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  1. #1

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    BTZS and low contrast scenes

    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. #2

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    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. #3

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    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. #4

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    Quote Originally Posted by Kirk Keyes
    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

    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. #5

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    Quote Originally Posted by Kirk Keyes
    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

    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. #6

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    Quote Originally Posted by Kirk Keyes
    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.
    This is actually very common where I live.
    Technological society has succeeded in multiplying the opportunities for pleasure, but it has great difficulty in generating joy. Pope Paul VI

    So, I think the "greats" were true to their visions, once their visions no longer sucked. Ralph Barker 12/2004

  7. #7

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    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. #8

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    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. #9

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    Quote Originally Posted by mark
    This is actually very common where I live.
    Mark - where do you live?

  10. #10

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    Mark

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

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