BTZS Testing on negatives developed in Pyrocat-HD

Discussion in 'B&W: Film, Paper, Chemistry' started by Jim Moore, Aug 6, 2004.

  1. Jim Moore

    Jim Moore Member

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    My X-Rite 361T Densitometer arrived yesterday so I am ready to begin BTZS testing on my film developed in Pyrocat-HD. The first film I will be testing is TMAX-400.

    I know that I will need to read the Pyro negatives using the "UV" mode on the Densitometer, but since I don't have a "Pyro Stained" step wedge I'm not sure how to handel the reference reading from it. (Does that make any sense?)

    Do I measure my step wedge in "UV" mode also?

    Thanks!

    Jim
     
  2. Francesco

    Francesco Member

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    You expose your step wedge onto the TMY (5 or 6 sheets perhaps) and then use your densitometer on the TMY (about 5 or 6 sheets developed for different times) after it has been developed in Pyrocat HD. The step wedge is not measured and hence does not have to be stained. Good luck!
     
  3. Jim Moore

    Jim Moore Member

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    Thanks Francesco!

    I thought that I needed to measure my step wedge and enter the readings in the first column of WinPlotter and the program used that as a base to calculate the curve...

    Or am I making this more complicated that it is :tongue:
     
  4. Francesco

    Francesco Member

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    Not complicated at all. Contact print the Step Wedge onto 6 or so sheets of TMY. Develop each sheet at different times on PYROCAT HD. Once dry, measure each step in each sheet for density, using the proper channel to read PYROCAT negs. Input them onto the program. So, with 6 sheets you will have 6 columns of varying ranges. I have not used the program in over 8 years (mainly because I no longer need it) but I believe that this is all it needs to generate the various reports.
     
  5. Jim Moore

    Jim Moore Member

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    Thanks again Francesco.

    Attached is a screen capture of my Delta-100 film test. In my WinPlotter program when you create a new film the 1st column "Step Table" is there by default. It has "default" values in it and I assumed (I know I should never "assume" anything) that I needed to input the values from my step wedge there for the test results to be accurate.

    Jim
     

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  6. Francesco

    Francesco Member

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    Jim, leave it as default. And of course follow the right order of inputting the vales. You are using the appropriate channel to read Pyrocat HD negs in order to make them (or I like to say, convert them) into apples-to-apples comparison with the default numbers of the program. Using the UV mode essentially "converts" the numbers for use with the program (this is my take on it).
     
  7. sanking

    sanking Restricted Access

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    Actually this question is a little more complicated than it appears because there is a possibility that readings of a Stouffer step wedge will result in readings that are different in UV, Visual and Blue mode. If that is indeed the case I would recommend using the new values instead of the default values as appropriate, i.e. values read in UV mode if working with alternative processes, and Blue values if working with silver graded papers.

    However, the whole logic of this is not absolutely clear to me so I would be interested in hearing from other BTZS users on this.



    Sandy
     
  8. Jim Moore

    Jim Moore Member

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    Thanks Guys!

    I'm starting my testing now. I'll do up some curves using default, UV, and Visual and post them for your opinions.

    Thanks again!!

    Jim
     
  9. Helen B

    Helen B Member

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    Wouldn't you measure the step tablet in visual mode if you used it to expose TMY? Isn't the purpose of the 'Step Tablet' column to tell the program what relative exposure the film had?

    Helen
     
  10. Jim Moore

    Jim Moore Member

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    Helen,

    That is my question. Thanks for asking it so simply :D

    Jim
     
  11. sanking

    sanking Restricted Access

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    However, the relative log values of the step tablet densities, which are plotted on the X-axis, are being used to determine the the configuration, or slope, of the curve on the y-axis. If the two units are not calibrated by measurment with the same mode, or color of light, it would appear to me that the CI of the curve would be either artificially expanded or contracted (slope increased or decreased), assuming of course a difference in measurement with different modes.

    This situation does not exist when we work with traditional developers that yield neutral tones because the measurment system for both the original step tablet and the test strips is the same.

    And just for the record, there is often a difference between UV and Visual channel measurements of reference step tablets. For example, one of my Stouffer TP 45 step tablets measures as follows. In Visual mode, Step 1 = 0.05, Step 11 = 1.50, and Step 21 = 3.05. In UV mode the measument is, Step 1 = 0.10, Step 11 = 1.45, and Step 21 = 2.87.

    Sandy
     
    Last edited by a moderator: Aug 7, 2004
  12. Jim Moore

    Jim Moore Member

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    O.K. I only had time to develop three sheets tonight. I have three more that I exposed and will develop them tomorrow when I get home from work and add the curves.

    Details:

    TMAX400:
    Pyrocat-HD 1:1:100
    Super SideKick processor 75Deg 20RPM
    All negatives read using "UV" mode.
    Step Wedge readings taken in "Visual" and "UV" mode.
    WinPlotter "Default" table.

    1=UV
    2=Visual
    3=Default
     

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  13. sanking

    sanking Restricted Access

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    OK, I was very curious about this so I went back and compared results with an existing film tests, which was FP4+ in Pyrocat 1:1:100, using two different step tablet readings, both from the same step tablet but one made with Visual reading, the other with UV reading. The reading in Visual mode ranges from 0.05 at Step 1 to 3.05 at Step 21, and the UV reading ranges from 0.10 at Step 1 to 2.87 at Step 21.

    As I suspected there was a significant different in the curves as plotted depending on which of the step table readings was used. The differences affected effective film speed, CI, and SBR values. To be precise, here is the difference when both calcualtions are made base on 10 minutes of development.

    Step Tablet One, or the Default, made with Visual Reading: EFS=160, CI =.69, and SBR=8.3

    Step Tablet Two, or the one made with UV reading: EFS=100, CI=.76, and SBR=7.5.

    So my conclusion is that you do need to read the densities of the step tablet that will be used to expose your test negatives in the mode that will be used to measure these negaitves, and substitute these values in the WinPlotter program for the Default step tablet if the values are different.

    Sandy
     
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  15. Helen B

    Helen B Member

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    Sandy,

    How did you know which results were correct? I'm still having difficulty seeing why the step wedge density should not be measured in the mode that most closely represents the way in which the film is exposed - ie a measurement of the relative amounts of actinic light falling on the film.

    If the step wedge measurements are being used to calibrate the UV measurements (which is unlikely to be as accurate as the standard densitomer calibration procedure), how does the software know what relative exposures the film received?

    The question is: 'What is the purpose of the step wedge measurements - is it to tell the software what relative exposures the film had, or is it to calibrate the densitometer against the known UV transmission of a Stouffer step wedge?'

    Can the software be used with other step wedges?

    Best,
    Helen
     
  16. Donald Miller

    Donald Miller Member

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    Interesting dialogue on this subject. I also do not understand why one would measure the step wedge density in UV mode. The only time that this would appear to be a valid consideration would be when the step wedge exposure on film would be facilitated by UV light.

    The step wedge density would seem to be valid when measured by the densitometer channel most closely approximating the spectral qualities of the light that would be exposing the step wedge onto film.

    What am I missing here?
     
  17. sanking

    sanking Restricted Access

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    Helen,

    Forgive me if my explanations lack clarity but this is the first time I have considered this particular issue, and/or tried to explain it. My initial assumption would have been that the measurement of a neutral tone step wedge should be the same with both Visual and UV mode and in fact I don't fully understand why that is not the case.

    However, as to which results are correct I again offer the suggestion that the log density units of measurments on the X-axis and y-axis need to be the same, i.e, taken with the same measuring instrument or mode of measurement. Otherwise the distance between equal units of log measurement would have to be different on the x and y axis. So you have apple to orange log units. In the case of the example cited the step tablet measured in UV mode had a total DR of 2.77 (2.98 - .10) in contrast to the DR of the Visual mode reading of 3.0 (3.05 - 0.05). But the actual range of 2.77 is being expanded to a physcial range on the X-axis of log 3.0 units. As one could predict this expansion of the X axis will result in a shallower slope, i.e. lower CI, if the plotting is based on the Visual mode reading.

    With respect to your two questions.

    "What is the purpose of the step wedge measurements - is it to tell the software what relative exposures the film had, or is it to calibrate the densitometer against the known UV transmission of a Stouffer step wedge?"

    The purpose of the step wedge measurement is to establish a common unit of log density for the x and y axis.

    "Can the software be used with other step wedges?"

    Sure, but need to measure the step wedge with the same mode that you will measure the tests strips that are made from it.

    Best,

    Sandy
     
  18. sanking

    sanking Restricted Access

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    The color of the light being used to expose the film is irrelevant. The density could come from red, green, blue or UV light. The color might affect the contrast or density of the test strips but that would make no difference to the plotting.

    The key with the plot is that you must have the same measurment of density on the x and y-axis. If not, the curve will be artificially distorted because the units of measurements are of different length on the two axis.

    Sandy
     
  19. Donald Miller

    Donald Miller Member

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    Thanks Sandy...I understand now.
     
  20. gainer

    gainer Subscriber

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    The purpose of the H&D curve you get by exposing the step wedge on film is to see how the image will print on paper. The film should be exposed by the light you expect to use when exposing actual photographs. The step tablet as developed on film is what the paper will see and so should be read by blue light for graded paper. VC paper can be a problem as it is sensitive to blue through yellow but gives different contrasts with blue than with yellow. I have not found a really good way to measure the printable density range of stained negatives so as to get a good working print on VC without test strips.
     
  21. Helen B

    Helen B Member

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    "The film should be exposed by the light you expect to use when exposing actual photographs. The step tablet as developed on film is what the paper will see and so should be read by blue light for graded paper."

    Patrick,
    'Just out of interest' how do you think the step wedge densities (rather than the step wedge image on film) should be read? By the mode that most closely represents the light used to expose the film (eg visual), or by the light that will be used to measure the film negative densities (eg blue or UV)?

    Thanks,
    Helen
     
  22. gainer

    gainer Subscriber

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    If the step wedge densities were truly neutral it wouldn't make any difference. When you measure density, you measure the light incident on the wedge and the light transmitted by it and get the log of the ratio. When you use that same wedge to expose film or paper, the color of the exposing light will make a difference. The exposed and developed film may or may not be neutral gray. It certainly will not be neutral if it was developed in a staining developer. This copy of the step wedge will look different to paper than a neutral density copy would. If the purpose of reading the neg with a densitometer is to predict how a print of it will look, the densitometer should have the same spectral response as the paper. The spectral response of VC paper varies with the spectrum to which it is exposed.

    If that is the purpose, test strips are better that a densitometer for determining the printable density range of a pyro neg on any kind of paper.
     
  23. Helen B

    Helen B Member

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    "If the step wedge densities were truly neutral it wouldn't make any difference."

    If... the question of which mode to use would not arise. It appears from Sandy's measurements that some step wedges are not truly neutral. However, I agree with you that they should be neutral.

    Best,
    Helen
     
  24. sanking

    sanking Restricted Access

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    But they are not. I have quite a number of step wedges and every one of these has some kind of actinic filtration that results in a lower maximum density in UV mode than in Visual or Blue.

    Sandy
     
  25. Jorge

    Jorge Inactive

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    The acetate base exhibits some UV absorption, in my densitometer the readings are uniformly higher by about 0.09 units.

    IMO, one should use the readings that the film "sees", given that panchromatic film is more affected by visible spectra, I use the readings from the visible channel (blue light) when taking readings from the step tablet. I have not seen any difference in using either readings, since using the UV readings means the curve is shifted 1/3 of a stop to the right. If one is to take readings from stained negatives to "fit" to a given paper curve, then IMO one should read with the channel that the paper "sees" and fit the spectra so that the readings from the densitometer are equal to the spectra to which the paper is sensitive. For example, pt/pd actinic response is in the 290 nm range, my densitometer reads in the 390 range, this means my densitometer is less "sensitive" than the paper so I have adjusted the exposures of my negative to give 1/3 more exposure since my densitometer is reading 1/3 less density than what the paper "sees".

    It has worked for me. YMMV.
     
  26. Helen B

    Helen B Member

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    Jorge,

    I'm glad that at least one person agrees with me!

    I've also noticed that the base adds a uniform level of difference between the UV and visual readings (UV density being higher than visual, as Jorge's readings) - but this does not, of course, alter the relative exposure values. So in the case where the UV and visual relative densities (relative step to step) are the same, it should not matter whether UV or visual is used - the curve is just shifted along the x-axis. (I couldn't think of a concise enough way to describe this 'relatively neutral' aspect of base plus silver when I wrote my previous posts, so lazily used 'neutral'.)

    In that case (the UV and visual densities of the step wedge being uniformly different) it would not matter which mode was used unless the densitometer was out of calibration. Then it may be better to measure the step wedge in the mode in which you were going to measure the film density because then the calibration error would partially cancel - the curve would be stretched or compressed diagonally, but would maintain the same general shape. Note that the error would not be cancelled entirely.

    So, if your UV and visual density step wedge measurements are different by a non-constant value there is either something wrong with your densitometer or the density steps in your step wedge are not neutral. It is acceptable for the base not to be neutral, as long as it is uniform.

    The preferable way to avoid errors caused by the possible non-neutrality of the step wedge is to have a calibrated densitometer, and to measure the step wedge in the mode that most closely resembles the way the film will be exposed (usually visual) then to measure the image of the step wedge on film in the mode that most closely resembles the way in which the paper (or next stage in the process) will be exposed.

    How does that sound?

    Best,
    Helen