BTZS and low contrast scenes

Discussion in 'Exposure Discussion' started by Kirk Keyes, Apr 12, 2005.

  1. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,267
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    Last year, I was in Death Valley, trying to take photos of patterns in the sand. I've got one of those newer Minolta Flashmeter VIs that can do both incident and reflected measurements. I used the spot meter while there and some of the scenes were only about 3-4 stops (reflected) between the darker and lighter portions of the scene. Using Acros and Xtol, I was able to develop the film enough to expand it out to where it prints well.

    Today, I was flipping through my copy of the BTZS book (3rd Ed.), and I thought back to the Death Valley stuff. So I was looking for a description of how to meter scenes of low contrast using BZTS. Using an incident meter, it looks to me that the BZTS system can't measure scenes that have SBR's less than 5. It also seems that it can't differentiate between a 5 SBR scene and a 3 or 4 SBR scene.

    I know you can determine development times for SBR ranges this low, but how do you actually measure them with and incident meter. Does photographer's discretion (i.e. override meter readings) kick in here?

    Kirk
     
  2. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,267
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    PS - I realize this is not a very common situation, but I can think of several other situations that this could occur, things like rock patterns or rock art.
     
  3. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,267
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    PPS - and I'm interested in determining the range to calculate the required development time for contrast expansion. If I was going to try to reproduce the original scene as it was, then a simple incident reading would do.
     
  4. Jorge

    Jorge Inactive

    Messages:
    4,532
    Joined:
    Sep 6, 2002
    Shooter:
    Large Format

    A couple of things, first a difference in reflected measurements of 3 or 4 stops is very different from measurements of Illuminance. If you have a shadow, however light and a bright "side" you can use the incident system as explained by Davis. OTOH like any metering system it does requires some experience and the situation you describe is a perfect example. There are times when an SBR of 5 just simply wont do, you have to use an SBR of 4 or even 3 and this can only be determined by experience.

    All the exposures in the BTZS are based on the shadow measurement, so in the case of a SBR of 3 or 4 you would still use the meter setting given to you by the shadow reading. Supposedly you would have already made your film tests and know how you should adjust the EI for extreme expansion.
     
  5. Ornello

    Ornello Inactive

    Messages:
    295
    Joined:
    Apr 3, 2005
    Shooter:
    35mm RF

    If there were only 3-4 stops between the brightest and darkest parts of the scene, that's the way it should be presented. Develop the film normally.
     
  6. mark

    mark Member

    Messages:
    5,270
    Joined:
    Nov 13, 2003
    This is actually very common where I live.
     
  7. Donald Miller

    Donald Miller Member

    Messages:
    6,242
    Joined:
    Dec 21, 2002
    Shooter:
    Large Format
    As Jorge mentioned it takes experience to know your process and your materials...

    Let's face it a SBR 5 is roughly equivalent to an N plus two development...there are some films and developer combinations that simply won't go there. A case in point is Bergger BFP 200 in any developer. Another is TriX in most off shelf developers. Beyond a certain development the overall density increases to the detriment of density range or contrast.

    So for extreme expansion a limited number of film and developer combinations exist.

    I don't think that this is a matter of a weakness of the BTZS itself...

    For really extreme expansion such as rock patterns etc, I would be inclined to try a lith film such as Aristo APH. I would work with dilute Dektol. From my experience in masking techniques, I know this particular film will build a density range beyond any continuous tone film that I have encountered. A benefit of this material is that there are no considerations of increased grain as there is in continuous tone materials. The cost of the film is extremely friendly too.
     
  8. Jorge

    Jorge Inactive

    Messages:
    4,532
    Joined:
    Sep 6, 2002
    Shooter:
    Large Format
    Mike Pry sent to me the curves for aerial pan x, his test with D76 show he can expand from SBR 4. Seems it would be a good choice for these kind of situations...
     
  9. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,267
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    Mark - where do you live?
     
  10. Peter Schrager

    Peter Schrager Subscriber

    Messages:
    2,119
    Joined:
    Jul 19, 2004
    Location:
    fairfield co
    Shooter:
    Large Format
    Mark

    Kirk-Mark lives in Colrado or Arizona-close enough
    Regards, Peter
     
  11. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,267
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    Jay, you're right. I was asking about how to meter in those situations.

    And if anyone is interested, I've gotten Xtol 1+1 at 20C with Fuji Acros to process to an SBR of 2.8 with a bit of base+fog, and to SBR of 3.0 with B+F of only 0.10 - so processing the film to those levels is definitely not a problem for me! Someday I'll try Xtol undiluted and save some time!

    So I guess the bottom line is I would just have to guess with the incident meter/BZTS metering, or use the spot meter as I did.
     
  12. Stephen Benskin

    Stephen Benskin Member

    Messages:
    1,646
    Joined:
    Jan 7, 2005
    Location:
    Los Angeles
    Shooter:
    4x5 Format
    Kirk,

    I don't want to take this thread off in a different direction, but the idea of how to address short luminance ranges would make for an excellent new thread. After all, there's more choices on how to deal with different luminance ranges than just processing and each choice has a distintive aestetic influence.
     
  13. sanking

    sanking Member

    Messages:
    4,813
    Joined:
    Mar 26, 2003
    Location:
    Greenville,
    Shooter:
    Large Format

    The important thing to understand about the scene you describe is that neither a reflected reading nor an incident reading will give you the correct exposure to reproduce the tonal values as you want them without interpretation. In other words, whether you use the Zone system or BTZS you have to make interpretative decisions as to how you want to the tones in the scene to reproduce on your print. You understand this with the Zone system and know how to accomplish what you want so no point to comment further about this.

    But what about BTZS. If you use an incident meter the reading will suggest an SBR of 5, and the reading will be the same regardless of where you point the meter. Such a reading if developed for an SBR of 5, will give you an overexposed and underdeveloped print. You will have a lot of detail in the shadows, with good separation, but muddy blacks. You can do one of two things to approximate an SBR that will suggest better exposure and development. One option is to go to one of the shadow areas of the scene and take a meter reading at that spot, note how much this EV values differs from the EV value of the first reading, and subtract from the SBR of 5 to give you a new SBR value, which could be 3 or 4. If there is not a real shadow area large enough to use for the reading you can simulate the shadows by shading the cone of the meter, take a reading, and then do the same calculation as above. Base exposure on an average of the shadow (or shaded) reading and the reading taken in full light. Or you could just double the EFS of the film and make the exposure based on the shadow reading.

    Development is another issue. Most developer/film combinations will easily allow for development of SBR values of 5 or less with regular silver gelatin printing, where the desired CI is about 0.60 and the exposure scale of the process is about 1.10. However, with AZO #2 and alternative processes, where the desired CI for the negative is 0.75 or even higher, and the exposure scale of the process is 1.5 or higher, the practical reality is that very few films are capable of development for a SBR of less than 5. So in a scene such as the one described by Kirk, unless you happen to be using one of the films that will allow a CI of up to 1.15 or 1.20 you are just as well off to expose and develop for the SBR of 5 and make adjustment with the process for more contrast. And the problem is not the developer, but the fact that most films have a maximum CI so that no matter how long you develop, or high much energy your developer has, the film reaches a point beyond which further contrast is not possible.



    Sandy
     
    Last edited by a moderator: Apr 13, 2005
  14. Sponsored Ad
  15. mark

    mark Member

    Messages:
    5,270
    Joined:
    Nov 13, 2003
    I live in North eastern AZ. The only thing I have found to combat the very low SBR is early morning, or late afternnot light. Shooting rock art is a PIA and have yet to get one that looks good.
     
  16. Donald Miller

    Donald Miller Member

    Messages:
    6,242
    Joined:
    Dec 21, 2002
    Shooter:
    Large Format

    Possibly we are not using the same terminology...I can go understand that might be the case...but how in the world did you determine your SBR numbers of 2.8 and 3.0?

    Your terminology indicates that you are processing to the stated SBR...that is erroneous if that is what you are intending to say. SBR is a measurement of the lighting contrast in the scene when the exposure is made...not something to be processed "to".

    The correct termininology consistant with BTZS procedure would be developing to a desired CI based on the SBR of the exposure.
     
    Last edited by a moderator: Apr 13, 2005
  17. Donald Miller

    Donald Miller Member

    Messages:
    6,242
    Joined:
    Dec 21, 2002
    Shooter:
    Large Format
    What do you mean that you can get an SBR of 3.3 with HP5+ and your developer? I remember you saying that you had read the BTZS book. Where does it express developing film to a given SBR?...SBR is a measurement of scene contrast and the correct terminology is to develop for the SBR inherent in the exposure. Never have I heard of anyone who is knowledgeable in BTZS express a SBR in tenths...

    Do you have a densitometer to measure these results that you are claiming? I would be interested in seeing the curves that you have plotted for this degree of expansion.
     
  18. sanking

    sanking Member

    Messages:
    4,813
    Joined:
    Mar 26, 2003
    Location:
    Greenville,
    Shooter:
    Large Format
    Donald,

    Although Davis does not give any examples in Beyond the Zone System, at least so far as I can recall, of SBRs below 5, some of his examples of metering for unusual lighting conditions appear to recognize that they are possible with incident metering. I have discussed the issue with a number of fairly knowledgeable persons who use BTZS, including Dick Arentz who uses both Zone System and BTZS, and many of us believe that BTZS does in theory allow for SBR values below 5, as in the situation Kirk described. And in fact, Davis' own plotter program does graph SBR values below 5.

    Sandy
     
  19. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,267
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    I've made a spread sheet that performs the calculations as layed out in the book.

    Thanks for the correction on the terminology. And your sentence above is exactly the kind of terminology I was trying to convey in the "CI of blank film" thread recently. You CAN develop film to a given SBR, just as you can develop film to a given CI. Even if the film didn't recieve a full range of exposure, like in the case of low contrast scenes - say 3 or 4 SBR, or even scenes with no contrast, such as a blank sheet of film.
     
  20. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,267
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    Most cetainly! There is no believe required. It's just a matter of making development tests out to times that allow the film to expand out to cover such low contrast ranges. (THat is, if possible - it is not with all film and paper combinations. I'm using regular silver paper and those are what I am discussing here).

    I may be mistaken, and feel free to correct me, but when I was flipping through my 3rd ed. BTZS book, I saw several graphs that have values down to 3 SBR. And look at the graphs at the bottom of this BTZS web site page:
    http://www.btzs.org/Articles/PSP.htm

    If I remember how to read these, the 16 min development for this film yields a film would match a SBR of 3.4. The G-bar at this point is 0.98. The instances I gave for the Acros above both had gradients greater than 1.00, and hence SBRs of around 3.

    It's just a matter of making an accurate meter reading for these situations. The film testing part is simple.
     
  21. Donald Miller

    Donald Miller Member

    Messages:
    6,242
    Joined:
    Dec 21, 2002
    Shooter:
    Large Format
    Sandy,

    I have no doubt that this is true. I have made a number of photographs where the SBR was below 5. My concern with the posts that preceded were that the terminology in two cases indicated development "to" a certain SBR...Those statements indicated something apart from my understanding of BTZS. My understanding is that SBR is a measurement of the inherent contrast in a given exposure. That this inherent contrast (SBR) is the determining factor for the degree of development the negative receives to achieve the CI that the printing material/process requires.

    I have difficulty believing that anyone metering a scene will arrive at a 2.8 SBR or a 3.4 SBR or any other numerical value expressed in whole and decimals. The terminology is still indicative of a misunderstanding on someone's part. I don't know who it is that is misunderstanding.

    In addition, Kirk Keyes posted the following after your post and I quote:

    I've made a spread sheet that performs the calculations as layed out in the book.

    Thanks for the correction on the terminology. And your sentence above is exactly the kind of terminology I was trying to convey in the "CI of blank film" thread recently. You CAN develop film to a given SBR, just as you can develop film to a given CI. Even if the film didn't recieve a full range of exposure, like in the case of low contrast scenes - say 3 or 4 SBR, or even scenes with no contrast, such as a blank sheet of film.


    I would like your thoughts on the information as it is presented here. Either I am missing something by a mile or this makes absolutely no sense.

    I look forward to your response to this.

    Donald Miller
     
  22. sanking

    sanking Member

    Messages:
    4,813
    Joined:
    Mar 26, 2003
    Location:
    Greenville,
    Shooter:
    Large Format
    This is a false analogy in my opinion. SBR refers to subject lighting conditions and is not in any way dependent on either exposure or development. CI is a slope created by minimum and maximum densities that is measured after development and results from both exposure and development. It might be ok to say that one can develop to an anticipated CI, but to say that one can "develop film to a given CI" when the final result is not the CI to which one is developing is not reasonable. One can develop for a given SBR and may or may not get the desired CI, but the SBR has its own reality, i.e. it existed apart from and outside of the reality of the desired contrast. CI has no reality beyond its realization. If you develop to a CI and get some other slope than what was intended then what you have is another CI.

    Sandy
     
    Last edited by a moderator: Apr 13, 2005
  23. sanking

    sanking Member

    Messages:
    4,813
    Joined:
    Mar 26, 2003
    Location:
    Greenville,
    Shooter:
    Large Format
    Kirk,

    Or let me put it another way. OK, so you decide to "develop your film to a given CI", but after development you discover that the CI is different from the one to which you "developed your film."

    OK, to what CI did you really develop your film? And is that question different than asking, "to what CI was your film developed"?

    In my opinion the matter is really very simple. The statement "develop the film to a given CI, " which apparently exists in the literature, is improper and confusing use of the language. Or most charitably, an abbreviation assuming the reader would understand that what was really meant was that one should "develop for a time that would produce a given CI."

    Sandy
     
  24. dancqu

    dancqu Member

    Messages:
    3,676
    Joined:
    Sep 7, 2002
    Location:
    Willamette V
    Shooter:
    Medium Format
    So a CI is the result. This + that x something else = result.
    Could you fill in just what the this, that , and something else
    might be? Likely, a constant or two, k values, are involved.
    Don't forget the givens. Dan
     
  25. Donald Miller

    Donald Miller Member

    Messages:
    6,242
    Joined:
    Dec 21, 2002
    Shooter:
    Large Format

    SBR is the contrast inherent within the scene. Development (developer, time, temperature and agitation) determines the CI one strives for consistant with the printing materials or process.

    CI is the result of the inherent scene contrast, exposure, and development of the negative.

    It is absolutely impossible to achieve a CI above zero if you have no exposure as in your example of a blank sheet of film.
     
  26. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,267
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    Here's my data for the Acros if anyone with the Winplotter software would care to crunch it for me.

    Fuji Acros, Xtol 1+1, 30 minutes, 20C. I get an SBR of 2.95, and a gradient of 1.19.

    Step Tablet density, film density measured with blue channel
    0.05, 3.59
    0.19, 3.35
    0.32, 3.17
    0.46, 2.98
    0.60, 2.84
    0.75, 2.67
    0.89, 2.49
    1.02, 2.31
    1.18, 2.11
    1.33, 1.93
    1.46, 1.79
    1.58, 1.63
    1.73, 1.44
    1.88, 1.24
    2.02, 1.04
    2.16, 0.84
    2.30, 0.60
    2.43, 0.45
    2.59, 0.30
    2.73, 0.20
    2.87, 0.16
    b+f, 0.09