View Full Version : Exposure times for color paper and troubleshoting

Jim C.
23-Jan-2016, 12:49
Since I'm socked in by the blizzard, I've been mucking around with RA4 print processing.
First go round I mixed the chems wrong, the resulting contact prints looked
dark reddish. I realized that I should have used the 10 liter breakdown when
I had used the 1 gallon break down, remixed correctly the second time and so far no joy.

I'm just doing color contact sheets to get accustomed to RA4 processing
my start point was no filtration ( Omega dichroic head ), high, 10 sec. and the
resulting prints look the same as with the incorrectly mixed chems,
muddy dark and reddish.

Is there a start point for exposure times and filtration any one can share ?
Any idea as to why the prints look muddy dark ?
I'm using Fuji Crystal archive paper.

23-Jan-2016, 13:31
Bad or expired chemistry?

Jim C.
23-Jan-2016, 14:23
I think the chemistry is fresh, I purchased it late last year, I've been trying different exposure times
for contact printing and I'm getting something, but nowhere near what I was expecting.

Greg Davis
23-Jan-2016, 14:36
Dark and reddish is because of no filtration. Try a starting point of 60y and 60m (never use the cyan). I found color paper to be very fast, so you may need to stop down a few stops too.

Jim C.
24-Jan-2016, 15:40
Greg, thanks for the tip, it's working a lot better now.

Drew Wiley
27-Jan-2016, 09:28
No filtration says it all. Yes, you have to watch your chemical mixing, temperature, and timing. But at least you're on the right track now.

Jim C.
27-Jan-2016, 12:25
I had initially tried it with no filtration just to see, then I tried a 40y 40M and still got that muddy red
Greg's suggestion of 60R worked much better.
What I'm confused at is how the subtraction of color works, I have a Omega D Dichroic head
and if I set the numbers to say, 60R ( 60y, 60M ) would this mean that I've subtracted 60 of each color ?

Drew Wiley
27-Jan-2016, 12:52
Not every colorhead is the same in terms of either initial color (unfiltered) or the scale of increments. So you have to fine tune according to your specific colorhead as well as specific control negative (hope you have one), your specific paper batch, and specific time/temp developer standard. Once you have that pegged down, it gets a lot easier. But with color negs, when you ADD yellow, for example, you can think of it either reducing yellow in the print, or increasing the complementary hue straight across the color wheel, namely yellow. Increasing magenta reduces magenta in the print, but increases the complement of green. The paper itself is balanced to "see through" the orange mask in the original negative, so you don't need to worry about that when using typical RA4 paper intended for optical enlargement.

Drew Wiley
27-Jan-2016, 13:10
oops.... increasing yellow on the colorhead, increases BLUE in the print. Sorry for the typo.

27-Jan-2016, 15:36
"Subtractive" and "Additive" are terms frequently applied to the colorhead control function. This function is independent of your printing process of negative to negative or positive to positive.

Drew Wiley
27-Jan-2016, 17:18
Additive heads are very rare anyway. The feedback circuitry on mine converts the control panel to ordinary YMC setting, even though the actual light itself is narrow-band RGB. But I can factor it either way. The color is more pure because there's no residual white light contamination ("spillover") like typical subtractive heads. But like ic-racer just noted, this should not be confused with the RA4 printing process itself, unless you become a schizophrenic like me, with a history of bouncing back and forth between positive and negative color printing (Cibachrome vs RA4). But that's another story for another day.