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Thread: BTZS Metering Question

  1. #1

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    BTZS Metering Question

    I am reading the BTZS fourth edition book and have a question.

    Phil states that after the exposure has been made, you consult the chart to arrive at the development time depending on the calculated SBR.

    Am I right in thinking that you use these times instead of any previous times you may have used

  2. #2

    Re: BTZS Metering Question

    You're supposed to meter, which gives you zone 5 at the starting point speed. Close 4 stops to get your theoretical zone I. Ideally you want zone I to be at 0.1 above base+fog. But depending on the characteristics of your film (like if it has a long toe) you may want zone I to fall where the (somewhat) straight part of your film's curve begins.

    Ultimately, however, the paper is calibrated first & the film exposure & development tailored to get what you want on the paper. In theory. But you could have an ideal speed to get the most out of highlight detail & an ideal speed when you want to bring out better shadow detail also. There's no absolute.

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  3. #3

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    Re: BTZS Metering Question

    If you do the tests where you develop several sheets of film, (for example developing one sheet for 2 1/2 minutes, others for 4, 6, 9, 15 minutes)... And then if you created a chart of your own after reading the test negatives with a densitometer and plugging the numbers into the chart... Then yes. The chart would tell you how many minutes to develop your film for any particular SBR and you would use that time from the chart instead of any customary time you are used to.

  4. #4

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    Re: BTZS Metering Question

    Quote Originally Posted by Bill Burk View Post
    If you do the tests where you develop several sheets of film, (for example developing one sheet for 2 1/2 minutes, others for 4, 6, 9, 15 minutes)... And then if you created a chart of your own after reading the test negatives with a densitometer and plugging the numbers into the chart... Then yes. The chart would tell you how many minutes to develop your film for any particular SBR and you would use that time from the chart instead of any customary time you are used to.
    Thanks Bill. I need to go back a few chapters and re read this again until it starts to sink in, O the joys of been over 50

  5. #5

    Re: BTZS Metering Question

    I'm sorry, I was answering the metering question. It's actually a development question. 😄

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  6. #6

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    Re: BTZS Metering Question

    Quote Originally Posted by IanBarber View Post
    I am reading the BTZS fourth edition book and have a question.

    Phil states that after the exposure has been made, you consult the chart to arrive at the development time depending on the calculated SBR.

    Am I right in thinking that you use these times instead of any previous times you may have used

    Well BTZS, IMHO, has two different sections. First half of the book explains the physics, second part explains a couple of practical recipes.

    To me the important thing is to understand very, very well first half, it explains all.

    Look, you have a family of curves, for different development times, from that you can take the reading of any spot of the scene and you will know what precise density will deliver in the negative.

    I'd suggest that you do what I did to get practice. Just take a very contrasty scene, then use a spot photometer (SLR/DSLR) and the graphs of the family of curves. Then you can design how it will be your negative.

    You will be able to place your shadows at a desired density, also your higlights. You will be able to determine what will be lost... what will be more or less printable in the darkroom... (if scan + PS its easier... )


    You should be able to determine/predict what density will have every spot of the scene on the negative, then you can say that you understood very well the first part of BTZS. So you will need to correlate lux*second to photometer reading. (Saturated colors and filters add more complexity...)


    Tools you need is an Stouffer density wedge, a cheap handheld luxometer ($25) and a way to measure densities. Scanner can be used as a densitometer, just disable any scanner image treatment (gamma, curves, adaptative contrast...) and scan the Stouffer wedge at the side of your negative to compare, linearly.


    In this way you will know what will result from choices you make about exposure/development, next step will be using all that without thinking too much, with some practice in few seconds you will select N-1 or N+1, and the exposure.

  7. #7

    Re: BTZS Metering Question

    Pere, good point. I think the first half is fabulous in terms of presentation & I still get new ideas from re-reading it.

    I get the feeling Ian has made an exposure (actual photograph as opposed to a gray card or Stouffer wedge test exposure) and needs a development time from someone else's (published?) chart versus one he himself has come up with by standardizing his materials.

    To me, development is like wearing a tailored suit. Too many variables that a suit made for someone else just never seems to fit right.

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  8. #8

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    Re: BTZS Metering Question

    Quote Originally Posted by IanBarber View Post
    I am reading the BTZS fourth edition book and have a question.

    Phil states that after the exposure has been made, you consult the chart to arrive at the development time depending on the calculated SBR.

    Am I right in thinking that you use these times instead of any previous times you may have used
    Below is a graph generated for me by Fred Newman of the View Camera store, using the BTZS Plotter software. It shows recommended development times for different treatments according to the Zone System. (N is the development we would give for subjects of normal contrast range.)

    The graph is specifically for Ilford HP5+, tray-developed by me in my darkroom in D-23 1:1 at 70 deg F.



    You can see that the recommended time for N development is around 9 minutes and 20 seconds. For N-1, it's just over 7 minutes... etc.

    This graph was made by Fred exposing sheets of film under an enlarger with a step-wedge, then me doing the development, then Fred measuring the results with a densitometer. Thus, it is independent of any camera, shutter or lens. Because I developed the film, it was custom tailored to my method of agitation, my water, my thermometer, etc.

    I shared the Zone System graph here since you know that system, but the Plotter software delivers many graphs, such as how effective film speed changes with changes in development time, contrast, SBR, etc.

    BTZS generates a lot of charts with great precision, but the results are not essentially different from what we get by following widely published time/temperature charts. If the differences were substantial, we'd have to wonder why.

  9. #9

    Re: BTZS Metering Question

    Hi Ken, do you use D-23 often? I have been wanting to try that out.

    I don't doubt the accuracy of published charts, but where I do my tailoring is in modifying exposure, temperature, agitation, dilution, and development time to customize the look I get from a film.

    To me, it's not about just making a good negative by the book. It's about using recipes that bring out shadow detail, high/low contrast, emphasize apparent sharpness or to bring out texture in highlights. I look at the film as a canvas and to just develop by the book can be quite limiting. I don't begrudge someone for being satisfied just reproducing what's there, but we have to be true to our inner artist also.

    D-23 has been on my list of developers to try for a long time. It can be very striking.

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  10. #10

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    Re: BTZS Metering Question

    We need to know what normal is before we can depart from it

    I've been using D-23 for a number of years. See http://www.kennethleegallery.com/html/tech/D-23.php

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