Late evening sun and blue shadows are not the best test objects. Such pictures cannot be filtered correctly, not with RGB-Led and even not with halogen lamp.
Maybe you sould try to make a neutral grey step. Use an unexposed strip of the film for the red mask and do some exposing steps.
This will show if your setup can produce a neutral grey.

Joachim
 

mnemosyne

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Funny colors. IMHO you are wasting your time with these home developed negs. Obviously it doesn't help that you chose scenes with very difficult lighting situation. If the direct scans from your negs look similar to the scanned prints presented above, something is fundamentally wrong with your film processing. I cannot see how a normally exposed and processed negative can have a heavy magenta cast in one area of the picture and a heavy cyan cast in a different. If have already written above that the color casts appear to be non-uniform across the picture area. Anyway, there are so many variables in your workflow and only one of them being out of spec would be enough to screw up the results royally. You have already been given good advice how to proceed systematically, so I suggest that you stick to that advice
  1. use a blank negative from a professionally processed strip of CN film and try to print it to neutral, middle grey. This will tell you if your LED light source is consistent in uniformity and/color. I am not entirely sure that is the case. If you cannot get a consistent grey over the whole picture area the light source is not able to illuminate the negative uniformly and therefore all further testing meaningless. If you are able to achieve a good, uniform grey, proceed to #2
  2. use a picture of a color checker and neutral grey tones taken in uniform, normal daylight, carefully exposed and processed by a professional lab; do not use any home processed negatives
  3. Have the negative printed or print it yourself using a halogen lamp as a light source to match the neutral grey and colors as closely as possible
  4. Switch to LED light source and try to match the above print as closely as possible
 

MattKing

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For a couple of years I worked as a colour printer. We just did printing - no colour film processing. All of our work was for professional photographers - many of them portrait and wedding photographers.
One of our customers tried to economize. He did his own C41 developing and then sent the film to us to prepare proofs.
We had to "fire" him as a customer, until he agreed to supply us with properly developed film.
Until then, any print we did for him showed strong crossover and unnatural colour casts.
I'm afraid your results in this thread look worse..
If you want to calibrate a different light source for colour printing, you need a good, properly developed negative of an appropriate subject photographed under good light as a source, and a high quality print made from that negative as a reference.
 

Berri

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mnemosyne said:
MHO you are wasting your time with these home developed negs.
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the problem it is not the home developed negatives. I've been doing it for years and I get proper results every time. The OP should learn how to print coplour properly
 

Berri

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come on..
 

MattKing

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Berri said:
come on..
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For clarity, it wasn't that it was impossible for someone other than a lab to develop film properly.
The problem was that he was unable to develop film properly.
He was using equipment that was not working properly, and he was not suited to either getting it to work properly, or to use it properly once it was working properly.
He was also chronically short of money.
Some photographers are not well suited to procedures that benefit from care and attention and accuracy of detail. He was one of those photographers.
 
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