Can you translate that for one with blonde roots?
Sorry Aggie. BTW, I had blonde roots before I was 18, but they went more reddish at that point, and a high percentage are now gray. My wife is also blonde, but she's a Ph.D. who teaches classes that require calculus, differential equations, and matrix transformations to grasp the subject properly. So even if I saw your blonde roots, I wouldn't make any assumptions.
This is a 4x5 variable contrast head that uses blue and green LEDs as a light source. It's available from Calumet and has been mentioned here on APUG. The blue and green LED arrays are controlled by separate attenuators (potentiometers/rheostats) so that their output, and consequently their relative contributions to the enlargement exposure can be nearly continuously varied. This gives the same range of results on variable contrast papers as two separate exposures with blue and green filters, commonly used in a white light enlarger for split filter printing.
It's a very cool idea (literally and figuratively), and with the recent price drops in high output green and blue LEDs, was bound to happen. I've calculated that I could get blue and green high output LEDs and circuit boards to mount them in for something less than $150. That's with half inch spacing and an array of about 99 LEDs covering 4x5 inches. That, an inexpensive power supply, a handful of resistors, a couple of potentiometers, and some diffusion plastic would duplicate the Zone VI head's function in some basic form. Add a PIC (a programmable integrated circuit used as a control device) and a little programming and you could do something home brewed that's very cool.
Lee