Determine the basic exposure for palladium printing

Peter Schrager · Mar 3, 2014

my 2 cents worth..go take a workshop at Peter's Valley this summer with Tillman Crane...the best investment in Platinum printing you will ever make!
best,peter

sudek · Mar 4, 2014

Loris, I'd like to say sorry first for the questions I'm going to ask. Is "Average tool" in PS? I can't figure out which one it is. Also I don't understand how to use the levels or treshold tools to assess merging. Why not eyedropper to read K values and make comparison?

Loris Medici · Mar 4, 2014

Hi sudek. It's under Filters -> Blur -> Average. Treshold or Levels is easier to see if there's any merging step or to see which one is the darkest step - all at the same time. Do as I say (average each step - paying attention to not include the numbers and to keep the selection area always in a single step, desaturate and put a treshold or levels layer on top of the image) then fiddle a little bit and you'll instantly realize what I'm talking about.

Regards,
Loris.

sudek · Mar 5, 2014

Loris,thanks much for the detailed instruction. I scanned the 31 step tablet exposed for 40 minutes and did exactly what you've taught.When the treshold value was 43,I got step 2 and 4 turn to black simultaneously,while at the treshold value of 45,step 3,5,6 turn to black simultaneously.Is it abnormal?

Loris Medici · Mar 6, 2014

Hi Sudek, if there are more than one steps turning black with a single RGB step adjustment, then you can safely assume they're in fact merged steps, "if and only if" there aren't too obviously distinct to your naked eyes - "in natural viewing conditions". Send me (privately) the RAW scan of your step tablet print. (All of the step tablet under OHP material would be better, if you have one.)

Don't know what's going on when you further increase the blackpoint but if you don't get further merging steps we can assume that you have dmax (a convincing black) under step 5.

Can you read the number of step 5? (Makes sense only if tthe number also was under OHP.) If you can't read / differentiate the number, it can be considered dmax.

Regards,
Loris.

P.S. BTW, do the assesment always at 100% magnification.

thomnola · Mar 6, 2014

May I ask if the glass you are using has UV blockers? Could that affect not getting a full black?

Loris Medici · Mar 6, 2014

The problem is due to the fact that the process has self-masking and bronzing / solarization (when grossly overexposed). This two phenomena may lead to not being able to have any merging steps in the step tablet prints. If you're only looking for merging steps to find the dmax, that may lead you to confusion - just like sudek's case. It's simple actually; look not for merging steps (if you have them it's allright), just grossly overexpose and look for the darkest step.

sudek · Mar 8, 2014

Loris,as it seemed somewhat strange to me when I saw step 2 and 4 merged without step 3, I decided to expose for the same time to check if the result is consistent.So I exposed for 35 mins and 40 mins again,but I made new developer solution this time(I use Sodium Citrate as deveoper).And it was so astonishing......so the developer that can be used forever is only KO? It made such a big defference. On the strip exposed for 40 mins,all the steps from 2 to 8 turn into black simultaneously,which means overexposure too much,right? For the 21 step tablet exposed for 35 mins,step 4 turns to black first,followed by step 3 and 5 simultaneously,and then step 2,and later on step 6. Could step 4 be consider Dmax then? According to the calculation method you mensioned above,I should decrease exposure by approximately 2 stops,right? For a 35 minutes exposure that means about 9 minutes?

P.S. Sorry that I forgot to have all of the step tablet under OHP,covering it on the part without numbers as usual.Should I send all the RAW scans or just the newest scans? Please let me know.Many thanks !!

Peter,the suggesion is not very realistic to me,thank you though.
Thomnola,I have switched glasses before and it doesn't seem to be the problem.Thanks a lot!

Loris Medici · Mar 8, 2014

Hi sudek, can't comment about the developer; there isn't any developer in the process variant I use myself. (It's pop pd...)

As for the the evaluation; step 8 (on the 31-step tablet / 40:00 minutes test print) is dmax. Since the evaluation was made with the test film + OHP, your actual dmax is at (virtual) step 9. (You count the step tablet as 1/3 stop...) You need step 1 to be dmax, therefore you have to decrease exposure by 9 - 1 = 8 steps. With the 31-step tablet each step is 1/3 stop. Therefore, you have to decrease your exposure by 8 steps = 8 * 1/3 = 2 2/3 stops, that makes: 40 / (2^(2 2/3)) ~= 6,30 ~= 6:18 - practically 6:20. (Remember, to decrease you divide, to increase you multiply...) Seems like a pretty typical exposure time with your exposure unit and OHP...

Regards,
Loris.

Loris Medici · Mar 8, 2014

BTW, I don't see any patch beyond 8. Do you have a visual confirmation that step 9 is not dmax?

sudek · Mar 8, 2014

Loris,sorry to say that step 9 actually couldn't be seen on the tablet. I coated an area of 5X3 and torn the paper in two for the highlight and shadow steps of the 31 step tablet to save chemicals(ashamed that I've already wasted so much). I could have an integrate one for the 21 step tablet though. I'd do it again for a better judgement. Should I still expose for 40 mins?

Loris Medici · Mar 9, 2014

Sudek I'd suggest that you make the tests at final print size - or at least 8x10" if not practical. Small coating areas vs. normal or big can make quite a difference and it's hard to coat evenly at small sizes. You do not need to expose for 40 minutes for the (hopefully) last test, 20:00 would be more than enough.

Good luck,
Loris.

sudek · Mar 9, 2014

Loris,I used to coat an area of 4X5 inches which would be one of my final print sizes.When I found it made defferent when the extra water in the brush drained out,10-drops I applied before is sufficient only for 3X5 inches.I should have sticked to the size and varied the drops.The attached is the newly made strip exposed for 20 mins.The steps changed to black one by one beginning from step 2 when I applied the threshold layer.Does that mean I have no merging steps? Also I could see the boundary between OHP and the paper(I covered all of the tablet this time).Does that mean I should expose for a longer time,30 mins for example?

sudek · Mar 10, 2014

Loris,I just read the K value of each average step on the 31 step tablet exposed for 20 mins.
From step 2 to step 10, it reads as:90%,90%,89%,89%,88%,87%,85%,82%,79%.
From step 28 to step 31,it reads as: 8%,6%,5%,4%.
The paper white reads as 3%.

And for the one exposed for 40 mins before,from step 2 to step 8 all read as 83%.

If the steps have the same K value, does it mean that they're merged? And why the steps of the same K value can't turn to black simultaneously on the threshold layer?

Sorry for the childish questions. Many thanks!

Loris Medici · Mar 10, 2014

Hi sudek,

When I process the same file, I see dmax exactly at step 3. (See the attached image... Steps 2 and 3 turn black together, that means they're merged.) Since the emulsion is under step tablet + OHP and you won't have the step tablet with real prints, the dmax is at virtual step 4. (Virtual, because there's no step tablet anymore. And the UV density of the step tablet is ~1 step with the 31-step tablet. Note: 31-step tablet has log 0.1 density steps, that is 1/3 stop difference per step. The 21-step tablet has log 0.15 density steps, 1/2 stop per step.) Since you want dmax at virtual step 1 you must decrease exposure by 4 (current placement of dmax) - 1 (ideal placement of dmax) = 3 steps. That is exactly 3 x 1/3 = 1 stop. Therefore, your standard printing time should be 20:00 - 1 stop = 10:00 minutes, (VERY IMPORTANT) as long as you keep all the process parameters (formula, coating volume per area, environment, processing etc.) the same.

Hope this helps.
Regards,
Loris.

Loris Medici · Mar 10, 2014

Each K value is equivalent to 2.55 RGB value and you're experiencing rounding with the K values. Working with a desaturated RGB files gives a little bit more mathematical resolution than grayscale files.

Loris Medici · Mar 10, 2014

One more note:

With print out processes it's better to start with a little less dmax, to avoid the toe of the sensitometric curve. You'll get a little less dmax (it's fine as long as it's convincing) but much better tonal separation and detail in the shadows - right because you'll start closer to the straight portion of the curve.

So, don't fuss too much about dmax; focus on making the tonality sing. Viewers wouldn't be able to discern 1 step difference of dmax in normal viewing conditions - when the print is under glazing!

sudek · Mar 12, 2014

Loris,thanks so much for the detailed explanation.I never dreamed that I could have an exposure time as short as 10 mins.
And I just received the "magic brush" today after a long wait.I should do the test again,right?
As for the process parameters,can the temperature/relative humidity be regarded the same in certain range? It seems a bit difficult to keep them remain exactly the same.
Tons of thanks!

Loris Medici · Mar 12, 2014

Sudek, it's CRUCIAL to keep all parameters listed below UNCHANGED for the initial / calibration tests:

- Paper, (obviously)
- Formula, (obviously)
- Coating volume per area,
- Coating method, (if it's a brush, try to keep its moisture content stable too...)
- Environment, (that is: temperature and RH - small variations are OK)
- Drying method & time,
- Pre-humidification method & time (if applicable),
- Negative material, printer/inks and printer settings, (in case of digital negatives)
- Lightsource, contact frame/glass and exposure time,
- Post-humidification method & time (if applicable),
- and all of the wet processing steps.

You can relax later when making real prints. Because after awhile, you'll gain experience on how each parameter affects the end result. But for calibration, it's better to act in an obsessive-compulsive manner, in order to avoid problems / confusion later... (I'm sure you hear me about it!)

Since you're at the very beginning, I'd suggest you to start from scratch, using a test coating area / volume equal (or close) to the final print size. (I always calibrate for 8x10" print size - that's the smallest size I print...)

Good luck & regards,
Loris.

sudek · Mar 15, 2014

Loris,thanks so much for the kind suggestions.Sorry that I have questions again with the result coated by the "magic brush".

Is it abnormal that the uncovered part(neither step tablet nor OHP) on the coated paper got less density compared with the covered part? And it looks like solarization.I used 8 drops(4FO+4Pd) and 10 drops respectively and lower density on the uncovered part are the same.

And I found that if I drew different size of selection on each step,the result for the darkest or merged steps could be different,so did the K value.For example,with some size of selection,I got step 1 and 2 being the darkest and merged for the 8-drop strip.And step 1,2,4,5 the darkest and merged for the 10-drop strip.But the result may change a little bit for different size of selection.And I'm confused too on which strip I could based judgement,or neither? The TEMP/RH is about 18/60% for both strips,the previous condition (with the old brush)is about 17/64%.Does the RH variation matter? Sorry for all the trouble.

sudek · Mar 16, 2014

Loris,sorry that I just realized I should make selection according to the way you made it in your attachment.

10-drop strip: step 1,2,3,4,5 turn to black simultaneously.But the K value of step 6(85%) is the same as step 1,2,3,4,5.So the Dmax is supposed to be step 6?

8-drop strip: step 1,2 turn to black in order.But the K value of both is the same(87%).So the Dmax is supposed to be step 2?

It's so puzzling.Why are they so different? The drops are for an coated area of 4x5 inches and both of the strips are from the same piece of paper.

Loris Medici · Mar 16, 2014

Sudek, hi. Indeed with the 8d target, steps turn black in sequence. I didn't check the 10d target.

Few notes:
1. When coating volume per area changes, a very important process parameter changes. That's the reason for wildly differing results. *Use at least 0.25ml per 10 sq. in / 0.0039ml per sq. cm of coating solution*. Some papers will need a little less, some a little more, but those figures makes a very good starting point.

2. I see you still use a small area for coating, and the step tablet is very close to edges of the coating area. This is not a good practice; the edges often behave differently because coating isn't absolutely and perfectly even on the edges - definitely not a good place in a context of calibration! *Coat a larger area and keep the step step tablets at least 1-1.5" away from edges*.

3. OTOH, it's very hard to judge and mark the correct place with the standard Stouffer step tablets, because there aren't any helper marks on the negative, also the steps aren't equally sized. *I'd strongly suggest that you use Mark Nelson's tablets*. They're very nicely designed, you can discern each step very clearly because they're marked on the negative. And the numbers are readable in all steps. See the page, you'll understand why using these is considerably more productive...

4. Maybe it's time to consider a workshop; seeing a master at work will improve your grasp of the workflow immensely.

Regards,
Loris.

sudek · Mar 16, 2014

Loris,I did order a Mark Nelson's 31 step tablet last year according to your previous suggestion.I didn't receive it after waiting for more than one month.Mark Nelson said he didn't know what was going on but he was very nice and gave me full refund.And he suggested me to look for other step tablets like Stouffer.That's why I bought the Stouffer step tablets later on.

And believe me that I have no intention of insisting on coating small areas.I remember you said I should coat an area at least same as the final size print.I coated for 4X5 because that would be one of my final sizes.I would tear it into two parts(2X5 each) and placed the tablet in the middle of each part.

I'll redo it according to your suggestions of coating volume and sizes tonight.

Thanks so much for your immense patience.And sorry for all the trouble.I'm really very grateful for all your kindness and warm-hearted help

Loris Medici · Mar 17, 2014

I really don't like Stouffer's tablets. You can't discern the lower steps easily, and I just realized that in your test the steps aren't equally sized. Nevertheless use a larger area for tests, wouldn't hurt (vice versa is prone to troubles) - you need a clean and even coating to place the step tablet on. And try to be extremely consistent with tests.

Good luck & regards,
Loris.

Loris Medici · Mar 17, 2014

One more note: if you're concerned about washing precious metal down the drain, first try with traditional cyanotype. It's actually harder to get good results with traditional cyanotype (very good tool for practice / learning, and it subdues the practitioner - alot!) but it's cheap and pt/pd will be (much much) easier later. (In terms of being able to get equally good results - within limitations of each process...)

Determine the basic exposure for palladium printing

Attachments

Privacy & Transparency

Privacy & Transparency