Drew; Look here: http://www.kodak.com/global/en/profe...4046/e4046.pdf and here: http://www.kodak.com/global/en/profe...4051/e4051.pdf for data on Portra and Ektar dyes. Same pages as before. You will see that there is little difference in the dyes in the two films. In fact, except for a slight edge in contrast and interimage, Ektar probably uses the same couplers (image formers) as Portra does. It is the difference in emulsions and coating design that differs between these two films and between these two and comparable Fuji negative films there is a huge gulf.