Well, I must say that I was amazed to read that yellow filtration had no effect on Ortho film. The information put out for 75 years must have been all wrong, I guess. Actually, I have found that the response of ortho film to filtration can give beautiful results. Just look in a Kodak master photoguide from the early fifties to get the exposure compensation factors needed. If you use a 2X yellow filter, you expose your 200 number to get the same negative density: e.g. 50. If you use 80 as your starting number, expose at 20 with a 2X yellow. And if you think 20 is too slow, well, that's what tripods are for. Ortho film has a tonality all it's own. I've been shooting it since 1945. I would still be shooting it in rollfilm cameras if it was available.