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Thread: BTZS + Modern Incident Meter w/ Digital Readout

  1. #1

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    BTZS + Modern Incident Meter w/ Digital Readout

    Beyond The Zone System, 4th Edition, pp. 136, paragraph 2:

    "1. Take the bright light (high) reading.
    2. Take the shadow (low) reading.
    3. Subtract the low reading from the high reading (in stops).
    4. Add that difference to 5 (the standard minimum range) to find the total subject [brightness] range (SBR) in stops.
    5. Consult the EFS chart to find the appropriate film speed, and set it into your meter dial.
    6. With the meter pointer set on the shadow (low) reading, select the camera settings, and make the exposure. Record the SBR number.
    7. Consult the developing chart to find the development time that's appropriate for the SBR, and develop accordingly."

    Those instructions likely refer to meters whose display is a dial, not the more modern meters which give results in numbers.

    Would it be correct to re-state numbers 5 - 6 as follows ?

    5. Consult the EFS chart for your film/developer combination, find the appropriate film speed for the specified SBR, and set your light meter to that speed.
    6. Take the shadow (low) reading again, and expose with the settings recommended by the meter. Record the SBR number.

    This may all be obvious to BTZS afficionados, but as a newcomer, I am confused with the nomenclature - particularly because my current meter (Pentax Digital Spot) reads in LV, while my ancient Incident meter has a dial, and gives results in terms of EV.

    I'm also aware that the ExpoDev software automates much of this, and incorporates additional variables like flare, filter factor, bellows extension, reciprocity, etc - but I'm trying to grasp the core principal here.

    Thank you

  2. #2

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    Re: BTZS + Modern Incident Meter w/ Digital Readout

    I can change iso on my cheap digital meter without loosing the shadow reading. It just modifies the exposure recomendations. Sekonic L308S off ebay.

  3. #3

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    Re: BTZS + Modern Incident Meter w/ Digital Readout

    Ken buy yourself the Palm pilot and theExpoDev software. It is all very inexpensive. You can get a small tool from the ViewCamera store called a powerdial which is a calculator for both incident and spot readings.
    Failing that if you are on Skype someone who is actually a user of the system will be able to help. Heck "pester" Sandy he probably has as great or greater working knowledge of BTZS as anyone. Only those that use the system actually understand the system. On our forum here you will get 90% answers from people who have not any idea about BTZS and just in their naivety think it is the same as the ZS, which it is not.

    Steve

  4. #4

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    Re: BTZS + Modern Incident Meter w/ Digital Readout

    Thanks for the recommendations. I mentioned in my post that I am aware of the ExpoDev software, but I'm trying to grasp the fundamental concept. Meters with dials often behave differently than meters with numeric readouts, and explanations can be... ambiguous.

    I actually have a Power Dial, and find that the exposures it recommends are at odds with what Phil Davis recommends on pp. 136 paragraph 2 of the latest edition of his book. In Appendix 5, he gives some instructions about its use, but there are some questions about which ISO to set, which remain unanswered. I get the impression that he was rushed by one reason or another, when adding that section to the book. For example, he tells you to use the box speed of your film - except 250 when shooting TXT, and 80 when shooting FP4. He doesn't explain why those films would be handled that way - and not others. Many people shoot those films at lower-than-box speed of course, but it's surprisingly inconsistent, considering how earnest and meticulous the bulk of his writing are.

  5. #5

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    Re: BTZS + Modern Incident Meter w/ Digital Readout

    Ken (or anyone),

    I am not steeped in BTZS methodology, but I have a basic (and probably stupid) question regarding steps 1-4 in the opening post. I use a Pentax Digital Spotmeter and to find the SBR I just meter the brightest spot where I want detail and the darkest spot I want detail. The difference in stops is the SBR--or so I have assumed.

    Following the above steps I am imagine this: shadows = EV 8; highlights = EV 13. Difference = five stops. Add that to 5 and you get 10 for the SBR. Huh?

    Feel free to smack me upside the head and tell me to get Phil's book, but I am curious as to why it seems so complicated.

    Also, Ken, I thought the Pentax meter's LED viewfinder display was in EV numbers. Is that not the case?



    Jonathan

  6. #6

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    Re: BTZS + Modern Incident Meter w/ Digital Readout

    Ken with the systen I didn't really get a handle on it until I shot and processed a couple of negatives. I do admit to going virtually straight away to the ExpoDev because of the many calculations it does for you. I have the full kit - the WinPlotter program and the ExpoDev. I do all my own testing and also test film occassionally for friend here in Australia. Me personally, I cannot be bothered now to "understand" the system [I do] because it is absolutely flawless. I still suggest you have a one on one chat with someone like Sandy or one of the others in the US who is a full user. A half hour phone call would probably cost you about $1.

  7. #7

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    Re: BTZS + Modern Incident Meter w/ Digital Readout

    I am not an afficionado but it seems that the intent of 5&6 is simply to place the shadows. (Shooting to the shadows.)

    There appears to be an adjustment to the EI, which makes sense given the change in process, but then there is another offset thrown in for readings in shadow.

    The language used is confusing and the double offset (for EI then shadow) seems overly complicated too.
    You can't depend on your eyes when your imagination is out of focus. ~ Mark Twain

  8. #8

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    Re: BTZS + Modern Incident Meter w/ Digital Readout

    Quote Originally Posted by jcoldslabs View Post
    Ken (or anyone),

    I am not steeped in BTZS methodology, but I have a basic (and probably stupid) question regarding steps 1-4 in the opening post. I use a Pentax Digital Spotmeter and to find the SBR I just meter the brightest spot where I want detail and the darkest spot I want detail. The difference in stops is the SBR--or so I have assumed.

    Following the above steps I am imagine this: shadows = EV 8; highlights = EV 13. Difference = five stops. Add that to 5 and you get 10 for the SBR. Huh?

    Feel free to smack me upside the head and tell me to get Phil's book, but I am curious as to why it seems so complicated.

    Also, Ken, I thought the Pentax meter's LED viewfinder display was in EV numbers. Is that not the case?



    Jonathan
    Hi Jonathon,

    For a start BTZS is not the zone system as most apply it. I just plugged you figures into my Palm with ExpoDev and we first need to establish at what "zone" your brightest highlight falls. Phil suggested 3 and 7 so going by his recommendation your metering gives an SBR of 8.8 with an exposure of 1/2 sec @ f11 1/3 developed for 5:27 -- however if you are basing your range on 3 and 8 then the sbr is 7 with 1/2 second @ f 11 2/3 processed for 8:23. --- Figures based on my film test.

    Edit : Meant to add that the algorithim used for incident and spot metering seem to be different but give the same results for a scene metered correctly.

  9. #9

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    Re: BTZS + Modern Incident Meter w/ Digital Readout

    Steve,

    Thanks for the quick calculations on my behalf. I wasn't expecting a free tutorial in BTZS, but your reply helps my conceptual understanding.

    Jonathan


    EDIT: I've still got my old Palm III lying around. You mean it can still be used for something?

  10. #10

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    Re: BTZS + Modern Incident Meter w/ Digital Readout

    Quote Originally Posted by jcoldslabs View Post
    Ken (or anyone),

    I am not steeped in BTZS methodology, but I have a basic (and probably stupid) question regarding steps 1-4 in the opening post. I use a Pentax Digital Spotmeter and to find the SBR I just meter the brightest spot where I want detail and the darkest spot I want detail. The difference in stops is the SBR--or so I have assumed.

    Following the above steps I am imagine this: shadows = EV 8; highlights = EV 13. Difference = five stops. Add that to 5 and you get 10 for the SBR. Huh?

    Feel free to smack me upside the head and tell me to get Phil's book, but I am curious as to why it seems so complicated.

    Also, Ken, I thought the Pentax meter's LED viewfinder display was in EV numbers. Is that not the case?



    Jonathan
    Spot meter readings, high minus low, gives you a real measured SBR.

    Incident metering doesn't read SBR directly, because it doesn't read the reflective brightness value of specific points like the darkest shadow, it measures a much larger portion of the scene, so SBR has to be inferred by adding the 5-stop constant to the difference.
    You can't depend on your eyes when your imagination is out of focus. ~ Mark Twain

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