Customized 8x10 Codelite LED Head for Variable Contrast

[Richard Rau]

I came across a company in Denver called Customized Designs that creates customized Color LED Display modules for Bars, Furniture, Display models, etc. and was wondering if anyone has ever heard of something like this to create a Codelite Head for a replacement for an Aristo Coldlight head to print Variable contrast. A friend of mine had a multi-level one created to display his Bourbon collection behind his bar that changes colors and lights up from underneath. However you can program the remote to display various intensities of specific colors, for instance from greeen > cyan > blue, and lock in those colors. The transition between the colors seemed very smooth and you could program it to be repeatable as he demonstrated to me. Naturally I had other thoughts for such a display in mind. And they make custom boxes to whatever size or shape you desire. I haven't investigated prices yet. Just wondering if anyone has any thoughts on this and if it seems feasible, or has anyone ever had something like this made for Variable contrast printing?

http://customizeddesigns.net/lumen_20x20.php#.UgmxvnDA421

[Drew Wiley]

There are a number of people contemplating making an LED replacement for cold lights. The main question at this point would be in the standardization for the electronics and bulbs themselves. It is a category of lighting evolving quickly, so I'd want to see a little more track record before putting my neck on the block.

[Eric Biggerstaff]

Check out:

http://www.modernenlargerlamps.com/Welcome.html

Great company and the owner is excellent to work with.

[Drew Wiley]

The key would be to find a blue-green LED bulb suitable for split printing. It would be easier to design a head this way and simply filter below the lens than to design
a light bank with two different kind of bulbs. I have some sample LED panels coming in, but they're white light ... at least a starting point to see how well they filter.

[Jerry Bodine]

I've recently done an LED mod to my E6 (5x7) Omega - the one with the Omegalite "saucer" head that used a Circline fluorescent bulb for graded paper. The mod is similar to the description provided in this (http://www.largeformatphotography.info/forum/showthread.php?81261-Converting-Omega-E3-Cold-Light-Head-to-LEDs-for-100&highlight=omega) post, using the same LEDs, driver, and attachments to the heatsink.

However, I installed a finned heatsink inside the lamphouse just to be safe, as I didn't want to add holes in the lamphouse to aid natural venting. That necessitated placing the driver on the top of the lamphouse (outside) - not a big deal. The result was a lamphouse that is barely warm to the touch. Inside the housing I made a support for the heatsink that also held two separated diffusers for even illumination, using MDB material, and painted it bright white. My first trial involved use of standard milky white acrylic material for the diffusers, but found a serious light output deficiency and apparently a color problem that prevented any "grade" above #3. After much research for a different diffusion material, I found a new-to-market diffusion material designed expressly for LEDs that solved both problems.

I'm using Ilford's under-lens filters and have just completed some thorough tests with Ilford's MGIV glossy and their MG dev (1+9), 4x5 Stouffer 31-step wedge in carrier, 00-5 (no half-grades). For the extremes, I also checked out #47B (blue tri-color gel) and #58 (green tri-color glass). The 47B offered an insignificant increase in high contrast, but its output was half that of #5 and wasn't practical. The 58 offered some lower contrast than that of #00 but likewise was not practical due to output loss. So split printing should be fine. Without any filter, a smooth curve matched #2 at high density and fell between #2 and #3 in the mid-range. The 4x5 step wedge was focused on an approx 8x10 area with a 150mm Componon. An exposure of 15 sec at f/8 produced a density of 2.06 (Step 1) to a density of .02 (Step 25) with #00 filter. So output may be lacking for 16x20 enlargements. We'll see.

Illumination was very even with no lens. Introducing a 210mm Componon, simulating 11x14 enlargement, showed corner falloff about 2/3-stop at f/5.6, and no falloff at f/16 and beyond. Probably could have used more LEDs near the corners, but I can live with it as is.

12 LEDs are Cree's 3w Premium XP-G Cool White (7500K). Bought two extras for spares. The spectrum shows a sharp rise from 410nm (0% intensity) peaking at about 448nm (100% intensity), tailing off sharply to about 480nm (20% intensity), then slowly rising to about 535nm (80% intensity), them slowly falling to 700nm (0% intensity).

[Peter De Smidt]

Jerry,

What diffuser material did you use?

[cardiomac]

I have available on my website an LED VC enlarger head for the Omega D series 4x5 enlargers. It works very well and users, some of whom post on this forum, have been very pleased with it.

Recently Eric Biggerstaff and I have developed a 5x7 white light head for the Omega E6 enlarger using 6 Cree XM-L warm white LEDs. The light is very bright and even. The design could be modified to become a VC head if desired. Eric's assistance was invaluable to the success of this project and it was very appreciated. The lamp could not have been made without him. A picture of the completed lamp is attached.

Redshift, of this forum, recently built an 8x10 lamp house for his home-built Sinar enlarger using white LEDs. It will be possible to modify it in the future to be a VC head using blue and green LEDs and an appropriate controller.

Conceptually, making a VC head from blue and green LEDs is easy. However, making a practical, durable, professional grade unit is not so easy. The biggest issue is how to control the relative brightness of the LEDs. Just putting the LEDs on rheostats is not an option for lots of reasons. For one, to keep midtones constant when changing contrast, you have to decrease the brightness of one color while increasing the brightness of the other. Unfortunately, VC paper is not sensitive equally to blue and green light, so it gets complicated very fast. That's why I chose in my Model 3 design to use an on board micro-computer to control the LEDs. But then you have a new problem which is how to control the computer. You could build a custom box with all sorts of switches and displays but that's expensive and, moreover, limiting in that new features cannot offered retroactively to customers who purchased earlier units. That's where the iPhone comes in - as a wireless, programmable interface to the onboard computer in the lamp head. Having a custom app on the iPhone as the means of controlling the light output of the head makes printing easy, as it should be, and new features can be made available to everyone via an app update.

With that being said, there are lots of ways to achieve the same result and I would encourage anyone with the inclination to experiment to do so on their own. It is exciting to see interest in this LED technology which is really ideally suited for photographic enlargers. Feel free to contact me if you want any advice or just have questions you think I may be able to help you with.

[cardiomac]

Check out:

http://www.modernenlargerlamps.com/Welcome.html

Great company and the owner is excellent to work with.

Thanks, Eric. It was a real pleasure to work with you too.

[Jac@stafford.net]

Check out:

http://www.modernenlargerlamps.com/Welcome.html

Great company and the owner is excellent to work with.

What a great reference! Clearly the engineer has worked out the details very well. Thank you.

[Sal Santamaura]

Everything else pales in comparison to this


http://heilandelectronic.de/led_kaltlicht/lang:en,


both with respect to elegance of design and price. :) For 8x10, unless you've just won the lottery, investigate the approaches others have already suggested.

[Drew Wiley]

Sal, it should be simple in principle to make a large affordable LED replacement for a cold light. Making an efficient LED colorhead is a completely different question. I'm very skeptical that at this point in time there are tricolor LED's with tight enough spectral characteristics to do a good job of it. And if you had to go and filter each bulb to properly sandwich each respective bandwidth, you'd end up with something far more complicated and expensive than an ordinary halogen colorhead. But this is obviously a category of technology worth keeping an eye on. As someone who works with true additive color enlargement, and knows the distinction between the result and more generalized subtractive methods, I'd would view progress as anything looking backwards in terms of color purity. And I see no evidence the proper kind of LED's even exist yet, much less can be operated in some standardized fashion which can be electronically maintained over the long haul. Sophisticated lighting controls run the risk of rapid obsolescence just like software itself.

[Sal Santamaura]

Sal, it should be simple in principle to make a large affordable LED replacement for a cold light. Making an efficient LED colorhead is a completely different question...The OP asked about a VC black and white head, not a colorhead. The Heiland design, while neither simple nor inexpensive, does what he seeks. Not only does it come with an integral controller programmed for the specifics of VC papers on the market, the firmware for which is updated as necessary and made available for free download, it also incorporates graduated neutral density filtration that ensures absolutely even illumination from center to corners.


...I'm very skeptical that at this point in time there are tricolor LED's with tight enough spectral characteristics to do a good job of it...As someone who works with true additive color enlargement...I suspect that, as time marches on, you will be one of fewer and fewer people doing analog color printing. While RA-4 paper and chemicals may continue to be produced for some years, ever-decreasing numbers of people actually making prints from their digital files will probably drive the few who do desire hard copy to inkjet. Unless you've stockpiled a large quantity of paper and chemicals, your color enlarging days are numbered. Given that, only a DIY LED colorhead appears viable; there simply isn't enough market for commercial manufacturers to develop one.

[Jerry Bodine]

Jerry,

What diffuser material did you use?

Peter,
This should save you a lot of looking. I chose Makrolon® LD polycarbonate sheet, .118” (3mm) thickness, Std color B-48 white. I used two sheets, adequately spaced above the negative carrier and between the two sheets. It’s made by Bayer MaterialScience with distributors everywhere. I have about a half dozen distributors near me, so I got a sample sheet from one of them, enough for my diffusers and spares. Using saber saw and blade with 40 teeth per inch, it leaves a smooth edge that requires no further work. I clamped it between two thin sheets of MDB board when cutting, just to ensure a good cut. Here’s a blurb on the material:

LD polycarbonate sheets deliver uniform light diffusion for today’s LED signage. They feature an advanced light diffusion technology that provides excellent light uniformity. LED hot spots and shadowing are eliminated in flat or formed applications. Makrolon LD is available in a range of standard sign colors and can be custom matched to industry colors. Don’t limit your design flexibility with LEDs. Makrolon LD delivers now.
Call 800-254-1707 for samples or visit www.sheffieldplastics.com to locate your
local, authorized distributor.

Distributor search: http://www.sheffieldplastics.com/distributor_search.cfm?nav_id=9,0,0,0

Material properties: http://www.sheffieldplastics.com/web_docs/pds/PDS097_LD.pdf

[Peter De Smidt]

Thank you, Jerry.

[Drew Wiley]

Nonsense, Sal. Nearly all high-end digital printing is done with exactly the same paper and RA4 chem as I use in an analog darkroom. RA4 is is no imminent danger
whatsoever. The fact is, it is not only much more economical to print than inkjet, but than even traditional black and white on decent papers, and the quality is capable of being second to none at this point in history. The high-decibel marketing propaganda engine of the consumer electronics industry might tell you otherwise, but not the facts. The only difference between me and someone using a Lightjet is that I don't even need to scan, and unless I had my own drum scanner, I can produce quality at least as good or probably better at about 10% the overhead. Yet even the general price advantage of RA4 versus wide format inkjet is another reason it will continue to be preferred in many cases. The seamless look is different too. Last of my worries. My biggest problem at the moment is simply getting around to changing a ten buck lightbulb, not worrying about some imminent obsolescence of hardware of software for some half million dollar machine. Same reason turtles and crocodiles outlived the dinosaurs. Some less fancy things just make sense in the long run. But I am aware that Heiland device
is intended for VC printing, not color ... but if the right bulbs did become avail someday, they could use it as a prototype for a color as well as b&w cold head.

[Drew Wiley]

"Sign white" acrylics and polycarbonates are available from all the major sheet plastics sources. They are not truly Lambertian like opal glass, so sometimes require
a spaced double layer or some other means to even out the overall area. Traditionally, thick white acrylic was custom ground to match the combined falloff of both
the head and a particular enlarging lens. Therefore, you'd hypothetically need a different diffuser for different lenses, unless like me, you try and use longer than
"normal" focal lengths with little falloff. Having a programmable way to do this sounds interesting, but given the fact that most mfg corps don't stay in business very
long at all these days, the possibility of free firmware updates doesn't exactly give me a lot of comfort. That's what Kodak promised to a lot of labs who actually paid
a ton of money for the service, then got left hanging just two years later. If I can't fix it with a soldering iron and locally avail simple components, no thanks.

[Sal Santamaura]

...I suspect that, as time marches on, you will be one of fewer and fewer people doing analog color printing. While RA-4 paper and chemicals may continue to be produced for some years, ever-decreasing numbers of people actually making prints from their digital files will probably drive the few who do desire hard copy to inkjet...


Nonsense, Sal. Nearly all high-end digital printing is done with exactly the same paper and RA4 chem as I use in an analog darkroom. RA4 is is no imminent danger whatsoever. The fact is, it is not only much more economical to print than inkjet...Note that I wrote nothing about economic advantage or imminent danger. Instead, I said ever-decreasing numbers of people are actually making prints from their files. That is what will at some point doom RA-4, regardless of whether high-end digital printing uses it. This is a market-size question. If the masses cared about having prints made and the quality thereof, everyone would still be shooting with film cameras rather than cell phone cameras. It's not a question of if, but rather of when.


...The Heiland design...come[s] with an integral controller programmed for the specifics of VC papers on the market, the firmware for which is updated as necessary and made available for free download...


...the possibility of free firmware updates doesn't exactly give me a lot of comfort...Heiland has been around for 25 years. Its interactions with me have been characterized by the integrity one expects from a privately-held firm. Given the near-zero rate of new black and white paper introductions, any end to firmware updates would not be much of a loss. In that case, users are capable of programming the controller themselves after performing some trials with such new papers. I'd rather have a light source with its own stand-alone controller than one completely dependent on an external, guaranteed-to-soon-be-made-obsolete-and discarded smart phone. :D

[Drew Wiley]

I don't have a crystal ball, Sal, and won't be around forever either. Amateur album prints might be declining in demand, but still overall are a huge worldwide market.
But commercial displays are the main driver of RA4 paper. Quite a few mid-sized corps ad depts are switching to in-house wide-format inkjet, but for the bigger chains it's still much more economical to mass produce display using some kind of RA4 repro. Plenty of labs still offer it, though the number doing it optically has
diminished. As far as corporate stability in general, I'm in the unfortunate position of frequently betting against them - hundred year old corporations are disappearing like fruit flies lately. They've survived wars, and some of 'em, even the great depression.... but all it takes is an idiot at the helm to sink em in a matter of months. Our corporate culture in America has perfected the art of shooting itself in the foot... and the British, Germans, and Japanese have done a good job copying our stupid mistakes. Monkey see/monkey do mentality. ... the lemmings just blindly follow one another over the cliff. And rapid obsolescence is the deliberate name of the game in electronics. Of course, I'm not implying anything negative about Heiland per se. I wish them luck. Two of my three colorheads are
DIY anyway, simply because nobody had what I needed. But I wouldn't call any of them inexpensive projects. And there are in fact a number of people contemplating LED colorheads. It just seem premature at this point. A VC head, yeah, that's completely realistic. I hope to have some LED light panels shipped to
me in a few days just to see how well the light goes thru tricolor blue and green - just free sample from an industrial mfg I'm well connected with. Staying ahead
of the game in case my cold light wears out. But not everything that goes extinct stays extinct anymore. Woodbury type has been commercially resurrected after
a hundred years absence. Dye transfer printing has been commercially restarted in Germany, and a few folks like me have picked up some of the leftover materials
for personal use. Type C printing is capable of remarkable results right now if anyone is willing to actually get off their butt and learn it. A few people go to the trouble of handmade color carbon. ...Not everyone is satisfied with the inkjet option.

[Richard Rau]

Sal is right, I did initially inquire about Variable Contrast B&W Printing, and more specifically about an 8x10 replacement for my Aristo head. However, this is exactly what this forum is all about, spirited discussions that can lead into many different directions and opinions. Thanks to everyone who has responded so far, and who knows how technology will evolve to make this a viable and hopefully affordable alternative to using gel filtration under or in front of the enlarging lens.

[Drew Wiley]

Just makes me wonder whether they were contemplating a color LED platform to begin with.... Going thru the trouble of including a red channel just to slightly
increase brightness for dodging and burning seems like a redundant luxury otherwise. Be interesting to see what they've got up their sleeve as this kind of lighting
technology gradually spreads its wings. But their biggest competition will be from simple DIY conversions for VC, which seem fairly simple to concoct, even now.

[Captain_joe6]

Given that, only a DIY LED colorhead appears viable; there simply isn't enough market for commercial manufacturers to develop one.

Why not back up a step and devise an LED-based white-light source to retrofit existing color heads? Wouldn't that solve all the problems of color balance and light output for various colors of LEDs and whatnot? Why spend the time reinventing the wheel when all you need is a new hub? A white-light LED source that replaced halogen/quartz lamps would be much more stable and predictable over time, and wouldn't come with any of the problems associated with mixing color LEDs, and, given the spectral stability, end users would be able to work with a set of fixed correction values for their lamps to start with.

[ic-racer]

Why not back up a step and devise an LED-based white-light source to retrofit existing color heads? Wouldn't that solve all the problems of color balance and light output for various colors of LEDs and whatnot? Why spend the time reinventing the wheel when all you need is a new hub? A white-light LED source that replaced halogen/quartz lamps would be much more stable and predictable over time, and wouldn't come with any of the problems associated with mixing color LEDs, and, given the spectral stability, end users would be able to work with a set of fixed correction values for their lamps to start with.

In my workshop is easier to find, build, buy, rebuild or design a halogen lamp power supply (in fact some run off mains voltage) than it is to construct a power supply for a monster LED.

It is good to see people interested in developing new projection printing technologies, however, I believe mechanical dichroic heads will continue to perform years after microprocessor controlled units fail. The nice thing is that no one is forced to take sides, so I have both!

[Sal Santamaura]

...Given that, only a DIY LED colorhead appears viable; there simply isn't enough market for commercial manufacturers to develop one.


Why not back up a step and devise an LED-based white-light source to retrofit existing color heads? Wouldn't that solve all the problems of color balance and light output for various colors of LEDs and whatnot? Why spend the time reinventing the wheel when all you need is a new hub? A white-light LED source that replaced halogen/quartz lamps would be much more stable and predictable over time, and wouldn't come with any of the problems associated with mixing color LEDs, and, given the spectral stability, end users would be able to work with a set of fixed correction values for their lamps to start with.Sounds like an unachievable design with today's or near- to medium-term future LED technology. But go ahead if you're confident -- come up with an LED source that puts out continuous spectrum white light compatible with dichroic filters in a form factor that will fit inside existing color heads.

I doubt this will be possible until a long, long way down the road of LED development. By which time RA-4 paper would likely no longer be available. :D

[Struan Gray]

Sal, I'm interested in why you feel a continuous spectrum is necessary. RA4 is exposed with lasers these days, with no ill effects. Dichroic mirrors and filters don't care if the light is broadband or monochromatic. C41 negatives only contain three different dyes, and as long as you can choose wavelengths which unambiguously code for only one of them each (and expose only one of the RA4 components too) you're home and dry.

If everybody used monochromatic sources, you could probably dispense with the orange mask in negatives.

[Larry Gebhardt]

I came across a company in Denver called Customized Designs that creates customized Color LED Display modules for Bars, Furniture, Display models, etc. and was wondering if anyone has ever heard of something like this to create a Codelite Head for a replacement for an Aristo Coldlight head to print Variable contrast. A friend of mine had a multi-level one created to display his Bourbon collection behind his bar that changes colors and lights up from underneath. However you can program the remote to display various intensities of specific colors, for instance from greeen > cyan > blue, and lock in those colors. The transition between the colors seemed very smooth and you could program it to be repeatable as he demonstrated to me. Naturally I had other thoughts for such a display in mind. And they make custom boxes to whatever size or shape you desire. I haven't investigated prices yet. Just wondering if anyone has any thoughts on this and if it seems feasible, or has anyone ever had something like this made for Variable contrast printing?

http://customizeddesigns.net/lumen_20x20.php#.UgmxvnDA421

Richard, I didn't use that type of controller, but I did build a VC head (http://www.trippingthroughthedark.com/category/equipment/led-head/) for my 5x7 Durst. It could be scaled up to work for 8x10 either by making a stop less bright, running the LEDs at a higher power (but still within spec), or using a bigger power supply and an extras set of drivers.

If you do investigate your linked solution make sure you can control it with a timer and have the settings stay and startup time needs to be very very quick. My first attempt at LED drivers was hindered by slow dimming times or slow startup times. I imagine the are using DMX controllers, which i briefly looked at, but ultimately decided weren't quite what I wanted. They might be a good starting point for you however.

[Sal Santamaura]

Sal, I'm interested in why you feel a continuous spectrum is necessary...Dichroic filters in various manufacturers' color heads are unlikely to be centered on exactly the same wavelengths. They all assume a halogen, continuous source. I suppose one could conjure a "white" LED source that had just three wavelengths of output, but those better be aligned with the filters in whatever head it's planned for.

Form factor challenges do not seem insignificant either.

[Struan Gray]

I confess I was thinking in terms of a home-build, in which case testing and calibration just come with the territory. If you wanted to sell a replacement enlarger bulb with LEDs to people expecting to plug-in-and-play, that might be trickier.

I would guess that colour heads with a mixing box won't worry too much about form factors - LEDs are now so bright you can probably squeeze enough emittance into an area the size of a conventional bulb.

For cost reasons, I'm thinking of a programmable RGB LED in an condenser head. Getting rid of unevenness might be an issue there.

[Ginette]

Peter,
This should save you a lot of looking. I chose Makrolon® LD polycarbonate sheet, .118” (3mm) thickness, Std color B-48 white. I used two sheets, adequately spaced above the negative carrier and between the two sheets.

Thanks for this information Jerry. I wish to replace some diffusers on coldlight. For the smaller units I will try also Opal glass (I have some 8x10 sheets) but for larger size coldlight I will give a try of the product you speak about instead of regular white acrylic.
I was curious of the space you left between the 2 layers of Makrolon and above the negative? As I use coldlight, I wish it the nearest possible from the negative. I imagine also that I can use the space between the 2 sheets as a filter slot.

[Jerry Bodine]

Hi Ginette,
I made a drawing (to scale) prior to making the modification, so rather than disassembling to get the measurements you want, I measured on the drawing. As I mentioned, each of the two diffusers is 3mm thick. The distance from the top surface of the upper diffuser to the LEDs is 19mm (.75"). The lower diffuser, which replaced the original, leaves an air space of 8.64mm (.34") between the two diffusers - may be insufficient space for a filter drawer. The bottom surface of the lower diffuser is then 12.1mm (.48") above the negative. This allows very even illumination for the LED arrangement I used. I originally tried two "sign white" acrylite diffusers of the same thickness but found two problems: 1) a large loss in output and 2) an apparent color issue that limited the print results to about Grade 3. The Makrolon diffusion allowed a definite increase in output and the results to reach Grade 5. Just for the heck of it, I held a 47B tri-color blue filter under the lens to see if I could go beyond Grade 5 and there was very little gain to be had compared to Ilford #5; however, the output loss with 47B was severe enough to render it impractical. I also tried a 58 tri-color green to see if I could get softer than Ilford #00 and it was noticeably softer, but again the output level rendered it impractical as well. Please note that there are several Makrolons available - the one you want is Makrolon LD in B48 white. I'm guessing the LD stands for LED Diffusion. It's a new product designed specifically for diffusion of LEDs. Hope this works for you.
Jerry