C41: the standard process for color negative film - Kodak Gold, Portra, Fujifilm color negatives.

E6: for reversal (slide) film, which develops into a positive you can view directly on a light table - Ektachrome, Provia, Velvia.

B&W: black-and-white negative development - HP5 Plus, Tri-X, Delta, ACROS. B&W reversal is a separate, special process.

ECN-2: for cinema color negative stocks like Kodak VISION3 (500T, 250D). The chemistry differs from C41 and the remjet backing must be removed.

When in doubt, check the box or cassette for "Process C-41" / "E-6" markings - or just write the film name in the order notes and we will identify it for you.