Re: DIY light source for 10X10" enlarger.

"Peter Chant" <REMpeteOVE@[EMAIL PROTECTED]
> wrote

> enlarger head using LED's but a mix of
> I think blue and green were used ... Seems an odd choice to me

Blue and green are correct.  Both emulsions are sensitive to
blue light and one of the emulsions is sensitized so it will
also respond to green light.

The multi-contrast gel filters add red light for better visibility
when dodging and burning -
 red + blue = magenta
 red + green = yellow

A proper head would have red, green and blue LEDs - allowing
it to produce 'white' light for focusing and graded paper,
magenta and yellow light for VC paper, and red light for
positioning sensitive materials.

Ilford MGIV paper is a 3-emulsion paper, the third emulsion
sensitized for cyan.  For best control - especially at low
contrast grades - the head would also have cyan LEDs.

-- 
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm
n o lindan at ix dot netcom dot com