Exposure TImes and Black Point

PiezoDN Digital Negatives
1

Hi - I have a basic question. Is there a surefire workflow for determining exposure times? I am making negs for Pt/Pd using a curve from Pro inks, and I am not sure if I am giving my negs enough exposure. My images are too light, so I ran a 16x21 patch neg and made a print. The lighter values are too light. Before I get into a long process of measurements and curve alterations, I am wondering if I am also just not exposing my negs for long enough. The black on my print seems good to the eye, and if I reduce my exposure time, it does not change. But is there a way to test if I have gone far enough on my exposures.

I am using a NuArc expusre unit built for screen printing, and exposing for about 15 minutes using 50/50 pt/pd in the MaldeWare process.

2

Because Malde-Ware is a print-out process it will not reverse like dev-out. You can safely increase your exposure time. But also you may simply want to tune your curve to be darker and then linearize it.

PiezoDN instructions: https://shop.inkjetmall.com/piezodn-and-the-digital-negative (scroll to the “Custom Tuning” part)

best,
Walker

3

Also sounds like you are asking about how to do a base exposure test. If so, I hope this helps, which is a short extract from my upcoming book, “Platinotype: Making Photographs in Platinum and Palladium with the Contemporary Printing-out Process”:

  1. Sensitize and hydrate a sheet of paper
  2. Lay a clear piece of your standard film (UP OHP Pictorico ) across two-thirds of sensitized area, close the printing frame
  3. Place opaque board, ideally 4-ply black mat board, across both portions of the sensitized area, then uncover about 20% of the area
  4. Make a series of 2-minute or 100-dose exposures by uncovering in 20% increments
  5. Process and dry the print
  6. Base exposure is indicated by the darkest step after which no further change can be discerned between the areas covered and not covered by film
  7. Repeat test, reducing or extending exposures, to fine tune if necessary
2 Likes
4

Thanks - that was very helpful.

I had always been trying to get my exposure so that the black under the OHP film was as dense as the black with no film. I could never manage to do it, even at very long exposure times.

I realise that I have, in fact, been using too long exposure times, rather than too short.

5

Dera Walter,

Thank you. I actually have the Pro inkset. Can I use the workflow to calibrate/linearize the curve as you describe in this video?

I have been using this workflow instead of the Piezo DN workflow that you described in your reply.

6

PPEv2 can be used yes.

-Walker

7

Walker, I am going to test Malde-Ware and since I’ve not done printing out processes before I am wondering what is the recommended way to determine the minimum exposure for maximum density. Pradip’s description above for determining base exposure seems very similar (identical?) to the way Keith described it in this post (and the way I’ve been doing it for “traditional” develop-out Pt. / Pd.): Can I use 129 step target to calculate print times??

thanks,
Michael