Has anyone worked with BTZS?

Discussion in 'Film Discussion and Q & A' started by Mitica100, Jul 8, 2006.

  1. Mitica100

    Mitica100 Moderator Staff Member Supporting Member

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    Also known as Beyond The Zone System, this method uses testing the film and the camera to determine the best exposure/development ratio.

    I am intrigued by it since LF photography means much more expensive film, hence not wasting film/money in the process of creating a good photo seems like a good idea.

    This works in any format but it's most practical in Large Format.

    Here is a link:

    http://www.btzs.org/

    Anyone used this method?
     
  2. Torus34

    Torus34 No longer a newbie, moving up!

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    The biggest drawback to BTZS or the Zone system: roll film users who do not want to devote an entire roll to a single exposure. It's taken me a bit of a while to develop [sorry!] my own way of dealing with 35mm/120 roll film exposure/development/printing in order to end up with an optimal print.

    This doesn't mean that I don't appreciate the nuances of such refined systems for sheet film photography. The proof of their efficacy is evident in every Adams print.
     
  3. Hertz van Rental

    Hertz van Rental TPF Noob!

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    BTZS is just the basic application of film sensitometry.
    Several of us spent 3 months doing investigation and work on this, or something similar, when I was at College in the late 70's.
    We came to a number of conclusions - the main one being that it was largely a waste of time.
    To begin with you have to standardise your processing and standardise your lightmeter. Then do a number of test rolls of a test target and use a transmission densitometer to determine the optimum exposure. This can take several days.
    You have to re-do this whenever you start a new batch of film (there are variations between batches).
    You also have to do it for every lens you own or will use and do it for every aperture (there are minor variations between apertures so f8 on one lens will not necessarily be exactly the same as f8 on another).
    You have to do it for every camera body/shutter you will use (again there are minor variations between shutter speeds).
    And of course you have to do it for every filter.
    You also have to do it for your printing system and photographic paper.
    You end up with a complex set of tables which gives you the minor variations (for a particular batch of film using a particular camera and lens at a particular aperture and shutter speed) so that you can make minor processing changes to compensate.
    We discovered that in most situations the minor variations cancelled each other out and when they didn't the variation was rarely more than 1/10th of a stop. For an 'average' scene this gives you an exposure variation overall of somewhat less than 1%.
    Whilst this can be picked up using a densitometer we found that visually it was on the threshold of noticeability - that is to say, you weren't sure if you could see a difference.
    To summarise, the outlay in time, materials and money far outweighed the gains in quality. The later were at best marginal anyway.
    It did give us a far better understanding of film and the discipline required gave us total control but the whole thing is too cumbersome for most practical photography.
    Like using a 500 tonne steel press to crack a walnut. In theory it will work...
     
  4. Torus34

    Torus34 No longer a newbie, moving up!

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    While I found the Zone system too restrictive, understanding it gave me the knowledge needed to consistently produce acceptable prints.
     
  5. Hertz van Rental

    Hertz van Rental TPF Noob!

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    Just to be pedantic, this is more or less what you are doing when you shoot off a roll of film.
    Shutter and aperture combinations may vary but each frame on one roll of film should receive the same amount of light as every other frame on that roll of film. If it gets less you are under-exposing, if more over-exposing. :hertz:
     
  6. Torus34

    Torus34 No longer a newbie, moving up!

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    Pedantry spoken here. You're correct, of course.

    What I was obliquely referring to was the manipulatuion of development time in order to compensate for other than 'normal' contrast ranges. Old saws such as 'Expose for the shadows and develop for the highlights.' serve as examples. Difficult to do if the shadows of one scene are three zones higher than those of another on the same roll.
     
  7. Mitica100

    Mitica100 Moderator Staff Member Supporting Member

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    It does sound like a good idea then, since I'm going to study the LF. Anyway... keep the coversation going, I'm learning! ;)
     
  8. Hertz van Rental

    Hertz van Rental TPF Noob!

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    To continue the pedantry, this is a somewhat different kettle of fish.
    The adjustment of the contrast range of a film (B&W here, colour poses problems that largely preclude such manipulation) is usually dictated by lighting conditions.
    The exposure that a particular film requires is dictated by it's ISO rating, or sensitivity.
    The adjustment of the contrast range is dictated by the Contrast Index (or Gamma) of the film.
    Although you can alter the Gamma by under/over exposing slightly and then compensating for it in development you do not change the sensitivity, and therefore the base exposure requirement, of the film.
    In practical terms this means that providing you shoot a roll of film off under the same lighting conditions then there isn't really a problem. Difficulties are only experienced if conditions change, which is what generally happens if you take several days or more to shoot off a film.
    But to put it bluntly if you are working at that level then you don't really need to worry about controlling contrast.
    To put contrast into perspective, a bright overcast day will give you a contrast range of about 7 stops, which is what standard exposure/processing times are aimed at.
    A foggy day will drop the CR to 5 stops or less.
    A clear sunny day on snow/sand will give you something like 9 stops.
    Including sky/sun or other bright lights will, of course, push the CR way beyond this.
     
  9. Torus34

    Torus34 No longer a newbie, moving up!

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    My dictionary lists pedantry [thumbs pages] as an ostentatious display of knowledge.

    What you are providing is not pedantry at all, but rather good, solid basic knowledge.

    For those following your comments, could you be so kind as to complete the information on contrast ranges by covering the CR of the average b&w film and the CR of the average b&w paper?
     
  10. Hertz van Rental

    Hertz van Rental TPF Noob!

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    My dictionary defines a pedant as someone who is excessively concerned with details especially in academic work. Pedantry is a display of such. ;)

    The average b&w film has a contrast range of something like 10 or 11 stops between Dmax and Dmin.
    The CR of the 'average' photo paper is approximately 7 stops between Dmax and Dmin. 'Average' being Grade 2*.
    It can be seen that whilst it is possible to record quite a wide contrast range on the film, the paper is unable to reproduce this.
    The reason paper has a lower CR is because it works on reflectance and not transmission, having a paper base rather than a clear one.
    The useful range of the neg is therefore limited to the range that the paper is capable of reproducing.
    In practical terms 7 stops is usually adequate for most subjects, but you do run into problems when the tonal range of the subject is beyond what is recordable.
    This is why you hear so many complaints about landscape photographs: 'why is the sky white and featureless?'
    There are several things that can be done to 'cheat' on the contrast range.
    Use of contrast filters (yellow, orange, red, green), contrast adjustment through exposure/development, dodging and burning, pre-flashing.
    Sometimes you need to use more than one method to get the desired result.


    *Ideally, for optimal tonal reproduction the characteristic curve of the paper should match that of the neg.
    This is why there are a number of different grades of photo paper allowing the selection of 'best fit'.
    Because photo paper is designed to always develop to Dmax (whereas film isn't) very little developmental manipulation can be done except around the mid tones.
     
  11. Torus34

    Torus34 No longer a newbie, moving up!

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    Pedantry or not, as you wish, your explanations were clear and, speaking for myself, much appreciated.

    Thank you.
     
  12. Mitica100

    Mitica100 Moderator Staff Member Supporting Member

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    Adding my own thanks as well.
     

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