Well for what it's worth I've learnt a lot from your threads and hope you keep posting even if some people mouth off.
There is always going to be detractors. I just wish there was more participation in general. There are a lot of smart people on APUG, so the only conclusion is there is a lack of interest on these topic. If people were interested and didn't understand something, would they be asking questions?
I'm glad at least a few people are interested. Michael, you should jump in more. These discussions can really benefit from someone with your experience.
BTW, I believe the posts in the K factor thread are the only time I've ever seen an attempt at connecting the dots between all the different aspects of exposure. In the way information is generally presented, there is a tendency to break concepts down into smaller parts in order to get a handle on them, but then it's hard to see how everything fits together. That's one of the reasons I did the four quad program. Most people work with the film curve and paper curve as seperate objects, and completely leave out the camera image curve. This makes it hard to understand how all the elements of the photographic process interconnect. Concepts become disjointed like the ZS NDR and the paper LER.
I'd like to think the film speed / metered exposure ratio thread connected a few dots too, but without anyone participating how well were they communicated? Maybe with some more feedback, those concepts can be better and more clearly defined.
Last edited by Stephen Benskin; 02-08-2012 at 06:06 PM. Click to view previous post history.
Sorry, I typed that last post at work. That last part should read that "without any participation it's difficult to gauge how well the concepts were communicated."
I’ve been reviewing some old papers and I’ve run across something interesting. While the concept is one that is very familiar, it is expressed well. It comes from a paper by Allen Stimson, Measuring and Judging Photographic Exposure of Color Film for Automatic Exposure Controlled Cameras.
“Correct exposure can be judged from the appearance of a color transparency, although it may be evaluated differently by different people. Each observer thinks the correct exposure is that which he prefers. If different exposures of the same scene are judged by several observers, the one preferred by the majority is called the ‘preferred picture exposure.’ The exposure that will be preferred cannot be exactly predetermined, and different observers may not agree closer than +- 1 Ev.
On the other hand, exposure within +-0.5 Ev of the preferred picture exposure can usually be predetermined by photometric measurements of a scene quite satisfactorily for most amateur work. An experienced photographer can often improve the indicated exposure by judging the brightness of the subject in comparison with the general scene conditions measured by the meter, although for many types of scenes, he cannot know in advance the lightness or darkness of the subject matter which will best express the desired mood. Consequently, in important situations, he will make three exposures to bracket the range indicated by the meter.
It is necessary to recognize this fundamental difference between photometric measurement of exposure and preferred picture judgment of exposure. One is foresight while the other is hindsight; the former can be precisely measured and expressed in numbers, while the latter can be found only by judging finished pictures. The two are equal for the statistical average scene.”
And from later in the paper:
“It has been found that, in judging a sequence of identical pictures having different exposures, observers may differ in their exposure preference for some types of scenes by as much as +-1 Ev. They usually disagree on scenes of lower contrast.
A film may be judged to be overexposed when the sky area loses its color or when flesh tones appear to be washed out. It may be said to be underexposed when the area of greatest interest to the observer is darker than preferred. These criteria are often related to the photometry of the scene only through statistics.”
And this is with the small tolerances of color reversal film. Think what the range of preferred picture exposure is with black and white negative film means. Then consider the practicality of the concept of correct exposure, or maybe consider what having a difference between a photometric correct exposure and a preferred picture exposure. Finally, what does this say about an individual’s anecdotal observations about the effectiveness of their personal exposure methodology? Perhaps for their conclusions to have any real validity, they should be evaluated from both the photometric exposure and preferred picture exposure perspectives.
Last edited by Stephen Benskin; 02-08-2012 at 11:39 PM. Click to view previous post history.
I do find the discussion interesting and I've gotten some great ideas and appreciate the info you have provided Stephen.
There are certain limits though in applying the ideas, what I mean by that is that it has to fit into the larger context of taking and printing a photo.
For example I actually find the biggest practical challenge in judging and getting good exposure is not in how to get a single SBR exposed well, but in how to get competing SBRs (subjects) to fall properly in relation to each other on the film so that they will fall properly on paper.
The question for me is not just how do I get what's in front of me but, how do I manipulate the scene to get what I want?
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Anaïs Nin
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I like to think of it as similar to what people who know the Zone System or Beyond the Zone System tell those who are contemplating learning the methods. It takes effort at first to understand it, but it will eventually free you up creatively.
Last edited by Stephen Benskin; 02-09-2012 at 06:50 PM. Click to view previous post history.
I do agree Stephen. Understanding enough pieces of the puzzle allows us to concentrate on other things.
That's not where we start though, we learn/refine the pieces we go.
Creatively we always get to a result, the difference in understanding and not, is simply whether we can repeat things reliably or not.
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Anaïs Nin
This is a bit of a coincidence. I just found a paper I’d copied years ago and then forgot about. It not only fits the topic of this tread. It was hiding in plain sight, but it also addresses some of the questions that have arisen here; and I’m not even finished reading it yet. The paper is from D. Connelly, The Specification of Conditions for the Incident Light Method of Exposure Determination.
These two excepts have so far stood out.
“It is of interest to note that the manner of determination of the constant is not a photographic one. The assumption is made that if an exposure meter is adjusted first so that it gives satisfactory information about photographic exposure (by using it and adjusting it to give satisfactory photographs) and is subsequently tested as above to determine the constant then the constant and the ability to provide correct exposure information are related consistently.”
And about distinguishing the two values of C:
“The way in which exposure meters should be used for either the reflected or the incident light methods is not given directly in the specifications [standards], but it can be inferred from the methods given for their calibration and checking. For calibration of the meter for the reflected light method its photo-cell is subjected to illumination from a screen having uniform brightness. This is a sufficient condition to ensure that the calibration and subsequent use of the meter are similar.
For calibration of the meter for incident light method the meter, together with whatever light pick-up device is used, is subjected to illumination from a point source of light situated on its optical axis. A reasonable inference from this condition might be that in use the exposure meter with pick-up device should be directed towards the source of maximum illumination. In practice, as has been noted previously, the recommendations include aligning the exposure meter axis with the direction of maximum illumination, or aligning it with the camera axis or doing both of these things and finding an average.
Here the calibration conditions and the manner of use are not necessarily similar, largely because of lack of information in the specification. It can be inferred that the type of pick-up which it is intended should be used is that which at the time the specification was issued was most prevalent, and on this basis it is presumed that a flat translucent screen placed over the photo-cell of the meter is the requirement.”
Happily and surprisingly, this supports what I hypothesized back in post #44. The difference between the old single value of C and the modern cardioid value of C was just about equal to the ratio between the two modern versions of C.
This paper was published in 1963. As far as I know, the first standard to have a distinction between the cosine receptor and cardioid receptor wasn’t until 1974.
I hope the rest of the paper is as interesting.
Last edited by Stephen Benskin; 02-10-2012 at 07:52 AM. Click to view previous post history.
I don't know, Stephen, based on most of what I've seen and read, while it takes some effort to understand it, in fact very few people are freed by it. They don't know how to use it, and they don't consider enough of the end to end process from taking stage to print. They apply formulas to the negative, and believe that is the way to a fine print. Witness all the crap out there about shadow placement, contractions, stand development myths etc. Most people have no idea what is actually going on with the negative, and it is evident in the prints (at least many of the examples I've seen). What's worse is often people don't even see the results. They think they see something, based on what they've been told should be there (by people like Barnbaum and many others).
Originally Posted by Stephen Benskin
Regarding my participation in these threads, I'm more active on some of them than others, mostly because I don't always have the background necessary to discuss them intelligently. I don't always understand all the formulas and terminology so I leave it to you and (mostly) Bill Burk to hash out. But I'll try to contribute more actively where I can. As I've said, I find these threads to be, probably, the most value-add on APUG.
Thanks. That's very kind.
Originally Posted by Michael R 1974
My favorite is the rumor that Alan Ross has discovered a negative density range of 1.45 for normal. That one always makes me laugh. If there's nothing else I've gotten out of studying theory it has to be a pretty good BS meter.
What's worse is often people don't even see the results. They think they see something, based on what they've been told should be there (by people like Barnbaum and many others).
Seriously, we all learn in stages, and it's hard, if not impossible, to see beyond to the next stage. We probably all have to go through the "Mr Photo said this" and "I've heard about that" stage. We also tend to learn only when we are ready to learn it. The number 42 from Hitchhikers Guide to the Galaxy has little meaning unless you are ready to understand the question. (This thread is kind of about that point.) We all have to first earn the rules before we can begin to understand their limitations, tolerances, nuances, and variances. Some are comfortable just understanding the rules of use, which is fine. Some aren't.
For me, I was working in a photo lab and wanted to understand more about what I was doing. I read all the books I could get my hands on, but most of the ones knew about or could find weren't specific enough, then Jack Holm sent me a paper he had written. It had many of the specifics I was looking for including exposure equations, and more importantly it had a bibliography of other source materials. Papers that explained the thought processes that lead to the equations in Holm's paper. His paper and bib opened up a whole new world. But as my math skills suck, it didn't turn out to be a speedy journey of discovery.
That's one of the reasons why I give my sources and upload papers. It's also one of the reasons why I participate on this forum. You never know what that trigger could be. But it can be hard at times dealing with the Alan Ross rumors.
Last edited by Stephen Benskin; 02-10-2012 at 09:27 PM. Click to view previous post history.