BTZS and low contrast scenes

[Jorge]

Jorge,

I had the opportunity to view both an example of your work and also an example of another photographer (who shall remain unnamed) pertinant to this thread in the traveling portfolio. I must say there is no comparison. Your print was outstanding. I wish that I could say the same about the other print. However, in good conscience I cannot do that. I was absolutely dismayed at what I saw in the other print, to be completely honest.

A "quick study" apparently does not equate to good prints. There is a vast disparity between "talking the walk" and "walking the talk". In other words anyone can spout jargon...not many can turn out good work.

As I have found in my life's experience...there has been nothing that has caused me more trouble as when I thought that I knew something when in fact, as I later found out, I didn't have a damned clue.

Thank you for the kind comment and you are not alone Don, I too have placed foot firmly in mouth many times...this is why I try to confine my posts to what I am sure I know reasonably well.

 

[Stephen Benskin]

I propose a test. Someone please take a picture, develop and print it. List the SBR, zone numbers or foot candles measured to evaluate the exposure. Project a range of values, then process to a given target value. List the film, developer and whatever numbers will show that theory and practice can be effective. Finally, print the film showing the results in a finished print. (Mike Pry's "early" BTZS pond picture comes to mind at this point, well done Mike) This would illustrate the question in terms more readily understandable than the jargon being bandied about.

Tim,

I'd have to disagree that this will be a good illustration of one system over another. The problem with a subjective test such as you've suggested is that there are too many variables involved to make a proper evaluation of the results. Flare for instance. It's next to impossible to measure in the field. Then there's the relationship between LSLR and LER. Not only does it generally depart from the concept of matching at the more extreme ranges, but a subjective interpretation of how well the negative matches the print is influence by the subject - its tones and tonal distribution. You also have statistics working for you. 68% of exterior scenes fall with in +/- 1 1/4 stops of the average luminance range of 2.2. This makes it hard to be too far off in most cases. And this is all in addition to the personal tastes of the photographer. It's incredibly difficult to yield an objective analysis from subjective tests (for example, The First Excellent Print Test).

Jones, L.A., The Control of Photographic Printing by Measured Characteristics of the Negative, JOSA, vol. 31, Oct. 1942.

Jones, L.A., Control of Photographic Printing: Improvement in Terminology and Further Analysis of Results, JOSA, vol. 38, n. 11, Nov 1948.

Jones, L.A., and Condit, H.R., The Brightness Scale of Exterior Scenes and the Computation of Correct Photographic Exposure, JOSA, vol. 31, n. 11, Nov. 1941.

 

[Stephen Benskin]

Forget it Jay...It's Chinatown.

 

[Jorge]

Forget it Jay...It's Chinatown.

It sure is, in more ways than one.....

 

[Kirk Keyes]

Your resume of my suggested technique is correct as to the method for determining exposure, but not for determining SBR.

Here is what I suggested. The scene is this. You use your incident meter and take readings, but regardless of where you point it you get the same EV reading, which suggests an overall SBR of 5. To compensate, do this. Record the SBR as 5 and then take another reading, covering the cone of the incident meter with your hand so that it does not see the sky. Record the EV reading and subtract it from the value that give you the SBR of 5 suggested earlier. This will give you the adjusted SBR that will be used to determine time of development.Sandy

THanks - I'll try this out sometime.

 

[Kirk Keyes]

I said: "You CAN develop film to a given SBR, just as you can develop film to a given CI."

This is a false analogy in my opinion. SBR refers to subject lighting conditions and is not in any way dependent on either exposure or development.Sandy

OK - but then Davis equates SBRs with G-bar (simplified CI) in his book and software. Look at the graphs he produces with it. Each film plot can display the G-bar value along with the associated SBR.

So is Davis wrong in placing these labels on his graphs? I think not - as he knows that in his system, a particular G-bar IS directly related to the SBR of the original scene.

CI is a slope created by minimum and maximum densities that is measured after development and results from both exposure and development.

I'll get back to you on this.

It might be ok to say that one can develop to an anticipated CI, but to say that one can "develop film to a given CI" when the final result is not the CI to which one is developing is not reasonable.

This is splitting hairs. It all really depends on your quality control as I described above. And does it really matter if you are off by a couple of 0.01 CI from your intended target CI?? And if you got achieved a CI that is slightly different than your target CI, then how can you say your blank film got a CI of zero, which you have.

CI has no reality beyond its realization. If you develop to a CI and get some other slope than what was intended then what you have is another CI.

What?? "No reality beyond its realization?" CI is a measurement of a property of film development. Please - let's not start discussing "reality" and "realization".

 

[Kirk Keyes]

Phil goess into this in his BTZS Lite. Metering for 2 dimmensional objects. I think that may help you here.

Mike, this is a software package?

 

[Kirk Keyes]

You are plotting a curve to find out average gamma, which you can then associate to a SBR value that you will obtain when taking a photograph.

Doesn't Davis use "average gradient" or G-bar, not "average gamma"?

And if Davis is graphing development time vs. average gradient, as well as dev. time vs. SBR, and dev time vs. N, then SBR is directly related to average gradient or N-development values. They are correlated through development time.

 

[Kirk Keyes]

Well the results of my knowledge are posted......anybody else wants to back up their claims with a final print?

Jorge - could you give a link?

 

[Kirk Keyes]

A "quick study" apparently does not equate to good prints. There is a vast disparity between "talking the walk" and "walking the talk". In other words anyone can spout jargon...not many can turn out good work.

Donald, artistic ability and technical knowledge are two separate things. Please don't confuse one for the other.

 

[Jorge]

Doesn't Davis use "average gradient" or G-bar, not "average gamma"?

And if Davis is graphing development time vs. average gradient, as well as dev. time vs. SBR, and dev time vs. N, then SBR is directly related to average gradient or N-development values. They are correlated through development time.

Didnt I write you could plot gradient vs sbr? did I in any way say they were not correlated in any way?

Does everything have to be a pissing match with you?......

 

[sanking]

I said: "You CAN develop film to a given SBR, just as you can develop film to a given CI."



OK - but then Davis equates SBRs with G-bar (simplified CI) in his book and software. Look at the graphs he produces with it. Each film plot can display the G-bar value along with the associated SBR.

So is Davis wrong in placing these labels on his graphs? I think not - as he knows that in his system, a particular G-bar IS directly related to the SBR of the original scene.



I'll get back to you on this.



This is splitting hairs. It all really depends on your quality control as I described above. And does it really matter if you are off by a couple of 0.01 CI from your intended target CI?? And if you got achieved a CI that is slightly different than your target CI, then how can you say your blank film got a CI of zero, which you have.



What?? "No reality beyond its realization?" CI is a measurement of a property of film development. Please - let's not start discussing "reality" and "realization".

Kirk,

This matter is closed for me, at least so far as it involves the merits of the case. If others want to continue the discussion with you that is their business.

However, please note that what Davis says in his book is absolutely irrelevant to the definition of CI, and equally irrelevant to whether or not a blank piece of film can have a CI, and also irrelevant to the concept of "developing to a given CI." CI was an established concept in literature of sensitometry well before Davis published the first edition of Beyond the Zone System. So for your discussion of the meaning of CI what Davis may or may not have written about the relationship between SBR and G-Bar is irrevelant, as is my opinion as to whether what he wrote is right or wrong.

Sandy

 

[Stephen Benskin]

Kirk,

However, please note that what Davis says in his book is absolutely irrelevant to the definition of CI, and equally irrelevant to whether or not a blank piece of film can have a CI, and also irrelevant to the concept of "developing to a given CI." CI was an established concept in literature of sensitometry well before Davis published the first edition of Beyond the Zone System. So for your discussion of the meaning of CI what Davis may or may not have written about the relationship between SBR and G-Bar is irrevelant, as is my opinion as to whether what he wrote is right or wrong.

Sandy

Kirk, I believe that exact phrase ,"developing to a given CI" was used in the authoritative paper published in the peer reviewed journal – Journal of Photographic Science Engineering.

 

[Donald Miller]

Donald, artistic ability and technical knowledge are two separate things. Please don't confuse one for the other.

Kirk, I certainly didn't confuse the two...but possibly you could elaborate on why one would not use technical ability, if it was in fact present, to produce work that evidenced technical proficiency. I would like to hear your reasoning on this.

Beyond that my discussion with you on this matter is finished. I guess that you and I will have to agree to disagree. I imagine that should not be a new experience for you.

 

[Stephen Benskin]

Kirk, I certainly didn't confuse the two...but possibly you could elaborate on why one would not use technical ability, if it was in fact present, to produce work that evidenced technical proficiency. I would like to hear your reasoning on this.

Beyond that my discussion with you on this matter is finished. I guess that you and I will have to agree to disagree. I imagine that should not be a new experience for you.

I don't think it's Kirk's responsibility to explain the concept of civility. Instead, maybe Don should look into some anger management classes and lots of sensitivity training.

 

[Jorge]

I don't think it's Kirk's responsibility to explain the concept of civility. Instead, maybe Don should look into some anger management classes and lots of sensitivity training.

LOL.....this from a guy sending insulting e mails.....

 

[Donald Miller]

I don't think it's Kirk's responsibility to explain the concept of civility. Instead, maybe Don should look into some anger management classes and lots of sensitivity training.

Stephen,

LOL ...this is really rich...coming from you...LOL If you care to...now, please understand this is a suggestion only, you might find it helpful to examine some literature dealing with psychological projection.

I will say that you have made some improvement because this time you didn't use the four letter word beginning with F in addressing me and you didn't email me, yet... I strongly encourage you to keep up your efforts because the results may surprise you. LOL

 

[Kirk Keyes]

Donald, Stephen, Jorge - if you would like to continue your off-topic discussion, please feel free to do so, in another thread.

And Donald, if you would like to start a thread on "but possibly you could elaborate on why one would not use technical ability, if it was in fact present, to produce work that evidenced technical proficiency", I would be really happy to join in on it. But keep in mind, I said "artistic ability and technical knowledge".

 

[Stephen Benskin]

You're right Kirk. It's not worth it. I've deleted my response.

___________________

Forget it Jake, it's Chinatown.

 

[sanking]

Kirk, I believe that exact phrase ,"developing to a given CI" was used in the authoritative paper published in the peer reviewed journal – Journal of Photographic Science Engineering.

I am perplexed as to why you believe this comment contributes to the discussion? The issue of whether the phrase "developing to a given CI" exists in the literature has not been in question, either in the previous thread or this one. So far as I can recall no one has claimed that the phrase does not exist in the literature. I certainly have not, and in fact I alluded to it in at least one previous message in this thread, for example where I wrote: “Even in cases where the term is used to in such a way that might suggest that it is a control or index number for processing, subsequent explanation always makes it clear that that CI is something to be obtained, not the process itself.”

Sandy

 

[Stephen Benskin]

I am perplexed as to why you believe this comment contributes to the discussion? The issue of whether the phrase "developing to a given CI" exists in the literature has not been in question, either in the previous thread or this one. So far as I can recall no one has claimed that the phrase does not exist in the literature. I certainly have not, and in fact I alluded to it in at least one previous message in this thread, for example where I wrote: “Even in cases where the term is used to in such a way that might suggest that it is a control or index number for processing, subsequent explanation always makes it clear that that CI is something to be obtained, not the process itself.”

Sandy

I probably just misinterpreted your comments.

 

[Kirk Keyes]

Kirk,

My connect is with the literature. I have looked carefully at the definition of CI in quite a number of technical books, including several devoted entirely to sensitometry, in order to better understand the issue, and I can find no example where the term CI, when defined, is not associated with a slope or gradient, which clearly shows that it is a result, not a process.

Even in cases where the term is used to in such a way that might suggest that it is a control or index number for processing, subsequent explanation always makes it clear that that CI is something to be obtained, not the process itself. I could agree that the phrase "to develop film to a given CI" describes a process, but the phrase does not redefine the meaning of CI. It describes only the reality of the phrase itself as something that takes place. And even within the context of the phrase in question the literature reaffirms the definition of CI itself as a result, i.e. a slope or gradient that defines two different points of density. Blank film, unless it is unevenly fogged, can not have two different points of density; it can not have a slope or gradient.

OK, I'm setting aside Davis. I’m satisfied with Sandy’s description of how to meter BTZS style for low contrast scenes. And I understand that Sandy is bowing out of the discussion – that’s fine.

Since I started this thread, I’ll take the liberty to officially hijack it and get back to my original contention about CI and blank film. See (there was a url link here which no longer exists) if you missed it.

Many opinions have been expressed that CI is dependant on exposure. It is not. They have infact gone on to tie this requirement for exposure to CI by saying if there is no exposure, there is no CI. That is wrong as well. And finally, there has been the claim that using the term/concept of CI as a level development or to describe a particular aspect of development, is incorrect or at least a perversion of the term. Let’s see.

I don’t know which technical literature Sandy was looking in – but I just grabbed a couple of them for here – “Photographic Sensitometry” by Todd and Zakia, and also the original paper on “Contrast Index”, published in the Jan-Feb 1966 issue of Photographic Science and Engineering, by C.J. Neiderpruem, Nelson, and Yale of the Kodak Research Lab.

So here’s a few quotes from Todd and Zakia –

“Gamma is the slope of the straight line of the characteristic curve.”

“Contrast Index is an average slope, as distinct from the straight-line slope specified as gamma. An average slope in this context is merely the slope of the straight line drawn between two defined points on the curve.”

As Sandy pointed out in the other thread, “Definitions of gamma, CI, and C-Bar always include the use of one of these two words, either slope or gradient.” And I DO agree. These are descriptions of the method of measuring the gamma or CI of a particular film. Let’s move on.

Also, for the rest of this discussion, keep in mind that when Todd and Zakia wrote this book in 1969, the term CI was quite new, and typically used the term “gamma” in instances where it would be custom to now use the term “CI”. They do say, “Recently the use of contrast index has come fro many purposes to replace gamma.”


CI is not dependant on exposure -

Todd and Zakia continue:

“[…] Gamma is a useful measure of the degree or extent of development. For this reason gamma is often used as a processing control index. If we want, for example, to maintain a replenished developer at a constant activity, we test this consistency by finding out whether or not the gamma, obtained from test strips, remains nearly the same. […] If gamma differs, we suspect that the difference is associated with the different degree of development, instead of with the factor we are really trying to test.”

Note that they say nothing about exposure here. They also flat out state that it is used as a process control index. That is a significant step beyond the simple definition of gamma or CI. In fact, it is an extremely useful definition, and allows a great deal of useful data to be applied to the act of developing film. The CI or gamma is not just a slope, it is a valuable property of processed film.

They continue, “Contrast index has the same uses of gamma: it is an index number that can be used for processing control purposes; when films (or developers) are compared, the test images should be developed to the same contrast index. Like gamma, obtaining a consistent contrast index will not insure all negatives will have the same total contrast, nor that all negatives will print similarly.”

Again they are using the term CI as a number, not as a slope. It is certainly derived from the calculation used to measure the slope associated with the definition of CI, but it is being used as a descriptive property of the processed film or processing.

They also did not require that the test films mentioned in the last quote, all have the same total contrast. This means that some films may have a larger or smaller level of total contrast. Some may have enough total contrast to actually perform a CI or gamma calculation – and some may not. Some may have half as much as needed, and some may be unexposed or completely overexposed. But is does not matter, as the level of exposure is an unrelated factor to gamma as will be shown in the next quote, and it is also unrelated to CI as well.

Todd and Zakia: “The value of the total negative contrast is dependant upon many factors. Among these are: subject luminance ratio; camera exposure level; color of light; gamma.”

Gamma and camera exposure level are two independent factors. They would not list gamma and exposure as separate issues if they were not. The same goes for CI as it does with gamma.

CI (or gamma) is not dependant on exposure.

If there is no exposure, is there no CI?

Now it was agued, that a sheet of unexposed film which has been developed for a period of time will graph on a horizontal line, i.e. at right angle to the vertical or parallel with the horizon - no slope, no gradient, and no CI.

This conclusion if false. Simply put, the math used to make this conclusion is incorrect. An unexposed sheet of film will give us one data point – written as a data pair - (exposure, film density). Since we understand that determining the slope or gradient requires a minimum of two data points, we should be able to understand that there is simply insufficient data to even attempt to draw any one line with only one data point. (Interestingly, there are an infinite number of lines that can be drawn through one data point.)

With only one data point, we simply cannot calculate the CI of this sheet of film. But this is not the same thing as saying that it has no gradient or CI as was claimed. The issue is there is just not enough data to calculate it here.

In fact, we don’t even need to have sufficient exposure in a frame or roll to have a film achieve a particular CI. (The film does have to be capable of actually achieving the CI, but any particular sheet or roll of film doesn’t have to have received some minimum amount of exposure to get processed to a particular CI.

Todd and Zakia say “In roll film, we may develop all the frames uniformly to a gamma of 0.75, but the negatives will no doubt have different total contrasts because of the variations in subject matter at least.” This also includes any blank frames or any overexposed areas – they mean the entire roll of film. They do not list any requirement for the number of points of density in the film because there is no requirement for this. Remember, both gamma and CI, are a property of the film development, and not the exposure. That entire roll of film they mention has a CI of 0.75, not just the parts with the “right” exposure. The blank parts have a CI of 0.75 too!

Please go back to the link I gave above and carefully read the example I gave of the step tablet that was being cut into smaller and smaller pieces. That entire sheet of film has a CI of some particular value, and even if we cut it into small bits, each of those bits still have that same CI. The CI of that film is an innate property of that film.

End Part I

 

[Kirk Keyes]

Part II -

Using CI as a term describing the development process -
Finally, as to the question of the use - whether the term CI (or gamma) can be used to describe a process, and not just the slope or gradient of a line derived from a film curve, Todd and Zakia have several examples of this type of use. Even my use of the phrase “to develop to a CI” was questioned. (Keep in mind that gamma and CI are interchangeable for the concepts described here. Sorry I don’t have any more recent references nearby.)

“In roll film, we may develop all the frames uniformly to a gamma of 0.75, but the negatives will no doubt have different total contrasts because of the variations in subject matter at least.” Develop to a gamma of 0.75, not for a gamma.

“We may, develop a negative exposed on a foggy day to a high gamma, say 1.5, and still have a flat negative because the subject has a small luminance range.”

“We may make a negative of another scene, with a large luminance range, develop it to a small gamma, and still have a negative of so great contrast that it requires a very soft paper for printing.”

“It is true that if we make two negatives of the same scene and develop them to two different gammas, we expect the negative developed to the higher gamma to have more contrast.”

“If we develop to a gamma of 0.5, the negative will have the same contrast as the subject for all straight line exposures. If we develop to a gamma of 0.5, the negative will have half as much contrast as the subject, but again only for the straight line.”

Let’s see what Nelson has to say: “For Film A, development to a gamma of 0.65 produces the desired range. However, developing Film B to a gamma of 0.65 produces a negative having a short density range.”

And here’s one where they use CI – “Using development to a contrast index of 0.56 (for portrait work) as the criterion for choosing the development times…”

I hope these are sufficient examples of the use of the term CI and gamma to describe a process or index value, and not just a simple result that is obtained by making measurements of the film curve. It is consistently used to describe the level of development to be given a film. It is a goal of the processing step, and not always an act of measurement of some piece of film.

You can see that there is no “suggestion” that the use of gamma and CI in these examples is as a term describing a control process, it is being used exactly for that description – these examples are way beyond mere suggestion. This is a “redefining” of the meaning - and one that has been in use for many decades.

Kirk

 

[smieglitz]

...But is does not matter, as the level of exposure is an unrelated factor to gamma as will be shown in the next quote, and it is also unrelated to CI as well.

Todd and Zakia: “The value of the total negative contrast is dependant upon many factors. Among these are: subject luminance ratio; camera exposure level; color of light; gamma.”

Gamma and camera exposure level are two independent factors. They would not list gamma and exposure as separate issues if they were not. The same goes for CI as it does with gamma.

CI (or gamma) is not dependant on exposure.


Kirk,

You are drawing an invalid conclusion. You cannot properly draw the conclusion that CI is not dependent on exposure just because your premise that gamma, CI, spectral properties, camera exposure, etc., are not the same thing. Doesn't follow.

If you reread what they are saying with an open mind, you will discover they are in fact discussing more than a single point whenever they discuss exposure in relation to CI or gamma. For example your quote of them:

“ In roll film, we may develop all the frames uniformly to a gamma of 0.75, but the negatives will no doubt have different total contrasts because of the variations in subject matter at least"

implies a subject with an inherent exposure variation ("variations in subject matter") instead of a single exposure value (as in a blank frame).


Did you ever consider that Todd and Zakia may have made an error of omission by not simply stating that CI (or gamma) was dependent on 2 (or actually 3 in the case of CI) data points? I would bet that they thought the concept of a measurement of slope (a contrast) was so straightforwardly dependent on two or more data points that they just never mentioned it. Nothing you have said above changes that fact.

You've not given any example by any of these sensitometrists where a variation/difference/contrast in exposure isn't implied in their discussion of developing a film "TO" a certain CI rather than "FOR" a certain CI. You are just choosing to overlook the implication that, for example, a portrait has many different exposures which have been taken simultaneously and from which one can develop TO a certain CI as well as FOR a certain CI and derive the measure. Nowhere have you *proven* a blank frame can be developed TO a certain CI.

And why do you choose to dwell on this totally impractical and irrelevant point??? B-O-R-I-N-G. You can go on with this if you wish but I too have had enough of this absolutely meaningless debate.

Go take some pictures or pay your taxes or something.

Later.

Joe

 

[Jorge]

You know, getting out the books and quoting those passages that only support your argument and dismissing the rest is really a silly way to argue.

Now that you have quoted Todd and Zakia, I decided to go get my book out and quote them. Here is their definition for contrast index:

Page 71 Photographic sensitometry:

"Contrast Index is an average slope. An average slope in this context is merely the slope of the straight line drawn between two defined points on the curve. Since the value of the slope will vary with the points that are chosen, some decision muxt be made about the definition of the two points"

Since your blank film has no curve and it has no two points, you have no CI in a blank piece of film as quoted by your sources. QED.

And yeah...I agree with Joe, you are not showing that you are smarter than all here, only that you are a greater PITA.....