Quote Originally Posted by Paul Ewins View Post
Would this be usable with VC papers? Do white LEDs have enough of the spectrum to enable the use of traditional VC filters?
Quote Originally Posted by Steve Smith View Post
I think you are right, you will push it towards harder or softer grades but I don't think you will get near to grade 0 or 4. I think my blue and green LEDs give me about 1.5 to 3.5 at most. I wouldn't expect even that range with filtered white LEDs but I wouldn't mind being proved wrong!
Yes, white LEDs work fine for VC paper. I've built two 4x5 enlarger heads from scratch using white LEDs as the light source. The spectrum of white LEDs is continuous for the entire visible spectrum; however there is a very small gap in the blue portion. I checked this visually with a homemade spectrometer.

I also ran practical printing tests with a Stouffer 21-step print wedge. I compared white LEDs to regular tungsten and florescent 'cold' lights, with and without VC filters. In all cases the white LEDs worked well, and I was able to reach any of the print grades from -1 to 5+ with white LEDs. Individual blue and green LEDs alone are a different story.