Customized 8x10 Codelite LED Head for Variable Contrast

[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/dis...nav_id=9,0,0,0

Material properties: http://www.sheffieldplastics.com/web.../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.

[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.