http://www.google.com/patents?id=Hwx...page&q&f=false

This is interesting 1922 Kodak Two Color Photography Movie Film patent.

It is very interesting because if you look closely , you will see the two sided , two emulsion film and the surfaces are not flat

but gelatine relief

like gelatine alt printing method or tiffdruck rotogravure cylinders as used as printing of National Geographic Magazine.

They are two three dimensional surfaces and there is huge difference at rendering tones and printing strong colors.

Best ,

Mustafa Umut Sarac

Istanbul