BTZS

Discussion in 'Alternative Processes' started by philsweeney, Jun 3, 2004.

  1. philsweeney

    philsweeney Member

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    Do alt printers, using BTZS tests, use 90% for IDmax for their ES (exposure scale) calulation? I was thinking: versus silver gelatin papers, I should try 95 or 100%.
     
  2. Jorge

    Jorge Inactive

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    I use 90%, exactly as Phil recommends. As Arentz writes, all you need are convincing blacks.
     
  3. sanking

    sanking Member

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    It depends. For carbon printing I use about 95%. For kallitype and Pt./PD. work, the lack of separation in the shadows could justify a figure of as low as 80-85%.

    Sandy
     
  4. philsweeney

    philsweeney Member

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    Sandy and Jorge: I need a little more help. All pyro negatives are measured in blue channel mode. Although I believe it could be done in visual mode also, resulting in a lower number of units. I believe the blue channel mode increases accuracy and if I had a UV mode even greater accuracy. I did do a PSP test with D76 and delta 100. I did the test twice to verify repeatability. For ES I have taken one of my test negatives (for example a WD2D test negative from the film tests not the stouffer test tablet) and contact printed to my paper. I'll call the test negative the "stained tablet." My premise is the stained tablet will give the correct ES for a WD2D negative to print to my selected paper, etc. To do this I used the WD2D stained tablet as the step tablet in plotter for the paper tests. Does this seem correct for dealing with the pyro negative for use in BTZS? Using IDmax% = 90% I have an ES of 1.27 from a WD2D negative obtained via the described tests for printing to strathmore 400 watercolor kallitype using 4 ml dichromate.

    Some cursory tests with AZO grade 2 and the same premises resulted (IDmax% = 90%): ES scale for stouffer tablet 1.36; WD2D negative, 1.19; pyrocat (1-1-100), 1.02. These results seem to indicate pyrocat gives more effective printing negative densities.

    Compared to D76 negatives my film tests with pyro negatives (pyrocat, and WD2D) result in speed curves that are "zig-zaggy" whereas the D76 speed chart curve is a smoother curve. The pyrocat 1-1-100 chart is particulary questionable. Is this one of the other problems associated with pyro negatives and BTZS?
     
  5. Jorge

    Jorge Inactive

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    Phil, let me start from your last paragraph. What you mention might be a possibility and one of the objections Phil Davis has, having said that, I have not seen this problem in my tests, and I have seen some curves done by Sandy where his curves are also smooth. You need to remember Pyrocat is a proportional staining developer so your developing technique, agitation etc, might have something to do with this problem.

    I never saw the point of using a "stained" step tablet. My thinking is that even if you read them with the blue channel the total density remains the same. I did an experiment to verify this, I read the stouffers step tablet with a blue channel, with a visible channel and with a UV channel and the values were off only by 0.03. I know Herbst likes to do it this way, me I dont see the point. What we are interested to see is total density, what does it matter if it comes from silver or a combination silver/stain.

    If you are using the win plotter, you can adjust the points somewhat to smooth the curve and give you more reasonable results, I had one instance where I saw that the middle SBR curve had greater speed than the low SBR...clearly this did not make sense, so I adjusted the toe of the curve, only a couple of points and voilĂ  .....

    Ok, sorry for the long windedness, to answer your questions, no, there is no way to extrapolate visible readings to blue readings or UV readings, many people have tried including Arentz and none have been able to come up with a reliable formula. If you plan to use Pyrocat, you really need UV readings for alt printing. Pyrocat can absorb as much as 1 and 1/2 stop more UV than a non staining developer and as much as a stop more than a pyro negative. If you are using the win plotter you can send me your files and I will be glad to take a look at them, also if you want to wait, you can mail me your step tablets, I can read them with the UV channel and make you a win plotter file.
    Your reflection densities of 1.27 seem about right for kallitype so you seem to be on the right path.
     
  6. philsweeney

    philsweeney Member

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    Jorge, sounds like I really need the UV readings! So if I have the UV readings I would then just use the ES obtained from printing the stouffer tablet to my selected paper? And what about AZO: should I use the 1.36 ES (from my previous post) and use my blue channel negative readings or can UV readings of those be helpful also (since AZO has some UV sensitivity)?
     
  7. Jorge

    Jorge Inactive

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    Yes, if you have UV readings you can use the ES obtained from stouffers, if you dont then using the "stained" step tablet is better as it simulates the UV response.

    On azo, your light source is not an UV source, so I dont see any advantage of using UV readings for them. Although azo is UV sensitive you are not projecting any UV rays with a 300 watt bulb, so who cares, just use your normal ES obtained from the stouffers and the paper.
     
  8. sanking

    sanking Member

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    Phil,

    You can use BTZS testing with great accuracy if you read your stained negatives with a UV densitometry. Blue reading will be off (low) by as much as log 0.50 in the highlights compared to UV reading.

    The brown stain of Pyrocat-HD negatives provides much more actinic filtration of UV light than the stain of WD2D or other pyrogallol based developers. I compared the effect of stain of different developers and you can see the results at http://unblinkingeye.com/Articles/PCat/PCat3/pcat3.html. Just look at the charts near the end of this page. This is the main reason why Pyrocat-HD is so superior to the other pyro staining developers as a dual purpose negative for people who want to print with the same negative on both regular silver papers and in Pt/Pd. This is not true for AZO, however, as the high density range (as measured for blue light) required for printing with AZO results in a negative with UV density range that is much too high for Pt/Pd, though it might work with kallitype or straight palladium.

    I have not experienced any zig-zaggy results in curve data with either Pyrocat-HD or any of the pyro staining developers. If you are getting any it may be a result of the light source producing more fall-off of UV light in certain parts of the circle of illumination than in others. I would suggest increasing the circle of illumination of the light on the baseboard to at a diameter of at least three times the width of the film being tested, and then using only the very center of this circle.

    Sandy
     
  9. roy

    roy Subscriber

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    Unless I am missing something here, does this mean that by not using a UV reading densitometer, the assessment of pyro developed negatives is going to be a bit of a "hit and miss" affair ? Or, conversely,can non-pyro developed negatives be assessed more accurately ?
     
  10. Jorge

    Jorge Inactive

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    If you plan on doing alt processes sensitive to UV only, then yes...if not, then the blue channel will work.
     
  11. sanking

    sanking Member

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    No, not exactly. You could simply print your pyro stained test negatives directly with your UV process and evaluate the results visually, which is the end result anyway.

    But if you expect to practice sensitometry with UV processes without a UV reading densitometer, then yes, the results, though not exactly a hit and miss proposition, will lack the accuracy we expect from BTZS testing.

    Sandy
     
  12. philsweeney

    philsweeney Member

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    Here is a copy of the email I just sent to Jorge:
    Hi Jorge,

    Thanks for the feedback. I have attached 2 plotter files. Just curious any observations you may have.

    I recognize some folks are not in agreement on the stained tablet thing! But I can tell you the developing charts from plotter (using stained tablets on paper for ES tests) are consistent with other testing I have employed. Whereas if I had used the ES obtained from the stouffer tablet versus the stained tablet, the charts would be way off compared to my visual experience. Also the speed chart for pyrocat, specifically, is way off. The speed chart for ABC seems OK, and the developing chart seems consistent with my other tests. I have just switched to WD2D over ABC and have little experience with it. Since I have used FP4 for so long with 3-4 developers I certainly can tell if I am selecting the correct speed. I am using the photowarehouse film now. My tests indicate it is FP4.

    Before getting a densitometer I used to borrow one and all my tests were with a zone board, and using HC110 and PMK I had good control. When testing pyrocat in this manner the 0.1 over fb+f tests for speed were misleading and not correct. I then made adjustments after visually assessing the negative. Using 0.1 over fb+f tests for speed, worked quite well for PMK, ABC and HC-110. So it appears I can use the developing charts, but I cannot use the speed data for pyrocat. I can use pyrocat with FP4 at 100 for AZO.

    I appreciate the offer to read some negatives and may ask you to do so in the future.

    On a different note I'd like to read your pmk/pyrocat article and its attendant plotter files.

    thanks

    phil sweeney

    I am seriously considering backing up and using D76 for a while. Everything is about tradeoffs to me and I'd like to have the control afforded by BTZS.
     
  13. sanking

    sanking Member

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    Phil,

    When printing with carbon, kallitype and palladium I have found that BTZS gives me very close control of the process. I assume this is due to the fact that these processes are sensitive to such a small band of the spectrum and our UV measuring densitometers are reading in the very middle of this band. So at least with your kallitype work BTZS should work fine, provided that use a densitoimeter capable of UV readings. Or it is possible that you might find a UV filter that cuts off light outside the UV band which you could use with your color densitometer. For exmaple, I use a Wratten 47b filter with my Gretage D200 in Visual Mode and the results are identical to a reading with the X-Rite 810 in blue mode.

    However, if your source of concern is that you can not get the precise control afforded by BTZS with silver gelatin papers, including AZO, with pyro stained negatives I must say that I don't have a solution. The fact of the matter is that the blue filter of a color densitoimeter does not exactly match the paper sensitivity of either regular silver papers or of AZO, plus there is the complication of the light being used to expose the print.



    Sandy
     
  14. philsweeney

    philsweeney Member

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    Jorge and Sandy: thanks for the help and feedback. At least I know what some of the limitations are and what are the successful experiences of others.