L & D curve to work out exposure ???

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ader

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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
 

Jorge

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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.
 

Eric Rose

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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
 

Jorge

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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.
 

Jorge

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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.....:D
 

Eric Rose

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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.
 

Jorge

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EricR said:
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.
 

Jorge

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Aggie said:
Ok, I will let you be the judge of some of the few portraits i have done. They were taken in South america. I wanted to show more of the person, not and their diginity not their humble or undignified circumstances. I have to scan and such so bear with me that they are not immediately forth coming.

Ah, dont misunderstand me Aggie, it is the context within the pics that sometimes piss me off. For example if you find an old lady with an interesting face, deep brown skin wearing a typical hat, it is hard to resist, I have done it myself. But the Barbaum pic actually shows the woman sitting on the floor obviously in the act or getting ready to beg. This is the kind of thing that bug me. I dont mind a portrait made of a farmer or a poor person were the picture shows character and the face is interesting , but the kind of pictures showing people begging, or naked kids asking for money or in the middle of a dirty street in a ghetto really piss me off. Hell if I go to the US chances are under many of the bridges or underpasses in any city I can find a guy begging with a sign that says "help a vietnam vet" etc...how come the same guys who come here to take pics of poor people dont take those pics? That is what I am talking about, the deliberate exploitation under the guise of "art" when the problem is not just one that exists in this country.
 

Jorge

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Well, to get back on topic, you are correct Ta, for long exposures the best is to make personal tests, but barring that consulting the reciprocity tables would be the next best thing. The H&D curves thing your teacher mentions sounds like hocus pocus to me...
 

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Jorge,
I recently saw a program on the National Geographic channel (or was it PBS) where the commentator talked about the photography at National Geographic and how it changed the perceptions of people who read it since they always showed photographs of people from different cultures in exotic (to them) costumes and not of people going to work in a business suit(quite obviously).

You will be surprised how many times people here have asked me if elephants and snakes are common in India. My response has been - definitely, in zoos. :D
 

BobF

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Jorge, if its any consulation I felt she was getting ready to pray and it never occured to me that she would beg in that location.

Shesh, I was thinking about what might stereotype the US. Maybe towering rock formations and buffalo or bighorn sheep. The only problem is that I can find them all within a half hours drive and NOT in a zoo.

Bob
 

Shesh

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LOL, bob. Unfortunately, the stereotype of the US in India is regarding the people who are looked at as brash and loud. Most people are aware of the overwhelming natural beauty in this country though.

BTW, I envy your location - I've never been to CO.
 

BobF

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Shesh, this is fly over country suitable for photo opps only. Those brash Americans all live on the East and Left coast. :roll: (just havin fun all you Left Coasters)
 
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ader

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Thanks for your answers, I never realized i would start such a debate but most agree that H&D curves are for classroom only; to work out the tonal range of film and contrast of the film under normal conditions and normal processing. The old guy does have a certain "im master of photography realm" attitude but his images are actually quite plain jane...give me sarah moon any day.........and whom is bruce barnham and what is his book ? it appears he pops up quite alot in this forum........

thanks for your time,

ade (my fault but my name isn't "Ta" - "Ta" means thank you in england or Australia)
 

Jorge

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ader said:
Thanks for your answers, I never realized i would start such a debate but most agree that H&D curves are for classroom only; to work out the tonal range of film and contrast of the film under normal conditions and normal processing. The old guy does have a certain "im master of photography realm" attitude but his images are actually quite plain jane...give me sarah moon any day.........and whom is bruce barnham and what is his book ? it appears he pops up quite alot in this forum........

thanks for your time,

ade (my fault but my name isn't "Ta" - "Ta" means thank you in england or Australia)

Ah...sorry about the Ta, Ade... the attitude is not such a big deal but what I find inexcusable is that this guy is teaching and giving out the wrong information. I dont know what the circumstances are, if this is a college or just a workshop, but he should be challanged to explain his methodology after all he is not Moses spreading the word of God...no? :tongue:

Bruce Barbaum is an excellent photographer and is better known for his printing techniques. He is a regular contribuitor to Photo Techniques magazine and advocates the use of local contrats enhancement by using bleaching among another techniques. As Eric said, check him out his prints are beautiful.
 

inthedark

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May I please have more info on where to find Burnbaum's reciprocity tables. You mention a book, the title or even better the ISBN would be great. I didn't know Kodak's tables were wrong; I have been doing eveything by test as my cameras and work are so different, BUT I have been using those tables as a starting point. Sounds like I should upgrade to more accurate information.

Thanks,
JL
 

lee

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Jill,
I think that you may need to talk nice with Eric and Aggie for the receoprocity figures from Bruce Barnham. I took a quick peak at the website and did not see anything like that.

lee\c
 

Jorge

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I'll send them your way Jill.
The book is called the Art of Photography, an approach to personal expression. ISBN 0-8403-9647-3
 
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Jorge

How does one asks you nice??

:smile:

Jorge O
 
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