Quote Originally Posted by Nicholas Lindan View Post

Split toning is caused by the two (or three) emulsions that make up VC paper reacting to selenium in a different fashion. Where in the tonal range the split occurs and the severity of the split changes with changes in contrast filtration. Modern papers that are sold as 'fixed grade' are often crypto-VC papers made with two emulsions with different fixed sensitivities. The "black circle/white box" Oriental paper had a noticeable steep spot in the HD curve where the curves of the constituent emulsions overlapped. See the application note on the DA web site http://www.darkroomautomation.com/su...vcworkings.pdf for more on VC paper.

The late Forte Polywarmtone paper had the most outrageous split toning. Dark tones went a chocolate brown while light tones were completely unaffected. Although chemistry and phases of the moon can affect split toning, the paper seems to play a large role. Apart from pathologies like Forte, I have never had split toning problems to this degree before.

Most emulsions from major manufactureres are blends whether films or papers and have been for many years, I wouldn;t take too much account of what's written on sites like DarkrooAutomation.

Many people want the split toning ability, it's not a fault it's an attribute to expoloit or suppress. As I said previously Thomas Joshua Cooper exploits it to its full as did another American photographer Olivia Parker, both achieving exquisite results.

Having seen that the effects of the green tinge is greater with very fresh emulsions on a few occasions now I have to contradict Simon & Bob here, a lot depends though on how you handle a papers with regards to exposure and development time and you can loose almost eliminate it but varying exposure/development time.