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  1. #11

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    Ok, sorry, I forgot that you were having full dmax in 2 minutes - you've mentioned that in previous posts.

    The fact is that you can never reach the same dmax under the negative, more so with self masking processes, and develop out pd still has some print out, therefore some degree of self-masking. Most people aim for 90% of the dmax to calibrate for, that way you keep the dark tones more in the straight line of the H&D curve. There's always some amount of tonal progression, the trick is to find the point where the marginal utility equals 0. This is more easy to observe with a step tablet test; my method is to significantly overexpose the test tablet, then scan the print, average each step and use the threshold tool to find the minimum step number where it merges with the previous one and decrease the exposure according the numbers.

    Also, a too humid paper may compromise the negative, the silica coating is very very hygroscopic, will suck moisture and/or emulsion if it's not dry enough: try to not pre-humidify the paper or putting 1/2 mil impervious and transparent material (mylar for instance) between the paper and the negative.

    Regards,
    Loris.

  2. #12

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    sudek:

    I use three baths of (4 heaping tbsp EDTA & 2 heaping tbsp of sodium sulfite per gallon) and get complete clearing - I no longer use citric acid at all & end up with the paper being the same color with no yellow stain left.

    Loris already covered my next comment: the Pictorico coating is water-soluble.

  3. #13

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    BTW, when not using a step tablet, you have to calculate the exposure individually for each step so that each one takes the same amount of "logarithmic" exposure, see below:

    1. Target total test exposure time: 10minutes,
    2. Each step: 1/3 stop, (pick your own values for these)

    then

    10:00 (start timer, none of the steps are covered)
    07:56 (cover the first step)
    06:18 (cover the second step)
    05:00 (so on...)
    03:58
    03:08
    02:30
    01:58
    01:34
    01:15
    01:00 (cover the 10th step, there should be one more step remaining, that will be exposed for the last minute...)

    To find the correct slices for a different total exposure and/or step resolution you can use the formulas below:

    1. To increase: time * (2 ^ (step)),
    2. To decrease: time / (2 ^ (step))

    Example:
    1. 10:00 + 1/3 stop = 10 * (2 ^ (1 / 3)) = 12,60 = 12:36,
    2. 10:00 - 1/3 stop = 10 / (2 ^ (1 / 3)) = 7,94 = 07:56

    Since that's a real PITA (both calculating and waiting before the exposure unit for an impractical and dangerous duration - UVA is not good for skin and eyes!!!), most people prefer using step tablets.

    Regards,
    Loris.

  4. #14

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    Richardk550,

    Thanks much for the clearing experience


    Loris,

    Thanks a lot! Ok, I'll get a step tablet and have a try,but I'm wondering how I could make it in a few minutes with the step tablet while the blank pictorico itself couldn't get dark in more than two hours.

  5. #15

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    Hi sudek, try not-humidifiying the paper and putting 1 or 2 mil (25-50um) thin clear polyester between the coated paper and negative first. This became my standard practice after ruining a couple of negatives. The step tablet comes later when you figure out what happens right now.

    Edit: BTW, I reading again I see I've made a mistake, you don't cover the steps as I described above, you open them, I wrote the other way around above. You expose the first step 1 minute then open each step on each stated time. You must use a chronometer not timer (which counts backwards). Sorry for the inconvenience, it's long time I didn't it that way; step tablets makes people lazy! BTW, one plus of step tablets is that you have the same base for comparison with other tests and tests of other people...

    Good luck,
    Loris.
    Last edited by Loris Medici; 10-02-2013 at 05:14 PM. Click to view previous post history.

  6. #16
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    With the name of Sudek, may I ask what you think of your Sudek's work?

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  7. #17
    cliveh's Avatar
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    Apologies for my last post, which doesn't make sense. What I meant to say was with a name like Sudek, what do you think of the work by josef Sudek?

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  8. #18

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    Loris,thank you very much! I'll post the result later.

    cliveh,it's fine. I didn't feel offended. I like much his sensative and poetic way of seeing things. And above all, it's his great passion for photography and life that's impressive. I can't imagine how to operate a large format camera with just one hand and it's the left one.

    BTW, I adore much the works of his compatriot Josef Koudelka. The list of the photographers I love is very long: Hiroshi Sugimoto, Sally Mann, Richard Avedon, Ivring Penn, Eikoh Hosoe, Michael Kenna, André Kertész, H.C.Bresson,Sarah Moon, Paul Caponigro and many more...

  9. #19

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    I just got back to the experiment.

    Light: a bank of 8 30W HITACHI tubes about 4.5 inches above the print (the tubes are newly changed)
    Paper: Bergger COT-320
    a 21 steps tablet(I couldn't get the 31 steps tablet locally),half of which covered by Pictorico Ultra Premium OHP Transparency Film

    I exposed for 20 minutes and 40 minutes respectively, but the steps are all far from black,yes,even the part not covered by OHP film. Then I changed the glass from 5mm to 2mm and exposed for 40 minutes.Same result.

    Frankly speaking, it's making me feel despair. How come you can make it in just few minutes? I have no idea what I've done wrong. What should I do? To expose for two hours is not a good idea,right? I understand too long exposure is not right for making palladium prints.

  10. #20

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    Click image for larger version. 

Name:	step tablet.jpg 
Views:	54 
Size:	59.5 KB 
ID:	78297

    The attached is the one exposed for 40 minutes with the 2mm glass.

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