I'm planning on investigating the use of the Ilford ortho film soon and have done some research. Also these posts are revealing. As I understand the data, Ilford ortho has sensitivity in the violet, blue and green spectrums with some incursion into the yellow. I have used Kodak Lith film under red light with absolutely no problems. I plan to do the same with the Ilford film. I probably will not use the OC filter just to be safe.