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Thread: Question On Subject Brightness Range

  1. #21
    Peter De Smidt's Avatar
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    Re: Question On Subject Brightness Range

    In the Zone System, Zone I is not a detailed shadow.
    "Why can't we all just get along?" President Dale, Mars Attacks

  2. #22
    Jac@stafford.net's Avatar
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    Re: Question On Subject Brightness Range

    In my modest experience those who obsess with the Zone System make no better pictures than those who use a reasonable compromise. The Zone System is for desktop photographers with too much time to post during their desk bound day-job.

    Keep in mind that Adams with huge input from Fred Archer (a pictoralist) developed the system when emulsions were not well standardized and often crap compared to today's products. Y'all would be lucky to find in Adams' notes the day he discovered color contrast filters.
    .

  3. #23

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    Re: Question On Subject Brightness Range

    Quote Originally Posted by Jac@stafford.net View Post
    In my modest experience those who obsess with the Zone System make no better pictures than those who use a reasonable compromise. The Zone System is for desktop photographers with too much time to post during their desk bound day-job.

    Keep in mind that Adams with huge input from Fred Archer (a pictoralist) developed the system when emulsions were not well standardized and often crap compared to today's products. Y'all would be lucky to find in Adams' notes the day he discovered color contrast filters.
    .
    Well... IMHO the Zone System is not good or bad, it's the photographer who is good or bad. A photographer should know what shadow detail will record the Z-II of his film+processing, this ends in knowing what kind of shadow detail will get recorded in those scene areas underexposed by 3 stops from ISO rating.

    What's about highlights, an skilled photographer should guess what density will reach in the negative, to adjust processing. With or without Zone System...

    Even films are well different than Super-XX, a film Ansel used, the present ISO rating also allows for 4 stops max underexposure before detail is lost, as the "n point" is at log H = 1.3 from toe.



    If we see the AA images... it would take a very good photographer to get similar good results with a modern film.

    To me present films are not better for the job, just less grain for same speed, but grain is not much a problem for 8x10, now and then.

    The great thing about LF is that we have similar tools than AA and Krash, and still it takes a sound photographer to imitate those masters, with not that great true advantage from tools.

  4. #24

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    Re: Question On Subject Brightness Range

    Quote Originally Posted by Pere Casals View Post
    the present ISO rating also allows for 4 stops max underexposure before detail is lost, as the "n point" is at log H = 1.3 from toe.
    Forgive me if I've misinterpreted the above sentence, but the ISO B&W Speed Diagram isn't about exposure range or underexposure. It is an illustration on how to determine b&w negative film speed. If you are interested in theory, standards are not the place to look unless the particular standard has an appendix. Safety Factors in Camera Exposure, C.N. Nelson, Photographic Science and Engineering, 1960 is the place to look. FYI, the contrast parameters are part of the Delta-X Criterion equation that ties a fixed density method into the fractional gradient method. Under the ISO contrast parameters, the fractional gradient speed point always falls Δ0.29 log-H to the left of Hm. Technically, this makes Hm an EI. It also proves Hm is not the minimum useful gradient point. Delta-X is explained in Simple Methods of Approximating the Fractional Gradient Speeds of Photographic Materials, C.N. Nelson and J.L. Simonds, JOSA, 1956.
    Last edited by Stephen Benskin; 11-Jun-2017 at 19:20.

  5. #25

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    Re: Question On Subject Brightness Range

    Quote Originally Posted by Stephen Benskin View Post
    Forgive me if I've misinterpreted the above sentence, but the ISO B&W Speed Diagram isn't about exposure range or underexposure. It is an illustration on how to determine b&w negative film speed. If you are interested in theory, standards are not the place to look unless the particular standard has an appendix. Safety Factors in Camera Exposure, C.N. Nelson, Photographic Science and Engineering, 1960 is the place to look. FYI, the contrast parameters are part of the Delta-X Criterion equation that ties a fixed density method into the fractional gradient method. Under the ISO contrast parameters, the fractional gradient speed point always falls Δ0.29 log-H to the left of Hm. Technically, this makes Hm an EI. It also proves Hm is not the minimum useful gradient point. Delta-X is explained in Simple Methods of Approximating the Fractional Gradient Speeds of Photographic Materials, C.N. Nelson and J.L. Simonds, JOSA, 1956.
    Hello Stephen,

    Thanks for that information, http://www.apug.org/forum/index.php?...ure-pdf.23850/

    Still I'm not sure how ASA/ISO major upgrade of 1961 relates to these (1959, 60) older documents, in 1961 box speeds were doubled, because the safety factor changed. So I'm not sure if the meter point is the same related to film speed.

    Click image for larger version. 

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    I think this is (to me) interesting to be discussed:


    I've a question, given this chart:




    the "n" point determines a precise amount of lux*second...

    Is this the same amount of light (irradiance) that a calibrated meter would recommend for a gray card ?

    (this will be aprox because meters vary at least 1/6 of EV because ISO 2720:1974 recommended K and C values)


    Regards,
    Pere
    Last edited by Pere Casals; 12-Jun-2017 at 03:51.

  6. #26

    Re: Question On Subject Brightness Range

    I think Doremus' answer in post 13 above is closest to my understanding. The only thing I would add to that is that exposure is primarily your choice, based on what you want to achieve (in other words, your visualisation of the final print).

    A literal interpretation of a scene, based on a standard progression of tones, might require an N, N-1, or N+1 exposure, but you don't have to follow the standard if you want to achieve a different effect. Photoshop makes it easier to achieve different interpretations of a given scene now, of course, but the choice you make at the time of exposure, in anticipation of how you will develop and print, remains of real importance, imho, and does to some extent differentiate LF film photography from other formats and digital.

  7. #27

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    Re: Question On Subject Brightness Range

    Quote Originally Posted by Pere Casals View Post
    Hello Stephen,

    Thanks for that information, http://www.apug.org/forum/index.php?...ure-pdf.23850/

    Still I'm not sure how ASA/ISO major upgrade of 1961 relates to these (1959, 60) older documents, in 1961 box speeds were doubled, because the safety factor changed. So I'm not sure if the meter point is the same related to film speed.

    Click image for larger version. 

Name:	_s.jpg 
Views:	15 
Size:	24.7 KB 
ID:	166009






    I've a question, given this chart:




    the "n" point determines a precise amount of lux*second...

    Is this the same amount of light (irradiance) that a calibrated meter would recommend for a gray card ?

    (this will be aprox because meters vary at least 1/6 of EV because ISO 2720:1974 recommended K and C values)

    Regards,
    Pere

    Hi Pere, I'm getting ready for work, so let me throw this out for now and I'll go into more detail later. n does not equal the meter calibration point. The contrast parameters are part of an equation. The standard doesn't discuss the equation because that is not the purpose of the standard. By adhere to the contrast parameter, the result will always be the same. Only when the processing is different, does the Delta-X equation need to be used. This means that the fixed density method produces an "accurate" film speed only under the ISO parameters. Here is the ISO speed diagram with Delta-X.

    Click image for larger version. 

Name:	ISO Speed Graph with Delta X equatioin.jpg 
Views:	15 
Size:	82.5 KB 
ID:	166010

  8. #28

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    Re: Question On Subject Brightness Range

    Quote Originally Posted by Stephen Benskin View Post
    Hi Pere, I'm getting ready for work, so let me throw this out for now and I'll go into more detail later. n does not equal the meter calibration point. The contrast parameters are part of an equation. The standard doesn't discuss the equation because that is not the purpose of the standard. By adhere to the contrast parameter, the result will always be the same. Only when the processing is different, does the Delta-X equation need to be used. This means that the fixed density method produces an "accurate" film speed only under the ISO parameters. Here is the ISO speed diagram with Delta-X.

    Click image for larger version. 

Name:	ISO Speed Graph with Delta X equatioin.jpg 
Views:	15 
Size:	82.5 KB 
ID:	166010
    Ok, I'll wait for your comments later...

    But let me point something... (talking for Normal development, for ISO calibration)


    The "n point" in the ISO rating is at 1.3 Log H from the toe.

    In this document http://www.apug.org/forum/index.php?...ure-pdf.23850/ the meter point is at 1.25 Log H from the toe, just 0.05 difference, this is 1.8-0.55 = 1.25

    So the meter point ("a" in the 1960 document) and the (ISO procedure) n point are the same irradiance (1/6 stop difference, perhaps)


    Click image for larger version. 

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    But I don't know if the meter point changed after 1961 new rules...


    My guess (not sure) it that yes, it changed, so under present specifications we should have 3 linearly underexposed stops plus toe, if toe takes one stop then we should have 4 underexposed stops, with some toe detail at -4. And -5 should be pure black. This is the same than with zone system gray levels...

    If I'm right (not sure) since 1961 the "n point" of ISO rating is at 0.3 Log H at the right of the C point of the 1960 graph. Simply the C point moved an stop (0.3H) to the left because 1961 rules doubled on box speed...

  9. #29

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    Re: Question On Subject Brightness Range

    Quote Originally Posted by Pere Casals View Post
    Hello Stephen,

    Thanks for that information, http://www.apug.org/forum/index.php?...ure-pdf.23850/

    Still I'm not sure how ASA/ISO major upgrade of 1961 relates to these (1959, 60) older documents, in 1961 box speeds were doubled, because the safety factor changed. So I'm not sure if the meter point is the same related to film speed.

    Click image for larger version. 

Name:	_s.jpg 
Views:	15 
Size:	24.7 KB 
ID:	166009



    I think this is (to me) interesting to be discussed:


    I've a question, given this chart:




    the "n" point determines a precise amount of lux*second...

    Is this the same amount of light (irradiance) that a calibrated meter would recommend for a gray card ?

    (this will be aprox because meters vary at least 1/6 of EV because ISO 2720:1974 recommended K and C values)


    Regards,
    Pere
    Look for a reflected light exposure meter to aim at 10 times the amount of light at m

  10. #30

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    Re: Question On Subject Brightness Range

    Quote Originally Posted by Bill Burk View Post
    Look for a reflected light exposure meter to aim at 10 times the amount of light at m
    Thanks, Bill

    So this is 3.3 stops of linear response for underexposure (Log210 = 3.3), before we are in the toe, as toe is defined by ISO speed method. The fourth underexposure stop it would be well in the toe, and -5 should be plain black. (With normal development...)

    So it looks that the charts made before 1961 had 1 stop more (safety factor) as rated speed was just the half. Before 1961 it was 20 times the amount of light at m, I guess... as the exposure meter had an ASA speed setting that was just the half...


    ...And the n point it was the irradiance targeted by exposure meters before 1961change, so today the n point is considered 1 stop overexposed.

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