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  1. #31

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    Quote Originally Posted by Don M
    I'm going to weigh in on this,because I've done a fair share of VDB printing-

    It's called Van Dyke*Brown* for a reason-

    What you might be looking for is Van Dyke *Black*,which I'm not sure exists.

    Nope. I've seen well executed VDB prints too and the darker tones were actually much more darker than in my prints. You can also take a look on the VDB galleries on alternativephotography.com. When I mention "black" I'm just indicating what would be the "true black" in the VDB tone scale, which of course isn't really "black" (like 0,0,0 in RGB) but it shouldn't be that light. In fact other tones in the scale - which are indeed brown and I like them - are almost acceptable. Perhaps mine or your monitor isn't calibrated well, but if you see the previously attached scanned print to appear fine, imagine it lighter and with more flat darkest tones. Or open it with photoshop and take a look at the histogram.

    A friend of mine suggested that what I'm seeing are solarized puddles of emulsion which tend to fog the darkest tones and turn them into ligher ones. According to him, the problem might be in the chemicals or in the way I coat the paper. As for the chemicals, I don't know what could be wrong... I've used the same ferric ammonium citrate also for making my cyanotype preparate and works well there... Perhaps it is the coating or the drying. Today I'll try to let dry naturally the coated paper without accelerating with the hairdryer and see.

    Thanks for your comments

  2. #32
    Ole
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    Solarisation is different - and you'd see the darkest shadows going lighter.

    It look to me as if your negatives are simply too "short", so that the shadows are underexposed. VDB takes really, really high contrast negatives, you shouldn't expect to get good results from the same negative on cyanotype and VDB.

    I have no idea of the contrast range possible with your setup. I use only sheet film, and most of those are unable to build sufficient highlight density without resorting to staining developers.
    -- Ole Tjugen, Luddite Elitist
    Norway

  3. #33

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    Quote Originally Posted by Ole
    Solarisation is different - and you'd see the darkest shadows going lighter.
    yes, and this is a possibility

    It look to me as if your negatives are simply too "short", so that the shadows are underexposed.
    so... do you suggest that the transparency I'm using to print the digital negative produces too much fog base? But also with the Stouffer step wedge scale (which is film negative) doesn't change a thing. We're talking about blacks, the blacks are printed in the areas of the negative that are totally trasparent. I can't get more transparent than a glass! (In fact I've printed also strips of paper without anything on it and still it is too flat, no matter how long I expose... 5...10..15...20...25 minutes... there are no changes in the blacks from 6'30"; below that exposure time they can be lighter due to underexposure)

    Fulvio

  4. #34
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    What I'm saying is that on my "good" negatives, the highlights correspond to step 19 to 20 on a 21-step Stouffer step wedge while the shadows still show good detail. I notice your negative is a good deal shorter, and only about half the steps show definition - the rest are paper white?

    You should be able to expose a lot more before the shadows solarise!
    -- Ole Tjugen, Luddite Elitist
    Norway

  5. #35

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    Quote Originally Posted by Ole
    Solarisation is different - and you'd see the darkest shadows going lighter.

    It look to me as if your negatives are simply too "short", so that the shadows are underexposed. VDB takes really, really high contrast negatives, you shouldn't expect to get good results from the same negative on cyanotype and VDB.

    I have no idea of the contrast range possible with your setup. I use only sheet film, and most of those are unable to build sufficient highlight density without resorting to staining developers.
    Ole's comment about the tonal scale of your negatives being too short is essentially the same thing I said earlier, and after looking more closely at the print out of your Stouffer step tablet I think we are right. In looking at the vandyke print of your Stouffer it appears to have no more than about 11 steps printed, which would mean that your print has an exposuure scale of about 1.65, assuming that Step One is maximum black. This is much too short for vandyke, as your ES should be on the order of 2.25 or more with the classic mix. Therefore I conclude that the most likely scenario is that 1) your Stouffer step tablet is under-exposed by more than one full stop, and 2) you have probably chosen a color for your PDN system that results in two short a DR for your negative.

    Sandy

  6. #36

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    Quote Originally Posted by Ole
    What I'm saying is that on my "good" negatives, the highlights correspond to step 19 to 20 on a 21-step Stouffer step wedge while the shadows still show good detail. I notice your negative is a good deal shorter, and only about half the steps show definition - the rest are paper white?

    You should be able to expose a lot more before the shadows solarise!

    As far as I've seen I have no way to get all 21 steps printed correctly. If I expose too long, to have some color in step 20, then I have maximum black too much above step 1. On the other hand, if I want maximum black in step 1, highlights will never get enough light. If I understood PDN correctly, one needs only to find the base printing time with the Stouffer. That means, only the time required to print the maximun black tone. Once this is reached, one has to find the color which will print white with the same exposure time. The color I picked for VDB digital negatives is R=140,G=255,B=0 (but I've also reinforced the whites with a 50% multiply layer of black, with underliyng values of 125-225). Then, one has to calculate the curve that will produce all the tones between pure black and white. I did this using the table provided with PDN and the excel calculator.

    Now, in the previously posted test image, the big tone scale on the left is the result of the applied curve. The original stouffer step wedge was placed above the negative on the right of the print, just under the picture of the guy - it is not part of the digital negative, it's film and therefore doens't benefit of the curve. Also, you can't see all of the 21 steps because there wasn't much room and I placed the strip incorrectly... So only steps until 3-4 are clearly visible. Steps 2 and 1 weren't printed (which makes the whole printed step wedge useless in this case) - my fault.

    To Sandy - Thanks for your comments. Unfortunately I don't have a densitometer, but I'm realizing how useful it could be. How can I improve my PDN negatives?

    I've noticed that with Schoellershammer paper I'm getting much better results. The reason might be that Schoellershammer paper is gelatin sized, while Arches (and other paper I tried) shouldn't. This might be the important to have good results. I could size an Arches to see if there are any changes. However, I never sized a paper... Perhaps I'll open a new thread or check older threads on the topic...

    many thanks

    ciao

  7. #37

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    Quote Originally Posted by Fulvio
    As far as I've seen I have no way to get all 21 steps printed correctly. If I expose too long, to have some color in step 20, then I have maximum black too much above step 1. On the other hand, if I want maximum black in step 1, highlights will never get enough light. If I understood PDN correctly, one needs only to find the base printing time with the Stouffer. That means, only the time required to print the maximun black tone.
    ciao
    Fulvio,

    It might be better to forgot about PDN for a minute and just concentrate on printing a Stouffer step tablet in vandyke and looking at the results. That way all of use can have some common point of reference. I also use PDN but a direct printing of the step tablet is a more direct method of evaluating our exposure, mix and papers.

    So what I would ask is that you print a step tablet with the paper you hope to use. Expose the step tablet so that there is merging of maximum black at about Step #2 or #3. Then count the number of steps from the first merging to the last step that has any density. When I do this with my vandyke mix I get between 13-15 steps, which suggests a paper exposure scale of somewhere between 1.95 - 2.25. This is very typical for vandyke using the classic mix. How many steps do you get with the papers in use?

    Sandy

  8. #38

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    Thanks Sandy.

    I've adjusted exposure and developing times and concentrations (added a pinch of sodium carbonate to the fixer) and now the process works pretty well.... But I still get pleasant results only with Schoellershammer paper! I have a tonal scale that meets your description (~13-14 steps with the stouffer) and now the blacks almost satisfy me (I have still to improve coating, perhaps a glass rod will do the job a lot better). The reason why I'm not satisfied with other papers including Arches Platine could be the sizing. Schoellershammer is hard gelatin sized. In fact, also Cyanotypes are a little deeper with Schoellershammer. I don't think it is the paper that makes the difference, it must be the sizing.

    I'd like to size some paper to have a definitive answer. I have some cornstarch and also gelatin (it's not the edible kind). I'm not very sure about quantities of sizing to use... The books I have mention gelatin sizing, but I don't know if the gelatin I have is the same. The books also suggest cornstarch/arrowroot sizing, but don't tell much about dosages and mixing... Which quantities I should use? Is there a guide on how to size papers on the internet? (not specifically for photographic purposes, of course).

    Fulvio

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