BTZS exposure question for flat lighting

Discussion in 'Exposure Discussion' started by Paul, Aug 14, 2006.

  1. Paul

    Paul Member

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    Hi,

    I posted this message earlier at the BTZS.org forum, but since there is a lot more traffic here, I figured I would ask it here as well:

    This weekend I was photographing and old headstone in a nearby cemetery. The headstone was uniformly illuminated (I checked carefully) by bright northern light from a cloudless sky. The headstone was light granite. In zone system terms it would have been a 6 or so. I intentionally threw the background out of focus and as it was dark foliage for the most part, I ignored it when metering on the grounds that no matter what happened to it, it would always be darker than the headstone and thus make it stand out. What I did was take an incident reading from in front of the headstone and call it a flat 5 stop scene. I then metered using the appropriate ASA for such a scene. I have yet to develop it, but assumed at the time that I would give it the extra development a "flat" scene calls for. As I understand it, what I did was intentionally underexpose. When I develop I will extend development to compensate for this.

    My question as someone new to the BTZS is this: am I completely confused? Is this what I should have done, and if not, how should I handle such an exposure in the future? Could/Should I have metered the background and subtracted that EV from the headstone's, which might have given me a SBR of 7 or 8 and exposed accordingly? Or will what I do produce the same (or similar) end result.


    Thanks,
    Paul
     
  2. Donald Miller

    Donald Miller Member

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    From what you have related, I would say that after development you will have produced a negative consistant with your intentions.
     
  3. Paul

    Paul Member

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    Thanks.
     
  4. sanking

    sanking Member

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    Since you know the background will go very dark, and that is ok with you, it was fine to exclude it your metering. However, in metring I would have taken a shadow incident reading blocking off some of the light from the dome to simulate shadow values. This would have given you a slightly higher SBR, probably about 6, which would be more in keeping with my understanding of that kind of scene. If you develop for a SBR 5 you are likely to get more contrast in the headstone that you want. If you have BTZS exposure and develoment data for this film I would suggest developing for a SBR of 6, not 5.


    Sandy King
     
  5. Paul

    Paul Member

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    Thanks Sandy,

    I will give that a shot. I took two negatives of the scence with virtually identical exposure, so I can try one at the 5 SBR time and one at the 6 SBR time. The headstone had very little contrast and I think that it might be interesting to see if the extra development produces and image that has more impact than the actual object. In the future, I will try your suggestion of shading the meter a bit to increase the SBR.

    -Paul
     
  6. sanking

    sanking Member

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    Paul,

    Phil Davis writes about this kind of subject under Incident Metering of Unusual Subjects. What he notes is that the 5-stop range minimum assumes no modulation of illumination of any sort, and in fact every three-dimensional subject will exhibit some effect or light or shade.

    Sandy
     
  7. Paul

    Paul Member

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    Sandy,

    Just reread that section. Perhaps I was thinking too much in the field. I guess in the case of the headstone, shadows would be present in the carving, though not obvious to the eye.

    Thanks,
    Paul
     
  8. noseoil

    noseoil Member

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    Paul, not having an incident meter, I'm mum on this subject. One thing I will relate, which I think may be useful, is to keep track of this shot. Since it is a difficult lighting situation, you will have a good amount of information to track and try to remember for next time in a similar situation. Sandy's take on metering is sound, but it is still difficult to get a proper meter reading with this type of scene. Since you have two shots and the ability to track them differently, try to write down as much information as possible with respect to the exposure, sbr, development and finally the results you found in the prints. It helps to think a bit after you are finished, and writing it down will let you work better in the future.

    If possible, once you are done go back to the scene and do a few meter readings as suggested. Take the prints with you! This should help to clarify the light in your head and how to use it next time. One great feature of the BTZS numbers is the simplicity it allows in difficult lighting situations. Once you have a frame of reference, you will have a lot more leeway in development of these scenes. Just keep plugging away. Best, tim
     
  9. Donald Miller

    Donald Miller Member

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    There are any number of ways to present a photographed scene/object. I would still stay with a SBR 5 on a flatly lit head stone. The lower SBR will lead to enhanced local contrast. It is highly unlikely that you will exceed the local contrast limitations with a SBR 5 exposure/development on a single flatly lit element within the composition. Local contrast trumps overall contrast every time from where I sit.

    This is where, in my opinion, artistic interpertation departs from a realistic rendering.
     
  10. Paul

    Paul Member

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    Thanks for all the input.

    As I mentioned, I posted this same question at the BTZS.org forum and Phil Davis responded. I will not quote him here without permission, but to summarize his response he said that what I did was sound in practice and will probably produce a good if slightly dramatic print. He followed this by saying just what Sandy said: shadowing the meter with one hand would probably have given an SBR of 6 or so and yielded something a little more "normal". So Donald and Sandy (and I) are all right, so to speak. As I say, I may develop one for the SBR 5 time and the other negative for the SBR 6 time. I will post again with the final verdict.

    Thanks again,
    Paul
     
  11. Paul

    Paul Member

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    Hi,

    I developed both sheets of film (TMAX 400). I developed one for the time appropriate for a SBR 5 scene and the other for the time appropriate for a SBR 6 scene. Both were developed in D-76 1:1. I printed both negatives this weekend. The results: both produce acceptable prints, but the one developed as an SBR 5 scene is the better print. Details of the headstone that are crisp and apparent in this print are not nearly as well rendered in the print developed for as a SBR 6 scene.

    Now, before anyone bases their headstone metering techniques on this experience, be warned that this was not the most scientific of studies. For one thing, the sheet I developed as an SBR 6 scene was originally exposed for development as a SBR 5 scene. I reduced development when Sandy King suggested, logically, that I would probably end up with too much contrast. I suspect that if I given it the greater exposure a SBR 6 metering would have required, the differences in the negatives and resulting prints would have been minimized.

    Secondly, the prints are kallitypes, so a little extra contrast may be less damaging here than if I were printing on, say, silver enlarging paper. Furthermore, I was cheating a bit with my numbers. Operating on the assumption that a skilled printer's BTZS numbers are somewhat transferable, I took Dick Arentz's figures for D76 1:1 in his "Platinum and Palladium Printing" and increased them by 30%. (He recommends an increase of 20% over the platinum figures he lists in the appendix to get to the 1.6 he favors for palladium.) So, I assumed 30% above the platinum numbers would get me to the roughly 1.8 needed for kallitypes. I think I am close, but to tell the truth, a 40% increase seems like it might be warranted based on the results of some other negatives I developed. [Any thoughts on this issue would be welcome.] Given this, I may have unerdeveloped a bit and metering the headstone as a flat 5 stop scene might have been a bit much had I developed it as long as perhaps I should have. More testing is needed.

    -Paul