Customized 8x10 Codelite LED Head for Variable Contrast

**Richard Rau** · 12-Aug-2013, 21:29

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_2...p#.UgmxvnDA421

**Drew Wiley** · 13-Aug-2013, 13:44

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** · 13-Aug-2013, 14:29

Check out:

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

Great company and the owner is excellent to work with.

**Drew Wiley** · 13-Aug-2013, 15:57

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** · 13-Aug-2013, 22:50

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 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** · 13-Aug-2013, 23:33

Jerry,

What diffuser material did you use?

**cardiomac** · 14-Aug-2013, 06:13

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.