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  1. #1

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    Hi,

    one of my photography teachers told us a story that I thought was a bit of overkill as far as exposure goes. He said he was taking an interior of a church so it was a long exposure, over half an hour, so they worked out the L & D curve or such and worked out the exposure from that. Wouldn't it be quicker to look at the reciprocity of the film and go from there. Being a student I've been working with a few pro photographers and most just take a reading, shoot and bracket, with regard to v high or v low tones. Hell, some pros said after school no one cares about sensitometry ! He is a ditherey old guy but we just can't work out why go so far.......

    ta Ade

  2. #2
    Aggie's Avatar
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  3. #3

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    hmm..a small correction they are called H&D curves. But more importantly I wish someone would explain to me how they can calculate a 30 minute exposure from an H&D curve unless they made a family of curves specifically for long exposures.

    An H&D curve is used to represent tonal and exposure relationships at NORMAL times and from what I have studied and read it is impossible to correlate a timed exposure this long to a published H&D curve made with normal times. Perhaps he was talking about development of the film, given an exposure which records the minimal detail it is possible to "guesstimate" the development time.

    I could be wrong, but as you have explained it, I dont think it is possible to do this.

  4. #4
    Eric Rose's Avatar
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    I agree with Jorge on this one. It sounds like the old guy was spinning a good yarn to elevate his position as grand wizard in the eyes of his students. I've actually heard this story told by someone else once, but I politely only sneezed "bullshit" at the end of it.

    To find true reciprocity time one must do experiments such as Barnbaum did. That is why he gave us his tables to use rather than what Kodak published as their's are wrong.

    I recently did a 30 minute exposure of a dried up green pepper in a flower pot. Used Bruce's numbers and it came out perfect. Tried one using Kodak's numbers and it was grossly underexposed.

    Anyway that's my 2 cents worth. If this guy can actually do this get him to show you on paper how he did it and post his methodology here so we can all learn.

    Eric
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    "civility is not a sign of weakness" JFK

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  5. #5
    Aggie's Avatar
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  6. #6

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    I have Barbaum's book and I know the shot you are reffering to Aggie. But that is totally different.

    One of the reasons I like the BTZS better is that you start by defining the range your PAPER can accomodate and then you make a family of curves with film to adjust the developing to fit that range. So, for example if I have a situation where I have a 13 stop range I would lower the exposure index of the film from 400 to 200 and then develop for very little time. I am pretty sure this was Barbaum's situation, the woman is sitting against a pillar in full daylight and he is inside the cathedral looking out to her, so his brightness range is very high, but I doubt he went into reciprocity failure as the exposure would have been too long and the woman's movement would have been apparent. So he simply applied development controls for a high contrast situation.

    What Ta describes, if I understand correctly is that his teacher grabbed a published H&D curve and somehow was able to determine that he needed a 30 min exposure to take into account reciprocity failure from looking at this curve. IMO this guy is either a genious and he needs to write a book on sensitometry (which I doubt very much), or he is trying to show off and is actually giving out wrong information.

  7. #7

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    Oh and BTW, Barbaum pissed me off with this shot. I dont know why people come to mexico and the first thing they do is take pictures of poor people as if we were the only country that had them.

    On the same vein, a couple of years ago when I moved here, a french guy had an exhibition of photographs he had taken from the air all over the world, guess what he decided to shoot for mexico? the dump...yep, the &%· dump. Granted the dump for a 20 million people city is something to behold, but of all the beautiful things mexico has this moron goes and takes a shot of the dump. And waht is worse is that they showed and toured the exhibition. If it had been me I would have told the guy to chcange the pic or move on to another country, better yet go back to france....

    I know, I know is off topic but had to vent my spleen or I would have exploted.....

  8. #8
    Eric Rose's Avatar
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    Actually Bruce has taken and shows many beautiful photos highlighting the positives of Mexico as well.

    I agree with you however that once a country is pigeon-holed it's hard to break peoples preconceived ideas of what they will find once they go there. It's like when you first buy a car all of a sudden it seems you see so many more of them than you had noticed before.

    Oh another thing, Bruce went to all kinds of lengths to not have the woman in the pic acutally begging when he took it.
    www.ericrose.com
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  9. #9

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    Quote Originally Posted by EricR
    Oh another thing, Bruce went to all kinds of lengths to not have the woman in the pic acutally begging when he took it.
    LOL..yeah I am sure he did not want the picture blurred...somehow I doubt it was out of emotional sensibility. It is ok, as I said I have seen worse, and Barbaum does make beautiful prints.

  10. #10
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