Quote Originally Posted by cnmne View Post
My experience is that the spectral output of common blue LEDs is too wide to obtain a grade 5 contrast. If you can live with grade 4 maximum, it might be fine.
Thanks for the observation. If that is the case then a supplemental #5 filter may work. In fact the Durst CLS1840 Dichro head only went to 130M and came with a supplemental Magenta filter to go to 190M.

I'll follow this progress with interest.

It still seems to me that a timer circuit is easier to build (or buy) than a PWM dimmer. So, instead of setting blue and green intensity you set blue and green time. Basically it would could be split grade printing with the push of a single button.