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Thread: Why do some photographers use sensitometry?

  1. #1

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    Why do some photographers use sensitometry?

    In a recent thread Steve Simmons suggested that he was concerned because some people insist that densitometers are necessary to make great photographs. I personally have never heard anyone make that statement and donít really believe there is any great reason for concern on his or anyone elses' part. Most people who use sensitometry donít care at all how others approach their photography, and by the same token we donít need the KISS patrol to tell us how we should work.

    However, I thought it might be interesting to point out some of the reasons many photographers, especially large format workers, find that sensitomery helps us in our work, so I started to jot some idea down. Them I remembered that Phil Davis, creator of BTZS, had already set forth some good reasons in his book Beyond the Zone System, so I say to myself, why invent the wheel? Here are the reasons set forth by Davis to explain the advantages that sensitometry offers over the trial-and-error approach. Most of the language is directly from Beyond the Zone System, 3rd edition, pp. 3-6, but I have added a sentence or two, in parentheses.

    1. It is standard industry procedure so you will become familiar with the methods that manufacturers use to establish their published film speeds and paper contrast numbers.

    2. It is objective and efficient.

    3. The procedures provide much more data Ė and more accurate data, than can be discovered by trial-and-error testing. It also provides working information for all conditions of use, not just the specific conditions of the test.

    4. The use of sensitometry results in a dramatic saving in time and materials. (This is of tremendous importance if you print with very time consuming processes, such as carbon, or very expensive processes, such as Pt./Pd.)

    5. Sensitometry will add to your knowledge of the photographic process and suggest new way of controlling the image for your personal creative process.

    6. Contrary to common prejudice, sensitometry does not impose any technical restrains on your creative efforts. The notion that the more you know the less you can image is simply fallacious. If anything, itís more likely to be true that the less you know, the less you can imagine.

    7. And finally, knowledge of sensitometry provides you with the knowledge to distinguish between good and bad information. If Joe Fool Blow reports that such and such developer/film combination provides an increase in film speed of 500%, or some other such absurdity, you know how to test for yourself and determine if this is right or wrong. This kind of knowledge is liberating because it provides the tools to make your own determinations without having to pay homage to the gurus and their authority.

    In my own work I have found most of the above to be true. But if for any reason you donít care to embrace sensitometry, before you criticize it consider the fact that many of us who have worked both ways find many advantages in this approach, not the least of which is that it actually saves a lot of time. Bear in mind that we ďrocket science photographersĒ did not began our lives in photography with a densitomer stuck to our hip and logarithms rolling off our tongues. In fact, I only started working with sensitometry about 10-12 years ago, and have hundreds of nice negatives that were made long before I ever measured a negative density. In fact, many of them were made just by dutifully following the manufactures directions for speed and developing by the charts. But I spend a lot less time today testing film than in the days when I used the trial-and-error method, or even later when I worked with the Zone system.
    http://www.sandykingphotography.com/
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  2. #2
    おせわに なります! Andrew O'Neill's Avatar
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    Why do some photographers use sensitometry?

    A densitometre enabled me to learn about my film faster. I used it routinely to help me decide proper exposure and development of my unsharp masks. I really miss that little tool as it was stolen along with all my other stuff.

  3. #3
    Kirk Gittings's Avatar
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    Why do some photographers use sensitometry?

    Just an ignorant question. Why is BTZS quicker to use than the Zone System for determining things like personal asa.
    Thanks,
    Kirk

    at age 67
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  4. #4

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    Why do some photographers use sensitometry?

    Sandy has misrepresented what I said.

    Here was my post

    "I am concerend about the tendency to make large format seem like rocket science. The insistence by some that a densitometer is needed, all of the match that is put forth for focussing, etc. This approach will intimidate some people and may discourage their entry into using a big camera with sheets of film.

    It would make more sense to me to present this more 'scientific' approach as one way but also to allow for the possibility of a softer approach. It feels like a little too much dogma sometimes about the right(one and only way) to do things. I realize that some people are more comfortable with a little harder approach but others see numbers, formulae, and a densitometer, as roadblocks.

    Any comments?

    steve simmons"

    This started a very long and interesting thread that I would encourage people to read.

    steve simmons

  5. #5

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    Why do some photographers use sensitometry?

    As I have said before, and to which Sandy has not responded, is that it is not necessary to study the working of an internal combustion engine to drive a cxar and it is not necessary to study metalurgy to be a metal sculpture. Some will do both while others will just drive the car and others will make wonderful photographs.

    steve simmons

  6. #6

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    Why do some photographers use sensitometry?

    Kirk Gitting: "Just an ignorant question. Why is BTZS quicker to use than the Zone System for determining things like personal asa."

    Kirk,

    With BTZS you do only one set of negative tests. You expose five or six sheets of film to a 21 step transmission wedge using a light source of known value, or with a sensitometer which is even better, and you develop the five or six sheets of film in your chosen developer for different periods of time, ranging from 1/4 of what you believe to be normal development time to as much as two or three times normal time. Then you plot the curves from the five or six sheets. This takes about 1.5 hours and gives you all of the information you will ever need to expose and develop your film for a wedge range of differences processes and a wide range of lighting conditions. The test results will show you how long you need to develop for a given negative average gradient, or for any value of N expansion or contraction or subject brightness range.

    The results work for all processes, from silver which needs a relatively low average gradient, to processes such as palladium and albumin that require very high contrast negatives. And you get the effective exposure index for any given time of development, and this generally increases with time of development. I used plain Zone system before, and to get as much information would take you at at least 25X the time needed for BTZS, maybe as much as 50X.

    Assuming you continue to use the same film and developer, this one test, which as I say takes about 1.5 hours to complete, gives you all the information about exposure and development you will ever need. For any process. For any condition of subject lighting, from N-3 to N+3, assuming the film and developer permit that degree of expansion and contraction. And as I say, you will never need to test that combination again.

    Also, the data you get form BTZS testing can be used with either the SBR system, based on incident readings, or the Zone system.
    http://www.sandykingphotography.com/
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  7. #7

    Why do some photographers use sensitometry?

    Yep, and you did not respond to Brian's statement that some people read the owners manual.

    Kirk, the BTZS is much faster than the Zone system because it gives you far more complete information with fewer exposures. You expose your preferred method of printing to a step tablet, you measure the exposure index that the paper or process has and then you expose 5 sheets of film to a step tablet which will yield information about developing your film to the paper or process range from N-x to N+x.

    For example I like to use a middle range contrast solution for my pt/pd prints. So my solution #3 has a printing range of 1.45 density units. I then exposed 5 sheets of film to a step tablet, developed them at 5 different times, and obtained from this a range of N-5 to N+2.2 development and exposure (EI) times that will result in a negative with a density range of 1.45 units.

    Notice how powerful this is, if I change papers or process, I dont have to do the film tests anymore. I just plug in the new density range in the program and I now have different development/exposure values for the new process or paper.

  8. #8
    Clay
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    Why do some photographers use sensitometry?

    Kirk,

    The quick answer to your question as to why it is faster: the classical Adams-esque zone system does not explicitly recognize that film speed is inextricably tied to development. The BTZS system lets you expose 5 sheets of film, develop them at various times, and you have all the information you need to relate development to film speed, and subsequently, the ability to use this information to tailor your final negative density range to the exposure scale of the printing process you intend to use.

    That said, I understand the BTZS system, and I used it a lot for a while, but now it is just sort of stored in the grey matter. I mentally process this stuff on a intuitive level now, and it works just fine. A lot of photographers get to the same intuitive point by other routes, and it works just fine for them also.

    The criticism seems to be that some workers place an excessive amount of belief in the precision of this method, and that there are some people who try to carry out the exposure and development calculations to 4 signficant figures, all at the expense of creative visualization. I personally think this is somewhat of a straw man argument.

    Truly creative visualization is a rarity in any case, and is certainly not limited to the 'Palm Pilot' crowd, as a glance at any all-comers juried show will quickly confirm. At the very least, Phil Davis does not have a creative portfolio so well known that people continue to ape it ad nauseum, which cannot be said for the continued efforts by some to make a slightly better 'Clearing Winter Storm'.

  9. #9

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    Why do some photographers use sensitometry?

    Steve Simmons: Sandy has misrepresented what I said.

    Steve,

    IMHO I have not misrepresented in the least what you said. You may not have meant exactly what you said, or you may now want to nuance what you said, but you said what you said. And what you said was that you were concerned by "the insistence by some that a densitometer is needed."

    But my purpose in starting this thread is not to start another argument with you. I respect your work in promoting lage format photography, both in publishing View Camera and in the conferences. And I don't claim to be better or smarter than you, or to make better photographs.

    So please, let's just agree to disagree here and extend some respect to the other point of view. And we are responsible for our words, not for what we meant to say.
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  10. #10

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    Why do some photographers use sensitometry?

    Steve Simmons: "As I have said before, and to which Sandy has not responded, is that it is not necessary to study the working of an internal combustion engine to drive a cxar and it is not necessary to study metalurgy to be a metal sculpture. Some will do both while others will just drive the car and others will make wonderful photographs. "

    No, I have not responded to that and did not think that you expected me to? As a general statement I can agree with what you say, but I don't find the statement to be a particulary useful analogy to the discussin of the previous thread.
    http://www.sandykingphotography.com/
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