SudPigalle a écrit :
Sauf contre ordre je crois que c'est plié depuis que le dernier labo Suisse a arrêter son process
Le pb est que les colorants étaient dans la gélatine puis détruits partiellement lors du process , ce qui donnait une grande stabilité
Bonjour tristesse .....
JP
Le kodachrome est une pellicule n&b et les colorants sont ajoutés au développement qui était un procédé très complexe.
une discussion en anglais, ici ...dont un extrait suivant d'une des réponses:
"The other problem with processing Kodachrome as a B&W negative is the high contrast and dense image that results. The high contrast comes from the slide film emulsions. The high density comes from the yellow filter layer which was unique. In addition to Carey Lea silver (finely divided silver that reflected blue light) There was also a Lippmann emulsion (very small silver bromide crystals). In a B&W developer that contained a silver solvent (like sodium thiocyanate) the tiny silver bromide crystals would dissolve and develop on the metallic Carey Lea silver. The result was a dense black layer that shielded the green sensitive layer (which is also sensitive to blue light) from the blue print step.
This yellow filter layer would cause fog if an imaging emulsion came in contact with it. It was coated in the same pack as the slow magenta and fast magenta emulsions and was separated from the fast magenta by a gel spacer layer. After this pack was dried, the yellow emulsion pack was coated on top of it. If there was any mixing between this yellow emulsion layer and the slow yellow layer, it would cause some fog. The contrast of the yellow highlights could be adjusted by changing the temperature of the slow yellow emulsion at the coating step. Temperature changes also affected the widthwise uniformity so this adjustment tool was avoided. It has been 25 years since I was managing the formulas of these products, but I remember these formulas better than some of the films I designed in later years. I'm recovering from foot surgery this week and and have plenty of time to expound on this useless trivia."
Bon courage.
Posté: mercredi 16 décembre 2015 - 20:39
ne peut plus traiter...