Platinum/palladium + a very small amt. of gold-chloride. I am using HP5 film in 4x5 and Delta 400 in 6x6. The 6x6 I enlarge on to x-ray duplicating film which is extremely slow but is a terrific reversal film. I will also enlarge the 4x5's the same way. I have made successful digital negatives from scanned film but while I have made very good prints from them they still don't match the duplicating film.