DIY LED Enlarger head for D2

[Ulophot]

Here are some images of the LED head and timer/controller that a friend up the street built for me, using a 3-D printer and his knowledge of electronics and coding. He is not a photographer, so I specified what was needed and we worked out details. I work in B&W only and needed a new head to replace my dying coldlight head (I suspect there are quite a few of those out there; lamps for some can still be purchased but at a premium, and the rest of the "innards" will not last forever) and LED seemed clearly the way to go. Except, that I'm hopeless at building things and don't have the money to invest in a Rolls-Royce model like the Heiland.

This one is not as bright as those made from individual, larger white or other LEDs, but it's adequate, fairly close to what I got from my coldlight. It uses a 6x6-inch 256-LED RGB panel, which I adjusted to give white light of equivalent color to a tungsten bulb, hence Gr. 2 with my Ilford contrast filters. The panel idea came from a design offered in full detail by a poster using the name elgatosuizo over at largeformatphotography.info a couple of years ago, but my friend made many changes, including the coding language for the Arduino computer in the controller. The head incorporates the power supply; the fan (see top view) -- a relatively low-RPM computer case fan -- is vibration-free and extremely quiet.

The controller's two dials each perform multiple roles. The left one adjusts the exposure time in 500ths of a second (half a tenth) and goes up to 59 seconds. "Click on" the dial successive times to adjust, individually, the red, green, blue, and the overall intensity, then return to time adjustment. Push the right-hand dial to turn on the light for focusing; push again for off. In the off position, turning the dial adjusts the dry-down percentage subtracted from the exposure time, from 0 to 15%.

Light evenness gave us some headaches, with edge falloff accentuated by my 135mm, rather 150mm lens for 4x5. This was solved by an Excel program offered by another member over yonder, allowing adjustment of intensity of consecutive rectangles of LEDs, from the outside, in. Some playing around with this optimized evenness and overall intensity.

I had to add lead ingots weighing a total of about 6-7 lbs to counter the powerful band-springs that raise the head.

 

[albada]

Your friend did beautiful work. You're fortunate to have such a talented and careful friend.

You might consider changing green and blue to achieve each contrast, and then eliminate the contrast filters. In fact, you could put grade-presets into the controller, consisting of a green-blue for each grade, which you could select with a knob. Just an idea.

Anyway, congratulations again. I think you'll enjoy using this LED-head.

Mark

 

[Ulophot]

Hi, Mark. Thanks for the thought. For a couple of reasons I chose to continue using the filters.

First, from the time I started posting prospectively about such a head several years ago, my idea was for a "plain vanilla" design that could potentially be adapted to a number of different enlarger configurations. I thought that someone could develop a two-stage or two-module (upper and lower) design, the lower holding the light source and the upper the adapter part. (I believe that the Heiland does exactly that, though I didn't know about it at the time.) By keeping to white light, the cost could be kept affordable for people like myself. Based on cost of materials, I was figuring that someone with the skills and tools, perhaps a reitred person, could sell on a small scale and make a reasonable profit, to the benefit of many.

Second, I have been using the filter system since the 1960s and am comfortable with it. A controller with presets would be nice, but that would have been beyond the scope of this project, My friend imagined it to be a weekend's work(!); it turned into a year, with a wide variety of problems cropping up along the way of our part-time attention to it. I had initially suggested individual green and Royal Blue LEDs in a suitable array, as tested by other builders, but my friend did not wish to deal with all the included issues involved, and I was just paying for materials.

If I were ever get a chance at another design, I would go with individual LEDs, although simple white ones would be perfectly adequate and simpler, as done linked below. A G-B array and controller with presets would be icing on the cake, but I'm very happy with the one I have.

 

[Xylo]

Wow, that is a pretty involved build. Much more sophisticated than mine as I just replaced the PH212 that was in it with a warm white 100W equivalent LED bulb

 

[Ulophot]

Hi, Xylo. Sorry for delayed response. Your alternative would probably have been my choice, had I not already sold the lamp housing of my D2. After I got the coldlight head originally, back in the late '90s, I was delighted with it, so I eventually sold the housing and condenser lenses, keeping only the collar and the mid-section of the head.

 

[Xylo]

I must admit that the LED strips are definitely a better solution than a cold head. While those tubes work great, for me the cost was always a concern.

 

[redbandit]

but one has to ask.. does it replace or out do ye old ph111 and some contrast filters

 

[Xylo]

but one has to ask.. does it replace or out do ye old ph111 and some contrast filters

I must admit that changing from a PH-111 bulb will require changing the socket. But if a modern LED bulb can be fitted, it's well worth the effort.
If you use a warm white bulb in any enlarger, it will work just like before without any significant change to the color grades. As a bonus, you won't cook the negatives anymore and it completely eliminates negative pop.