Tweaking with QTR

[PVia]

Hi everyone,

I've been making pt/pd prints in the sun for a long time with wonderful results. Now that I have a NuArc I have needed to make some tweaks mostly in order to bring exposure time down. My sun exposures have been 7 1/2 - 8 minutes and with the NuArc they have been around 24 minutes. I have used a curve to get my time down to 12 minutes, but it's a pretty drastic adjustment, nothing that shows strangeness on the neg or print, but it seems heavy to me.

Is there a way to bring the density down (without affecting my contrast relationship) in QTR and without altering the rest of the relationships within my QTR printing profile?

IOW, the prints at 24 minutes look fine, but can I bring that printing time down linearly, keeping everything else the same.

Just pondering this...

 

[Ron-san]

Man, that is not a tweak, it is a bludgeon you are asking for. My Nuarc (an F26 fliptop) only needs 3 min 40 sec for a basic palladium printing exposure. Sadly I do not know of any fool proof method to do what you wish. Be sure you have your basic exposure correct (minimum amount of exposure needed to print maximum black through clear transparency material). Then turn off Gray Curve in your profile. Then try lowering the dark ink limits until you just get pure white in the 0% step of the step tablet. Then (and here is where I am only guessing) try lowering the light ink limits by the same percentage you had to lower the dark ink limits. If this looks hopeful (if it makes a step tablet print where you can see some tonal separation between about 85% and 100%) you can turn the gray curve back on and see if it will still linearize the midtones. If it cannot, you will have to throw it away and derive another gray curve. Don't you just love printing step tablets?
Let us know if any of this helps. Cheers, Ron Reedeer

 

[Loris Medici]

I don't get all this; what's the relation between the curve and exposure time? Those two are completely different issues; the exposure time is determined according to the combination of the following: lightsource, emulsion, negative material's b+f, paper and (finally) humidity. It has nothing to do with the tonal structure of the negative; you don't calibrate the exposure time according to the dmax of your negative, you calibrate it according to the dmin, then tailor the negative DR/contast (and tonal structure, especially in case of digital negatives) according to it...

 

[Ron-san]

Loris-- In QTR the values of the midtones are determined partly the ink limits you impose on both the dark and light inks as well as by a Photoshop correction curve that is also applied to the ink settings. The problem, as I understand it, is how to lower the ink limits (he apparently has a negative that is way too dense) without altering the midtones relationships. I frankly doubt it can be done without simply remaking the entire profile, but maybe he will do the experiment. Cheers, Ron Reeder

 

[Loris Medici]

Thanks Ron, but still doesn't make sense to me... In the context of digital negatives, the curve (or any other tweakings done in a RIP) doesn't have anything to do with the correct exposure time; those two are completely different / separate issues. In an ideal workflow, the correct exposure time is absolutely independent of what you put on the transparency, and how...

Regards,
Loris.