Ziatype Calibration for Digital Negatives

Discussion in 'Digital Negatives' started by Janosch Simon, Sep 19, 2017.

  1. Janosch Simon

    Janosch Simon Member

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    Hey all :smile: after some trouble with old chemistry i mixed my own new and now it works better but the Calibration drives me nuts :D. i got the great book from peter Mrhar "Easy digital negativs" and like his approch wich breaks roughly down like this:

    1. find exposure time for maximum Black
    2. find best blockingcolor for your printer ( you can find the HSB grid and other files used for the calibration here: http://www.petermrhar.com/downloads/ )
    3. print the EasyDigitalNegatives-StepWedge-256-HSB with the found blockingcolor applied.

    and here stars my problem :D
    the highlight area looks not smoth more like gritty and ugly
    dave j smith has some nice videos which show the calibration proces he uses the platine/palladium process
    https://www.youtube.com/user/macgabhan and when you look at his step wedge even the highlight patches are smooth GRRR.
    very complex but perhabs someone else uses the Peter Mrhar calibration and has an idea?

    the printer i use is an Canon ipF 605 paper Hanemühle platinum rag which is humidifid in a humidity box with saturated salt solution(75% for one h) exposure is done with an diy UV lamp.

    any feedback welcome :smile:
    cheers janosch
     
  2. ced

    ced Member

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    Hello! I have been trying PM's system recently & the thing I love the most is the combination of two curves into one via an aggregate calculation (wish I knew how to do this in Pshop).
    I am interested in gumprints which I gave up because the highlight areas were too broken up to get a decent measurement so went to cyanotype and did the whole calibration there which was much better as far as smoothness goes in the highlight area.
    Then I took the curve to gumprint with an adjustment (1/5+/-) less exposure and think this is the best way for me to continue. What is interesting is that the system does work as the anticipated curve arrived at from PM was approx. the same as arrived at manually (lots of fiddling whereas here only three to four passes were needed). I did smooth out the results from each calculation before combining and that result too I gave a small adjustment to tidy up the shape of the curve whether this is absolutely needed I am not sure but I sleep better. Good luck it is a great system & would reccomend it to anyone needing a method to calibrate.
     
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    Janosch Simon

    Janosch Simon Member

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    hey ced :smile: i dont use the curve method i prever the gradient method :smile: but first need to solve my problems GRRR :D

    cheers janosch
     
  4. nmp

    nmp Member
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    Hi, Janosch:

    If you could post some pictures, it will help diagnosing what the problem is.

    :Niranjan.
     
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    Janosch Simon

    Janosch Simon Member

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    IMG_2118.JPG sure thing just a handy snap it shows that my blocking color is wrong and the light patches are ugly :sad:
     
  6. nmp

    nmp Member
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    So looking at the picture....

    I am thinking that may be there are two separate (or perhaps compounded) issues here. One may be the digital negative itself and the other related to the process (paper, coating, developing and clearing.) If you only had a less-than-optimal color for the negative that was not opaque enough at the highest values, you should still have smooth blocks and not blotchy or rough as you see here. You can see this structure not only in the highlight areas but in the darker mid-tone zones as well.

    Did you do any step wedge printing to get to the standard printing time. If so how did it look in the lower exposure steps?

    :Niranjan.
     
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    Janosch Simon

    Janosch Simon Member

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    standard printing time i did with a method from peter mrhar very easy and there you cant see the problem cause the blacks are smooth :D and as for the process itsself im pretty confident that coating developing is not the problem im affraid its the dye ink of the canon ipf 605 i will make a test with a diffent color method then the last tries and then see if this gets better or worse :smile:
    cheers janosch
     
  8. Prof_Pixel

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    Janosch Simon

    Janosch Simon Member

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    made another test and the patches look much better i have 3 solutions:
    Ammonium Ferric Oxalate sol.A
    Ammonium Ferric Oxalate contrast sol.B
    Lithium Chloropalladate sol.C

    all test bevore i made with a 4 b 2 and c 6 drops
    today test i left b away so 6 drops a and 6 drops c
    and oh wonder the patches are better but the blockingcolor is useless so tomorrow i make the hsl grid again without contrast thing GRRR :D
     
  10. ced

    ced Member

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  11. DennyS

    DennyS Member

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    The sulfamic acid treatment is useful for papers that require acidification, but Hanemuhle Platinum rag does not need any acidification. It does coat a little easier if you add a small amount of tween to the coating mix, maybe not necessary with the extended humidification in this case.
     
  12. nmp

    nmp Member
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    If you are making diginegs from scratch, I am of the opinion that it is best to leave the contrast agent out, in general. It is more useful if you already have a negative and want to fine tune the contrast like using different grade papers in silver gelatin printing.

    Good luck!
     
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    Janosch Simon

    Janosch Simon Member

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    thx guys today i will check for new exposure time and make a new hsb grid test with the new time i also test a cheap transparent foil from german ebay seller vs pictorico ultra to my eye they look the same but the foil from ebay is much cheaper :smile: Dead Link Removed will report back with the result :smile: cheers janosch
     
  14. nmp

    nmp Member
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    Sounds like a plan. Please keep us posted. I am particularly interested in the alternative foil. I am struggling with the Pictorico Ultra myself currently.
     
  15. Richard Boutwell

    Richard Boutwell Member

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    "Easy Digital Negatives" is an unfortunate and misleading name for it.

    If you are using an Epson with UCK3 inks you might want to check out my QTR QuickCurve system. I personally think trying to use a color blocking target and doing an extreme correction with PS Curves or LUTs or Gradient Maps is the wrong way to go and should be avoided if possible. Aside from the number of variables in the color driver, the main downside is that you are using very few of the available inks in the printer and it can cause that graininess you are seeing. The other huge problem is the extreme tonal correction applied to the image rather than doing it with actual ink levels.

    If you REALLY want to make it easy, take a look at my system: Dead Link Removed
     
  16. jim10219

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    One problem I ran into with using a color other than black (or straight cyan, magenta, or yellow) for your negatives is getting the printer to print consistently with that color. I can't even get Photoshop to gradate the colors accurately using the correct ratios (as confirmed by the eyedropper tool).

    What I mean is, if you take a 100 block grid going from 1%-100% in 1% increments trying to print using lets say 100%C, 100&M, 0%Y, and 0%K as your 100% UV blocker, PS will try to make your 50% block something like 65%C, 43%M, 11%Y, and 7%K. So basically everything else in between 100% and 1% will be screwed up. Even if you switch it over to a duotone and print it, the printer drivers won't balance them out correctly, and you'll get what looks fine to the naked eye, but won't print accurately and smoothly like it's supposed to. A spectrometer or loupe will reveal that it's color transitions aren't as smooth as they appear, and your prints will reflect that.

    The only way I've found to get an accurate and smooth gradient grid, is to use either black, cyan, magenta, or yellow as your color. Between those four, I've found black to be the best, and using the "print grayscale" option ensures that I'm not getting weird mixes of colors that will give me inconsistent results. Plus, with the 100%C, 100%M ink combination (done as a grid in Illustrator where you can have more control over the colors), I was getting exposure times into the hours (for cyanotypes, Van Dykes, and gum bichromates) before anything above 50% ink coverage would start to expose. So while I was theoretically getting more UV block out, I was getting less usable range. When I switched to all black, my exposure times were closer to 2-4 minutes, and the tonal range I was able to achieve was much longer.

    I'm not sure if I'm doing something wrong. The instructions that I've found online are never all that clear (to me), and none seem to address my issue (that I've seen). But my system works well enough that I've decided to stick with it unless someone can enlighten me as to a reason why I should switch.
     
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    Janosch Simon

    Janosch Simon Member

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    hey richard nice to meet you here we are "friends" over at facebook :smile: lee uses your systm right? his ziatype are amazing might come back to you at the moment i dont own a printer use the one i have at work :smile:

    cheers janosch
     
  18. Richard Boutwell

    Richard Boutwell Member

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    The "problem" with using the color driver is how it uses a mix of the CYM inks to generate gradations along with the K,LK,LLK inks. there is a lot of gray underpainting and color mixing the driver does that isn't ideal for negatives. I have looked into it for creating my own system for another application but put it aside for the time being.
     
  19. Dan Pavel

    Dan Pavel Member
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    I've tried many "calibration" methods for the alternative processes and none of them gave good results in any situation. Most of the time you have to re-trace the curves in PS and make more tests to get a good result. I ended-up with the conclusion that the process of "calibration" itself must be, somehow, wrong or incomplete. Calibration tries to map an extended scale of equidistant grays into one with the same number of grays that keeps the equidistance while respecting the Dmax and the Dmin capabilities of the alternative process/paper involved. Simply saying the "calibration" is a method to compress a gray-scale into another gray-scale keeping the relationships between the grays. At first look it seams a correct approche and mathematically it is, undoubtedly, correct.

    But...
    As many have noticed it doesn't always lead to good results. Why? IMO, the "Calibration" method is a compressing method very similar with the DOLBY sistem in music (the compress of an extended scale of frequencies to meet the limited recording capabilities of the magnetic tape) with an essential difference - when you play the tape the DOLBY system expands back the scale of frequencies and the sound is perceived correctly. This final stage is completely absent in the Digital Negative "Calibration" methods. It is like playing a DOLBY-recorded tape on a non-DOLBY device - the result is somehow flat, un-natural. That's why the existing "Calibration" methods lead to better results if you start with an image with higher contrast.
    The mathematical correctness and the process automation can't automatically lead to a perceptual correct result. In music, on a non-DOLBY device a tape recorded without DOLBY sounds better than one recorded with DOLBY. That's because the frequencies are specially adjusted in studio to meet the tape capabilities - not by trying to to record them all (impossible on tape) but by restricting to the ones that ca be recorded on the specific tape and by changing the relation between them in order to make the music sound natural. In Architecture the proportions and straight lines of the Parthenon have had to be altered in order to look correct. If they were kept correct they wouldn't look correct. It's a general principle in Arts - things must LOOK RIGHT and not necessary BE RIGHT, contrary to science/engineering. The same should be true in making a Digital Negative for the Alternative Processes. IMO, a completely different, perceptual approach is necessary.

    In the last months I have worked at developing the work-flow of such an "perceptual" approach in the creation of the Digital Negatives. It's now in the extended testing stage and, at least for me, it works better and it's more predictable than the traditional ones.
     
    Last edited: Sep 21, 2017
  20. nmp

    nmp Member
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    Dan:

    Excellent analysis......you put your finger on the crux of the matter that I have not seen being talked about in discussing various methodologies.

    I too noticed this flattening of the image soon as I made my first POP print, to my great disappointment, even though I thought I had done a good job of figuring out the correction curve as well the other parameters of the digital negative. Not being much of an audiophile, I didn't make the analogy with Dolby. However, it is easy to see on Photoshop what would happen if you take an image and apply ideal curve taking into account the Dmax and Dmin of the process. To counter this, what i did do was to apply a contrast curve to the original image, my perceptual approach if you will, before the whole process of correction curve, flip, invert and colorize. And the results were much better, felt in perception nearly as good as the original image. I think we can discuss this on another thread as obviously this becomes an all together different subject.

    :Niranjan.
     
    Last edited: Sep 21, 2017
  21. Dan Pavel

    Dan Pavel Member
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    OK Niranjan, I'll open a new thread on the matter.
     
    Last edited: Sep 21, 2017
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    Janosch Simon

    Janosch Simon Member

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    very nice discussion :smile:
    so here are some news in regards to the foil i linked i measured it and with same print setting i get dmax for the cheap one of 1.67 and 1.77 on the pictorio as i dont have a color measur device the two prints look to my eyes on an led light tabel identical :smile:

    yesterday made the 256 step wedge and guess what a new problem GRRRRR i took a fresh sheet of hahnenühle photorag and for an 12x12cm image i used 16 drops which was plenty

    BUT when the paper dried it has streaks and the coating was not even. could this be that the paper was to dry? or that i didnt mix the chemistry well enough?

    cheers janosch
     
  23. DennyS

    DennyS Member

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    I hope you didn't use the photo rag paper, it's for inkjet printing.
     
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    Janosch Simon

    Janosch Simon Member

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    no no my mystake i use hahnemühle platinum rag and as usual i changed 2 things to fix one and luckyli it worked :DDDDD first i was to sloppy to mix the the emulsion enough no brainer but before i swirled it 2-3 times now i swirl for 45sec to give it a good mix and result is a beautyfull smooth coat :D second thing i tested was useing an ultrasonic umidifier and boy my DMAX is back now i can start making prints ...one more thing need to finish calibration :DD
     
  25. ced

    ced Member

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    Hey Janosch what happened? You've disappeared on us, what is happening regarding the calibration?
     
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