Test for Pyro Negatives on Graded Silver Paper

[sanking]

For a very long time Steve Simmons and I have had a fundamental disagreement as to how the stain affects printing with graded silver papers. Steve holds that stained and non-stained negatives can not be developed to the same effective printing contrast. I disagree. Here is a fairly simple test that any interested party could to see which of us is right. It must be done with graded silver papers, not VC papers.


For this test you will need the following. A 21 step Stouffer (or Kodak) transmission step wedge and a few sheet of graded silver paper. Any grade will work, including any grade of AZO. You will also need at least one staining developer and one other developer, either staining or non-staining. If you have both PMK and Pyrocat-HD you could use them since this comparison is what sparked the present discussion. You will also need a light source that can be timed to 1/4 or 1/2 second. An enlarger with a digital timer with accuracy to 0.1 second will work fine. You will also need some print developer for your paper.

Please note. You must use graded silver papers for this test, not variable contrast papers. Variable contrast papers will indeed print differently in the highlights depending on the color of the stain.

Step 1 – Use whatever film you like. Take the transmission step wedge and contact print it to a sheet of film of whatever size is convenient for you to process. I do most of my testing with a Stouffer TP 45 step wedge and contact print onto 4X5 sheet film. This initial step will require some testing to get exposure in the ball park, but if you set your enlarger at a height needed to make about an 8X10 print from a 6X6 negative the exposure should be in the 0.5 second range at somewhere between f/5.6 and f/22. What you eventually want is to expose the test strip in such a way that when it is developed for about 12-14 minutes all but two or three of the steps will have some density. But at least two of the steps should just have B+F density for this test to work as designed.

Step 2 – Once you have determined a basic exposure time for your film, expose two or three sheets identically, i.e. same time and f/stop. Develop one in Staining Developer #1, whatever that is, another in either Staining Developer #2, and perhaps a third in a non-staining developer. This could be a PMK to Pyrocat-HD comparison, or a Pyrocat-HD to D76 comparison, or perhaps you may want to compare PMK, Pyrocat-HD and a non-staining developer such as D76 1:1.

Step 3 – Develop all three sheets of film for the same time, one in each of the developers. You don’t really know how much time each should be developed at this time, so let’s just arbitrarily say each should be developed at this point for 14 minutes at 72F.

Step 4 – When the step wedge negatives are processed and dried, you should now contact print them to graded silver paper. Use your enlarger light source, or if you print with AZO, whatever light source you use with this paper. It does not matter what kind of light source you use, but since the light source affects spectral sensitivity it should be the same for all three tests. You could use any grade you want, or AZO, but I would suggest a #2 paper so the numbers I am about to use will make sense. In making the prints you should expose each so that the last two steps, #20 and #21, print maximum density. Be very careful in exposing so the comparison prints looks exactly the same at Steps 20 and 21, and Step 19 should show just slightly less density. Careful reading of maximum density is critical for the later accuracy of the tests so make sure you get this right.

Step 5 – Evaluate the prints. Chances are that development was such that the step wedge prints do not all have the same effective printing contrast. For a graded #2 silver paper you should have a ES of about log 1.05, which is 7 steps, since each is log 0.15. As you know, this is an exposure scale of 3 1/2 stops, about right for graded #2 silver in contact printing. Look at the three test prints and see if one of them has a range of about 6-9 steps. Let’s assume that your print made from the PMK negatives has exactly 7 steps, the one from the Pyrocat-HD negative has 9 steps, and the one from the D76 1:1 negative has five steps. The PMK negative would be considered standard as it is correctly developed, the Pyrocat-HD negative is under-developed, and the D76 1:1 negative is under-developed.

Step 6 – Repeat the tests with Pyrocat-HD and D76 until the effective printing contrast is the same for all three negatives. In the above situation you will need to develop the Pyrocat-HD negative longer, and the D76 negative less. Visual analysis of the negatives, or even a densitometer reading, will not help you in this comparison since the stained negatives have more effective printing density than you see. However, eventually you will be able to match the prints so that all three negatives print with the same range of tones, from the shadows to the highlights. At that point, if you were to read the reflected densities of the three step prints and plot the curves, they will overlap.

Step 7 – Take your tests outside and make a few identical exposures of a scene. In the darkroom, develop each for the time required as determined by the above tests. If you have done a good job in testing the negatives , stained and non-steained, will print with exactly the same contrast

And now you know the truth, i.e. if you match the effective printing contrast of your negatives by adjusting time of development, there will be no difference in the way tonal values are reproduced, not in the shadows, not in the mid-tones, and not in the highlights. And that is true whether the comparison is made with two staining developers, or if it is made with one staining developer and another non-staining developer. Essentially, whether you use a staining developer or a non-staining developer it is possible to adjust time of development so that each will print with the paper ES.

This test asssumes that the developers used are non-compensating, and that is true in the case of PMK, Pyrocat-HD and D76 1:1 with graded silver papers. Both PMK and Pyrocat-HD provide a compensating effect with VC papers.

Try this test and report your finding.

Sandy King

[steve simmons]

"Steve holds that stained and non-stained negatives can not be developed to the same effective printing contrast."

Thks is a mis-statement of my position.

What I have said is that developing two negatives with different staining developers to the same CI will not necessarily result in the same tones on the same grade of apepr or with the same contrast filter with VC papers. This is why I advocate the min time for max black process that Fred Picker described about 29 years ago.

When I compared PMK and Pyrocat with two films a couple of years ago I worked out dev times to get matching zone 8 tones on my paper. I used vc paper but the trest would be the same with graded papers. This is what Sandy is advocating above when he suggests that you keep testing dev times until the different developers produce matching results.
What is 'effective printing contrast'? IMHO it is getting the upper range tonal values that one wants in their prints. Apparently Sandy has dropped the concept of matching CI which he criticized me for when i did my test. I was scolded for not getting matching CI. Now the term has changed to effective printing contrast. This is different than CI.

This debate has become a floating game of change the rules. Sandy has manipulated the concepts and terms to the point that he now agrees with me and the way i tested in my article a couple of years ago.


Secondly, there appears to be a position in his post that two negs with the same 'effective printing contrast' that the prints will match each other. This is patently false. If that is the case why do we both encourage the use of staining developers and why did he create his special formula? If a non-stainigng developer will do the same as a staining developer if they are both developed to the same effective prionting contrast' than we can all use one non=staining dev and get the same results.

This debate is going in circles because the rules keep changing.

Let's see what we agree on.

1. Staining devlopers offer several advantages. I am making this assumption not from this thread but from previous threads. If I am wrong I apologize.

2. If you use different developers, staining or not, you need to probably use different dev times to get the same effective printing contrast. This has been my piostion all along and this validates the way I tested two years ago. I used different development times with FP4+ and PMK and Pyrocat to get the same zone 8 tone on my prints (the same effective printing contrast). Matching CI is not the way to go becasue the color and density of the stain, primarily in the high values, will be different for different developers.

I hope this exchange has been helpful to others.. It has helped me understand Sandy's position which seems to have evolved to agree with mine.

Lets end this debate and go take pictures, go fising, bike riding, etc.

steve simmons

[sanking]

"What I have said is that developing two negatives with different staining developers to the same CI will not necessarily result in the same tones on the same grade of paper . . . "

I believe that is how I stated your position.

I have abolutely not dropped the concept of matching CI, but I am saying now, and have said for a very long time, that a CI as measured by densitometry and plotted would not provide the same effetive printing contrast of two stained negatives where the color of each is different. That should be pretty much self-evident. And I have never said othewise so please don't mis-represent my position. It may be that when your test first appeared some people expressed the view that the effective printing contrast could be precisely established through sensitometry, but that has never been my position. I would say that sensitometry could be used as an initial guide to help us zero in on effective printing contrast, but in the end the use of step wedge prints is the only completely reliable way of measuring printing contrast with stained negatives.

You ask, what is the same effective printing contrast? It is when you can exactly match exposure scale on the same paper with two differnet negatives. And that would involved more than just matching Zone VIII densities. It means an absolute, or close to absolute, match of each density of the step wedge, from Dmax through the highest highlight density of the step wedge.

Putting those issue aside, there is still one area where we have fundmental disagreement, and that is the issue that can be resolved by the test I propose, if you or someone else want to put it to the test. You say, "there appears to be a position in his post that two negs with the same 'effective printing contrast' that the prints will match each other. This is patently false. If that is the case why do we both encourage the use of staining developers and why did he create his special formula?"

This is in fact our most fundamental disagreement. I did not say that the prints would exactly match each other. There are, after all, other issues of importance such as grain and sharpness. What I have said, and am saying, is that the prints from stained and un-stained negatives will exactly match other in the way tonal value densities are reproduced, all the way from the shadows to the highlights, if the two types of negatives have been developed to the same effective printing contrast. I have done tests with graded silver papers comparing stained and non-stained negatives, and when the negaties have the same effective printing contrast you can map values from Step 1 to Step 21 so that they print with identical density from each type. So you believe this is patently false? Well, just try it and see what happens. Or better, perhaps someone else whose credibility on this is not on the line will test it and report back. This is definitely something that we will be doing in the study on Pyro developers that is being planned.

And you ask, "Why would we recommend Pyro developers if the above is true?" Well, perhaps because they are sharper and print with less grain because of grain masking. Is that not enough? Pyro stained negatives have a unique compensating effect with VC silver papers, but that effect does not exist with graded silver papers, including AZO, and it does not exist with alternative processes. To claim otherwise is to perpetuate a myth that can can be easily disproved. Howard Bond already disproved it in the article in DT. What you are claiming simply is simply not factual, and no amount of bending the truth will make it so.

That is all I have to say about this. My position has been stated very clearly, and I have presented a testing procedure that any reasonably talented silver printer could follow to test the validity my conclusions.

Sandy

[sanking]

“I hope this exchange has been helpful to others.. It has helped me understand Sandy's position which seems to have evolved to agree with mine.”


I would agree that some of our discussions of this past evening, and in this thread, have been useful to me as well in understanding’s Steve’s position. Up until this past evening much of my thinking was predicated on the assumption that we agreed on how silver graded papers would print with stained developers. It never crossed my mind that Steve sincerely believed that the use of stained developers in combination with graded silver papers offered some advantage over non-staining developers in terms of how highlight detail is reproduced, as they do with VC silver papers. Now that the basic point of conflict has been clarified, there should be some resolution of the issue, because there is a simple testing procedure to determine whether he is right or I am right about this.

I hope this is the case. I am very tired of this continuing feud and would like to see it end. I have a lot of respect for Steve Simmons for his work in publishing View Camera (I have been a subscriber since the second or third issue of the magazine) and in promoting the View Camera conference, and for other important contributions to the LF community. To illustrate the importance of those contributions, let me remarkd that I initially met one of my best friends in the LF community at the first View Camera conference.

Also, there is no question but that Steve Simmons and I agree on about 95% of the important things about printing with staining developers. I hope that both of us will find a way in the future to emphasize our areas of agreement, and possible areas if of collaboration, than the negative.

Sandy King

[steve simmons]

From King


"if you match the effective printing contrast of your negatives by adjusting time of development, there will be no difference in the way tonal values are reproduced, not in the shadows, not in the mid-tones, and not in the highlights. And that is true whether the comparison is made with two staining developers, or if it is made with one staining developer and another non-staining developer. "


“What I have said, and am saying, is that the prints from stained and un-stained negatives will exactly match other in the way tonal value densities are reproduced, all the way from the shadows to the highlights, if the two types of negatives have been developed to the same effective printing contrast.”


These statements are patently false but are the diehard belief of the sensitometrists. The PMK and Pyrocat negs I did were developed to the same ePC but the prints did not match. Sandy's test has no value if the above statements were true. He want to show that a contrasty scene, at least that is where this debate started, developed in Pyrocat would produce a better print and is worth the extra trouble of stand development when compared to a PMK neg simply developed in the normal tray manner for just less time. If we develop to the same EPC and the negs produce the same qaulity of print then his developer and special process is no better than PMK with a neg just developed for less time. If he is ready to concede that he believes the above two statements then such a test is moot. In that case he admits I can do the same with PMK and just shorter development that he can do with Pyrocat and stand development.

I have asked people like Hutchings, Alan Ross, etc. to participate here but when they see King's locker room slurs and name calling they just go off and do somehing else. Perhaps Sandy likes the bully pulpit. It keeps other knowledgeable people away and, he hopes, the 'expert' chair to himsel;f. However is inconsistent statements in these two threads belies his status as truly understanding staining evelopers. In fact I am even beginning to doubt his understanding of black and white printing and how black and white prints are influenced by negative processing.

steve simmons

[sanking]

Steve,

I have described a basic test that will test the premise in question. Some people will no doubt take up the challenge, and then the truth in this matter will become evident to all when they report their results. How you chose to deal with this is up to you, but I don't believe name calling and more insults will be of much use to you at that time.

As I have stated before, the issue has already been resolved by Howard Bond in his article in DT. I suggest you read it carefully, especially the part about graded silver papers.


Sandy

[sanking]

I think it is a pretty sad state of affairs to see a person of Steve's category resort to character attack rather than just dealing wiht the issues. This does not bode well in my opinion for the future health of View Camera. Editors should keep an open mind on issues and avoid degrading people simply because they have a difference of opinion. If something is false it will still be false after a thousand repetitions, no matter how loud it is shouted.

As for this constant complaint about the locker room comment, I have posted thousands and thousands of message to a variety of photogaphic forums over the years. Most people would agree, I believe, that my posts, with the exception of a handful, have been polite, to the point and informative, and have not used vulgar language. Before Steve gives me advice on how to communicate with the forums he might want to look in the mirror first. I would also suggest he spend more time on improving the quality of his magazine, or perhaps sell it to someone who will.

As for the specifics of this discussion, I have mentioned several times an article by Bond in which he compared staining and non-staining developer, with both VC and graded silver papers. The article is entitled, "Pyro Revisted" and can be found pp. 23-26 in the September/October issue of Photo Techniques.

In his article Bond used four films (Tri-X, T-Max 400, FP4+ and HP5+), and developed all of them in both PMK and WD2+, and in D76 (Kodak films) and DD-X (Ilford Films). In the article Bond tested with transmission step wedges and provides both real prints and plots of the curves. I quote from a part of the article pertinent to the present discussion. "For figure 5, the same PMK films print was printed ion graded and VC paper. The graded paper saw the stain as neutral density and its curve shape was not affected. The result was similar to printing a D-76 film print on VC paper, as shown in figure 4."

Bond's article is the model for anyone interested in conducting comparision tests of staining and non-staining developers, and I plan to draw extensively from it in designing the parameters of my own testing. Bond's article is by no means totally negative about pyro stained developers. He acknowledges, for example, that several of the films tested showed greater apparent sharpness in the pyro developers.

When it comes to where to stand on the issue of how graded silver papers print with stained negatives, I am proud to rest my credibility and reputation on views that are in very substantial agreement with those of Howard Bond, whose reputation as a printer is far greater than that of either Steve or me. And his article is based on sound methdology, well written and illustrated, and reaches many valid conclusions, including his comments about printing on graded papers with stained negatives.

Sandy

[Jay DeFehr]

There are some obvious falsehoods and misconceptions above that should be pointed out-


You ask, what is the same effective printing contrast? It is when you can exactly match exposure scale on the same paper with two differnet negatives. And that would involved more than just matching Zone VIII densities. It means an absolute, or close to absolute, match of each density of the step wedge, from Dmax through the highest highlight density of the step wedge.

The above implies that a given CI produces a given curve shape, which, of course is fundamentally untrue, and anyone with even the most basic understanding of sensitometry knows it to be so. When two developers that produce different curve shapes are being compared, it is entirely practical to match their curves at a strategic point of interest, like Zone VIII.



Pyro stained negatives have a unique compensating effect with VC silver papers, but that effect does not exist with graded silver papers, including AZO, and it does not exist with alternative processes.

The above implies that any compensation effected by a staining developer is attributable strictly to the stain, which is, of course, not true. It is entirely possible that one staining developer effects compensation, while another does not, and that the effect would be discernible on graded paper, and all of the name-dropping and credibility piggy-backing in the world won't change these facts.

Jay

[sanking]

The above implies that any compensation effected by a staining developer is attributable strictly to the stain, which is, of course, not true. It is entirely possible that one staining developer effects compensation, while another does not, and that the effect would be discernible on graded paper, and all of the name-dropping and credibility piggy-backing in the world won't change these facts.

Jay

OK, but neither PMK or Pyrocat-HD are compensating developers when printed on graded silver papers, at leat not when used in the recommended dilutiions. If yo look at a curve of print densities from these three types of negatives on graded papers you will see no compensation.

I assumed you would have understood that I would have thought of that issue.

Of course, if you were to use either PMK or Pyrocat-HD in more diluted working solutions you might get some developer exhaustion and highlight compensation in the shoulders of the curve. But that does not happen with these developers when used at the recommended dilution and in the correct amount.

Sandy

[Jay DeFehr]

You didn't address curve shape vs contrast.


It is when you can exactly match exposure scale on the same paper with two differnet negatives. And that would involved more than just matching Zone VIII densities. It means an absolute, or close to absolute, match of each density of the step wedge, from Dmax through the highest highlight density of the step wedge.

Assuming, as you do, that all three developers produce the same curve shape, it should only be neccessary to match two steps on the stepwedge, and all the other steps will overlap. So if one matched the steps that correlate to Zones I and VIII, or III and VIII, that would constitute a common "Effective Printing Contrast", by your definition. Isn't that what Steve did, in essence?

What about local contrast; how do you measure it with a stepwedge? Does it affect curve shape? Could it affect the appearance of tonal separation in a print? How about sharpness; can the appearance of sharpness effect the appearance of tonal separation in a print, without affecting the densities of a stepwedge?

Youve been quick and enthusiastic to criticize Steve, his testing, and conclusions, but it seems to me that by your own standards, Steve did everything right, except for sharing your developer preferrence.

Jay

[Jorge Gasteazoro]

What I have said is that developing two negatives with different staining developers to the same CI will not necessarily result in the same tones on the same grade of apepr or with the same contrast filter with VC papers. This is why I advocate the min time for max black process that Fred Picker described about 29 years ago.

And this is why you are fundamentally wrong in your testing. When you measure something you need to use the same tape measure, you cannot use one mark with cm and another in inches to compare the same thing. It works the same in photography, you can only change one variable to make comparisons.....you fail to understand this and as such your testing is flawed. Max black from min time cna be used with some modifications but not the way you use it.

[j.e.simmons]

Max black from min time cna be used with some modifications but not the way you use it.

How, then, can it be used?

juan

[steve simmons]

Even Sandy agrees that if you take two staining developers and dev negs to the same CI you will not get prints with the same range of tones. This is especially true with staining developers and vc paper becasue the color of the stain has a big influence on the contrast and what light gets through and exposes the paper. Even Sandy agrees, now anyway, that the best test is to get EPC and than make the print. Doing CI curves and matching with staining developers is just an academic exercise. Go back and read the two threads and you will have a lot more useful inofrmation.The min time for max black gives you EPC and is just how Sandy now wants to test.

steve simmons

[robert]

does anyone have a link to Bond's article? thanks

[sanking]

does anyone have a link to Bond's article? thanks

So far as I know this article is not available on the web. It is not on Howard Bond's home page, and it is not one of the articles that you can download from the PhotoTechniques archive, at least not that I can see from a look at the site.

However, I would assume that PT can provide you with a copy of the article, or a backcopy of the issue.

Sandy

[Jorge Gasteazoro]

How, then, can it be used?

juan

Very simple Juan, instead of using minimum time for maximum black, you use minimum time for Zone V tone. This way you anchor a value that will give you a family of curves within a chosen paper. If you then change contrast you still have information. The way Simmons uses it, he can only use one contrast grade and if he changes, he has to do all the tests again. Furthermore, if you change papers, all you need to do is print one step tablet to see how the contrast changed, not so with the way SImmons does it. Of course, when he is told this, he does not understand the underlying sensitometric principle for this and insist this is wrong.


Even Sandy agrees that if you take two staining developers and dev negs to the same CI you will not get prints with the same range of tones

This is wrong, it will not give the same tone distribuition but it will give you the same range of tones. Please learn to use the language of photography if you plan to continue to argue this.

[steve simmons]

We are posting detailed instructions on how to do the Minimum Time for Maximum Black Film and development Time Test in the Free Articles section of our web site. Fre Picker first described this procedure in his book The Zone VI Workshop. It was a welcome relief to Ansel's first series of books whach many people were unale to put into practical use.

I have tested many ways including this procedure and with densitometers. I always end up needing a density of about 1.35 above film base plus fog for my zone 8. I have done this on graded papers 20 years ago and on vc papers in the last few years. You can get their both ways of testing and it will work with staining and non-staining developers.

It is important to get enough exposed density on the film to get the desired shadow values and enough developed density in the high values, for me zone 8 but some people use zone 7, to get the desired high value tones. This test is aneasy and straight forward procedure.

This article should be up later today.

good luck


steve simmons

viewcamera.com

[Jorge Gasteazoro]

I have tested many ways including this procedure and with densitometers. I always end up needing a density of about 1.35 above film base plus fog for my zone 8. I have done this on graded papers 20 years ago and on vc papers in the last few years. You can get their both ways of testing and it will work with staining and non-staining developers.

Yep, and you have obtained wrong results for 20 years too....like PMK giving greater speed with film than Pyrocat HD, something anybody who has done the correct testing knows is wrong. But then, propagating wrong or incomplete information seems to be something you are good at.

[steve simmons]

"Even Sandy agrees that if you take two staining developers and dev negs to the same CI you will not get prints with the same range of tones

This is wrong, it will not give the same tone distribuition but it will give you the same range of tones. Please learn to use the language of photography if you plan to continue to argue this."



You need to go back and read his posts. He and I are in agreement. This is becasue the different staining developers will have different colors of stain and will affect what parts of the color spectrum of light reach the printing paper. VC papers are especially sensitive to the color of the stain and graded papers are less so.

I would encourage you to use a variety of resources in getting information. There are some here who are dedicated to promoting some mis-information and their behavior keeps some very knowledgeable people form participating on this forum. If you have questions about staining developers and want aanother resource beyond this forum try looking around for other forums. There are several available on the web.


steve simmons
www.viewcamera.com

[Jorge Gasteazoro]

You need to go back and read his posts. He and I are in agreement. This is becasue the different staining developers will have different colors of stain and will affect what parts of the color spectrum of light reach the printing paper. VC papers are especially sensitive to the color of the stain and graded papers are less so.

Once again, you show your lack of understanding. Tonal distribuition and tonal range given by different developers are a function of the developer and the film only and has nothing to do with the paper used to print them. On the other hand if you are talking about the reproduction cycle then you would be correct, but then this is why graded paper is used, so that the color of the stain is one more variable that is held constant when you are doing film/developer tests comparisons.

This of course is something you have failed to understand all this time we have tried to explain this to you. I would take your own advice and try to educate yourself a little bit more. Remember, I know how to use your silly little test and have identified the flaws inherent to it...you dont know how to do what I do, which is very evident in your posts here. So please, if you are going to continue to argue, try to use language that is specific enough, hell english is my second language and I can do it, why cant you?

[steve simmons]

what is the tonal distribution?

what is the reproduction cycle?

Perhaps I should ask a biologist about the second one. These are not photographic terms. Where did you get these terms?

Perhaps this is why we can not communicate. You are using terms that are not photographic and rather unique to you.

What about people who use vc papers?

You have to key your neg exposure and developement to your paper. That is where the neg is going. Ansel knew this many, many years ago so I do not know why we are rehashing a very old wheel.That was the genius of Picker's book. It keyed the density range of the neg to the paper in a very direct way. I keyed my PMK and pyrocat negs to my paper. I did Sandy's EPC process to key the negs from the different developers to the end - the paper, which for me is a vc paper as many other people use. To create the 'perfect' negative in a vacuum is silly unless that is the end result.

If you are consistent and methodical in your approach then my system works very well. Ikey everytihing to a vc paper w/o a filter which is very close to using a #2 filter. This way I can go down to filters 1.5, 1 and less or up to 5 if necessary. On the other hand if I just averaged the development of my negs from 4.5 munites to 6.5 minutes and through them into a rotary processor for just over 5 minutes then I might need a more flexible system because my negs were not processed appropriately.

It just depends on how systematic you are when photographing. I prefer careful testing and exposure of my film and then careful testing for my normal and plus and minus times. I then use the information gathered while I tested. I don't through it away and just slam things through a rotary processor. This is where the craft comes into play on a daily basis. Otherwise such rigid testing is just an academic exercise to beat people with.

steve simmons

[Jorge Gasteazoro]

what is the tonal distribution?

what is the reproduction cycle?

Perhaps I should ask a biologist about the second one. These are not photographic terms. Where did you get these terms?



I rest my case.......

Really sad, not only are you unaware of your ignorace, but you choose to flaunt it for all of us to see......

Perhaps you might want to consult "Controls in Black & White" by Dr. J. Henry. Or Todd and Zakia's Sensitometry so you can learn where I "got" these terms and how they are applied. Is it any wonder when someone sends you a technical paper you do not understand it? Some "Journal" you publish....