Re: Exposure times in tricolor gum
Yes, the Y curve is quite a lot closer to the 45 degree line - less sigmoid than the cyan and magenta curves, which are close to identical. Afraid I mix the pigment by eye - small blob, larger blob... So can't be of much help there. Best wishes Henry On 18/11/08 12:50, "Loris Medici" <mail@loris.medici.name> wrote: > Thanks Henry, > > By "...Y is much flatter..." you mean that it's closer to the ideal 45 > degrees linear transfer function or it's more drastic? I'm currently > printing using a single curve devised from M tests. > > What can you say about the pigment concentrations you use? > > Regards, > Loris. > > > 18 Kasım 2008, Salı, 2:43 pm tarihinde, Henry Rattle yazmış: >> Hi Loris, >> >> My exposure times (50% gum/pigment, 50% saturated Potassium dichromate) >> are >> 7 minutes for C and M, 10 minutes for Y. These times are "standard >> printing >> times" from precision digital negatives (PDN) testing, all exposed through >> R255B60 colorised negatives, with separate curves generated for each >> colour. >> (The C and M curves are very similar to each other, the Y is much >> flatter.) >> >> Best wishes >> >> Henry >> >> >> On 18/11/08 12:20, "Loris Medici" <mail@loris.medici.name> wrote: >> >>> This goes mainly to tricolor gum printers printing from digital >>> negatives >>> separately calibrated for each color layer: do you experience any >>> exposure >>> time variation? If yes, can you please tell me your exposure times (and >>> dichromate strenght, only if it isn't kept constant) for each layer? I >>> just want to see if there's a correlation / connection... >>> >>> I balanced the pigments according to 2Y + 1M + 1C. In other words, my Y >>> stock paint:gum solution contains 2x paint compared to both M and C >>> solutions. Using the same coating solution formulation (which is 1 part >>> paint:gum solution + 1 part gum solution + 2 parts 10% ammonium >>> dichromate >>> solution), I find that yellow requires the most exposure whereas C >>> requires the less (M in between). Is this similar in your case? >>> >>> Thanks in advance, >>> Loris. >>> >> >> >> > >
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