Quote Originally Posted by richard ide View Post
My reason for asking is that ortho emulsions do not excel at cloud photography.
The two reasons, that I can think of, that people use ortho films are that they like the films color response and/or they want to develop by inspection. If you add a red sensitizing dye to an ortho film you will lose both reasons to use an ortho film. If you have difficulty in rendering clouds with an ortho film why not just use an panchromatic one instead?