BTW I have his LED lamphouse for my D2V condenser head and it's a very well made piece of gear that works great. Not sure if I posted the scans here of the comparison I did for evenness with the incandescent lamphouse but I know I posted them on APUG.
My Flickr page
Most blest is he who lives free and bold
and nurses never a grief,
for the fearful man is dismayed by aught,
and the mean one mourns over giving.
- Hávamál verse 48
Most people looking for one of these units I suspect would be fabricating their own adapters. An adapter isn't what I'm looking for, just the light source boxed head unit. "Universal" light source.
I started and ended the Aristo project too. Now I'm finishing a three halogen bulb with dichroic filter diffused light head for a Durst 5x7. if I knew an LED head was available I would buy one instead.
On my beseler cb7, I can't easily read the numbers on the contrast dial when it's higher than 8x10 print size. It's up high! If you can put it on the head, aiming the controls down a little would be better than straight ahead. Having the control in a separate box is more clutter on the work area and one more thing to keep paper away from if it's got illumination.
I'm fine with individual brightness controls, but either arrangement is workable. A simple chart could be made afterwards to show what combinations to use as actual contrast could vary depending on the spectral sensitivity of the paper choices.
What I'd really want (and would pay extra for) would be a serial (perhaps via 1wire) or USB input where I could computer control it by sending a simple command (such as 3 floating numbers) over the wire like x% green intensity, x%blue intensity, 14 second, and it would do that. Sort of bring it into the 21st century. our own Apps that operate the enlarger would also log settings so we don't have to, perhaps use a webcam for an exposure meter, etc...
www.deadbread.com/crumbs/23c.html) and I'd like to share some observations from my own testing of blue and green LEDs last year:
Despite appearances blue LEDs aren't a "pure" blue. To the eye they are strong vibrant blue color, but they're actually a combination of blue and green. I observed this with a homemade spectrometer and with VC paper printing tests. This is important as blue LEDs (with the inherent slight green bias) by themselves just won't allow for the maximum hard contrast grades. For the best results you'll need to use a blue LED without any green hidden in its spectrum.
Second, the sensitivity of VC paper changes drastically with the color of the light. Green takes a a fair amount time to expose paper fully. Blue takes but fractions of a second. Variable contrast paper does not have an even response to the two colors of light. Adjusting the amount of blue and green will also have the added headache of simultaneously changing the basic print exposure time.
Ilford (and once upon a time, Kodak) solved this for variable contrast paper with their VC printing filters by building in varying amounts of neutral density into each filter. Every filter has slightly different amounts of neutral density so in use when a #2 is replaced with a #3, the underlying basic exposure for the paper is still the same.
Food for thought.
Just my random thoughts -
Didn't Calumet try to market an LED head a few years ago with built in VC controls? As I recall it was very expensive and didn't sell very well. My input would be to keep it simple and let the old VC filter system do the hard work, while you just work on changing the light source to retrofit into enlargers - at a reasonable price. I think a fairly large number of current users would be interested in upgrading.
Exciting stuff, wouldn't you agree?
This is a follow-up to my last post. I ran some test prints tonight using my Omega diffusion housing with four Cree XP-E Royal Blue (450nM) LED's driven at 900 mA. Scans of the prints are attached. The first print is just pure blue light with no filtration. Exposure was 10 seconds at f11 on 8x10 Ilford MGIV paper developed in Dektol for 2 minutes. About five steps are needed to go from black to white with the 21 step tablet. This is about a contrast grade 4 to 4 1/2. Brightness is excellent and about 2 full stops brighter than a 150W incandescent bulb in a condenser housing.
The second print was exposed the same as the first but a #5 Ilford filter was placed below the lens. About 4 steps are counted in this print, or about contrast Grade 5. The filter cuts the brightness by at least a full stop.
By way of comparison, white LED's with a Grade 5 filter yield about 3 1/2 steps.
So the conclusion is that the Cree Royal Blue LED's are capable of producing fairly high contrast but not the maximum contrast the paper is capable of. The addition of a Grade 5 VC filter improves the contrast slightly but at the expense of significant printing speed.
In practice, I think a maximum native contrast of Grade 4 is sufficient for most purposes. For those rare occasions when a grade 5 is absolutely necessary, a #5 under-the-lens filter can be added with appropriate exposure compensation.