SLIMTs; possible small research project

davidkachel · Oct 21, 2008

Well, either someone will look into this or they will not. In either case, the passing of the baton as it were, has been attempted.

As someone who has made considerable use of a densitometer and can perhaps lay some minimal claim to knowing what he is talking about, supported by past achievement, may I suggest that some of you consider the possibility that a densitometer can be and most often is, far more of a detriment than a help to the practice of photography.

Sensitometry, contrary to the opinions of far too many, is NOT directly applicable to the exercise of practical photography and attempts to force it to be otherwise only result in poor photographs.

At least now I have a pretty good idea where the legions of Phil Davis' BTZS pseudo-scientists came to rest.

Photo Engineer · Oct 21, 2008

A good densitometer and a good sensitometer are the key to turning pseudo-science into science.

Although it is well known at Kodak that "we sell pictures, not sensitometric strips", a good step wedge is needed to prove a point and see where one has been and to show one the direction to move in.

I doubt that visual inspection of a print from the above curves would give you an idea of what was wrong, only that something was "not quite right".

PE

Kirk Keyes · Oct 21, 2008

davidkachel said:
At least now I have a pretty good idea where the legions of Phil Davis' BTZS pseudo-scientists came to rest.

That is funny!

gainer · Oct 21, 2008

So a true scientist does not own or use a densitometer or its cousin the exposure meter, but manages to write scientific journal articles about ...what? I learned about the scientific method at NACA-NASA where I started as an Aeronautical Research Scientist and retired as "an internationally known expert in non-linear mathematical models of the human operator." I quoted from my last job description. Along the way I designed and did the math for star charts to be used by the Mercury Astronauts as backup guidance during reentry. I designed the star projector for an in-house built planetarium. I designed apparatus for observing the time history of pilot's lookpoint during real and simulated flight without touching the pilot. I think you will find the same technology in autofocus cameras designed afterward. I was the chief photographer on a series of fatigue tests performed at Langley Research Center because I could design and use an attachment for a 35 mm camera that allowed me to take clearer photos of suspected fatigue cracks in bolt holes than the Photographic Division could get with their 8x10 view cameras.

The scientific method starts with what amounts to a theory which is to be tested. The tests must be devised to show if the theory is wrong. If it is not shown to be wrong, another series of tests is devised, again with the objective of disproving the theory. If the theory is proved to be wrong, the theory is revised to include the new knowledge. The upshot of the whole operation can never prove that the theory is right, but at best that the theory is not wrong. The one theory that can be proved is the Incompleteness Theorem of Kurt Godel ( the O should have the umlaut). Briefly, any set of axioms is either incomplete or self contradictory.

So, if I am a "pseudo scientist" then so was Einstein, and a long list of others, including that Englishman who gave us gravity and co-invented the Calculus. Goodbye.

davidkachel · Oct 21, 2008

gainer said:
So a true scientist does not own or use a densitometer...

You seem to have a strong propensity to misread or misunderstand my posts.
No, a TRUE photo scientist does indeed own a densitometer.

The problem lies with photographers who fancy themselves scientists but who nonetheless, starting with unfounded assumptions, draw meaningless conclusions based on data collected under less than ideal circumstances then baselessly infer meaning for an at best, loosely related system.

In other words, my position is that a camera and a densitometer do not a scientist make and that many, many photographers have led themselves down the garden path believing they do. Some of the worst photographs I've ever seen were ones which had the DR of the negative perfectly matched to the exposure scale of the paper, just what many of the true believers would give their lives to defend. Densitometers do not for the most part, belong in a photographer's toolkit.

Now if you as an apparently well-established and credentialed scientist believe I was impugning your credentials by telling photographers they are not scientists and should not be playing at science, I don't quite know what to say.

However I will say this. Being a qualified scientist in any field does not make one a photographer. Even working at Kodak in the manufacture of film does not make one a photographer. Only being a photographer makes one a photographer. And a scientist trained in one field but working in a creative field for which he was NOT trained is just as prone to error and incorrect assumption as anyone else. Being a brain surgeon does not qualify one to be an architect, regardless of the size of the ego perceived to be threatened.

tim_bessell · Oct 21, 2008

I hope the mod locks this thread if it doesn't turn into an intelligent discussion with useful content. We all have opinion and personal views and that's fine, but let us stick to Mr. Kachel's original topic, please.

Kurt Gödel -- an umlaut on my computer anyhow, i think.

Photo Engineer · Oct 21, 2008

David;

I have been both a published Kodak photographic engineer and a prizewinning and published professional photographer. I think I can speak from both standpoints then. Wouldn't you agree?

I've been in the photographic industry and profession for nearly 50 years.

PE

davidkachel · Oct 21, 2008

tim_bessell said:
...but let us stick to Mr. Kachel's original topic, please.

I agree. I didn't expect to have to defend myself by making what I thought would be received as a generous gesture.

I will respond to no further posts.

If someone is interested in pursuing the research I suggested and needs to communicate with me in that regard, please send me an email. I will not respond to anything else.

I had forgotten what it is like to deal with photography's religious right.

Mark Layne · Oct 21, 2008

davidkachel said:
If you are experienced with Selective Latent Image Manipulation Techniques and are interested in doing a small research project, here are the details...

In going through my now well-yellowed notes from my original SLIMT research I noticed one area I had intended to look into and never did. As I no longer have a conventional darkroom I will not be pursuing this myself. (For those who don't know, I am the inventor of all SLIMT techniques and a few others.) This is a relatively promising area and should be easy to investigate.

It has to do with two basic fundamentals of the behavior of photographic materials:

1. Developers and photographic materials have what are called "induction times". For example, the length of time that elapses between immersing film into developer and the moment the first silver halide crystal develops is the induction time for that developer/film combination. Development does not begin instantly. Also, and very important, the more exposure a silver halide crystal has received, the shorter the induction time for that individual crystal. This is the reason highlights begin development long before shadows and is also the reason that as you reduce development time to compensate for a subject with a long reflectance range you also lose film speed: lesser exposed areas dont develop at all because they don't reach their induction times before development is halted.

2. Developers are not the only photographic solutions that have induction times. Fixers and other chemicals do also. This is the reason monobaths (developer and fixer in the same solution) can work. If correctly formulated the induction time for the developer in a monobath is much shorter than that for the fixer and therefore development is complete before the fixer can begin to work.

Potassium ferricyanide, the bleach used in most SLIMTs, also has an induction time. In addition, most all film developers contain potassium bromide, the other essential ingredient for SLIMTs for film (SLIMTs for paper do not need it). Therefore, adding potassium ferricyanide directly to film developer has the potential, if the formula is correctly balanced, of performing both the latent image bleaching AND film development at one and the same time.

This single bath process would have the likely benefit of being more predictable and consistent. It would also likely provide inherently more even development (the single bath concept, like conventional monobaths, tends naturally toward more even development). SLIMTs are already consistent and predictable and development also is even, but more is always better. Conventional SLIMT concentrations are so minute that small errors in formulation can potentially produce noticeable errors in final density range. This potential should be reduced by a single bath as induction time for the developer would tend to play a significant role in stopping bleaching.

If doing this myself I would start with a weakened developer (probably about 50% of normal strength) and a stout (far higher than normal SLIMTs) potassium ferricyanide concentration, two identically exposed negatives, one developed identically in the same developer but without bleach. This would be a 'proof of concept' test. The point is to see if it is possible for the bleach to have a shorter induction time than the developer. If the negative developed with bleach in the developer shows any tendency to be usefully flatter, or even if it is blank, this would largely prove the technique is viable and only needs to be refined.

There it is. I have been sitting on this potentially useful SLIMT for about a decade. If you are interested, feel free to take off and run with it. If you can make it work, write an article, teach workshops, sell it to Microsoft for a million dollars... well, maybe not that last one. Just be kind enough to give credit where credit is due. And please apprise me of your results.

David Kachel

Not keeping a darkroom seems to me to be like abandoning a Ferrari for a Fiat
Mark

MurrayMinchin · Oct 21, 2008

Over 20,100 of us are actually kinda nice, and not too confrontational

Murray

monkeykoder · Oct 21, 2008

And most of the rest have good points but are just a tad on the caustic side.

Vaughn · Oct 21, 2008

monkeykoder said:
And most of the rest have good points but are just a tad on the caustic side.

Especially when confronting an equally large ego...

Vaughn

Photo Engineer · Oct 21, 2008

davidkachel said:
However I will say this. Being a qualified scientist in any field does not make one a photographer. Even working at Kodak in the manufacture of film does not make one a photographer. Only being a photographer makes one a photographer. And a scientist trained in one field but working in a creative field for which he was NOT trained is just as prone to error and incorrect assumption as anyone else.

Well, I found this statement interesting, thus my response. And, it was made even though I was agreeing with David, just adding more information from my experience.

PE

dancqu · Oct 21, 2008

davidkachel said:
Well, either someone will look into this or they
will not. In either case, the passing of the baton
as it were, has been attempted.

I'll check it out. I've slowly over the years collected
a large number of 120 negatives but done very little
printing. Mine has been a somewhat casual approach
to exposure and development. Overall when printed
the collection will be needing local and global
contrast correction.

I've been bothered by the enormous dilutions
required of the method as originally formulated.
My scale's resolution is 0.01 gram but I weigh no
less than 1.0 gram. As I use print developer very
dilute one-shot, repeatability may easy. Dan

Kirk Keyes · Oct 22, 2008

gainer said:
I learned about the scientific method at NACA-NASA where I started as an Aeronautical Research Scientist and retired as "an internationally known expert in non-linear mathematical models of the human operator."

Pat - I can't believe this!?! I always figured you leaned about the scientific method in college.

Kirk Keyes · Oct 22, 2008

davidkachel said:
No, a TRUE photo scientist does indeed own a densitometer.

The problem lies with photographers who fancy themselves scientists but who nonetheless, starting with unfounded assumptions, draw meaningless conclusions based on data collected under less than ideal circumstances then baselessly infer meaning for an at best, loosely related system.

Not only that, they need to inderstand how a densitometer works, and to have a well-calibrated densitometer, to boot.

As to your second paragraph, welcome to APUG and the rest of the interweb.

Actually David, I'm glad to see you here. I too enjoyed your writings in Photo Techniques.

luxikon · Oct 22, 2008

Thanks for the link to your site, David. It's a treasury for me.

gainer · Oct 22, 2008

Kirk Keyes said:
Pat - I can't believe this!?! I always figured you leaned about the scientific method in college.

Not much. What we were taught was facts and math. I never had to write a report describing the thesis of an experimental plan, the plan itself, the results of the experiments and an analysis of the results until I worked at NACA. All this time I did practise photography as a hobby. I rode my hobby horse enough to build an enlarger using pipe fittings, a lens from elements purchased from what was then Edmund Salvage Company, a home made iris and a home made bellows.

Being a scientist does not keep one from being a photographer. I think being a scientist can help me and others be better photographers as a result of our urgent need to measure things in order to explain their behavior. I think you will agree, and we know for a fact that PE does. In point of fact, any photographer who tries something different because of an idea that it might have a particular effect on a photograph is a scientist. There is a thesis (idea), a plan for testing it, and a report of the results (picture). Generally, the thesis involves some chemical or physical change in the processing. As such, if it is to produce a visible change in the photo it will produce a measurable change as well. The photo of a step tablet is no less valuable than a photo of the Grand Canyon as a test of the proposed method, and changes in its image are much easier to measure. Furthermore, one practiced in the art can more easily predict the effects of the change in process on a photo of any other scene by analyzing its effect on the step tablet image. That is my feeling on the subject at hand and the reason I strongly object to being labelled (or should it be libelled) as a "pseudo-scientist"

Kirk Keyes · Oct 22, 2008

gainer said:
I think you will agree, and we know for a fact that PE does. In point of fact, any photographer who tries something different because of an idea that it might have a particular effect on a photograph is a scientist. There is a thesis (idea), a plan for testing it, and a report of the results (picture). Generally, the thesis involves some chemical or physical change in the processing.

Well, Pat, I certainly agree you do not fall into the definition of a pseudo-scientist.

But I think a lot of people that are not well versed in science, and even then some that are, end up making a flawed thesis, devise a poor plan for testing it, and/or they misinterpret the results. Even when you are skilled in the field, it still sometimes happens. Experiment design is not as easy as it seems sometimes.

So while it's easy for someone to be a scientist, it's sometimes not so easy to be a good scientist. Especially when working outside of one's field of expertise.

And not that that's an impossible thing to do, but it does take a lot of self-education to pull it off well. I know I feel that way after reading lots of book on emulsion making, when my background is analytical chemistry. But an advantage I have over many, is that I do have a background in basic chemistry. But I know I have a long way to go to just scratch the surface of that subject.

gainer · Oct 23, 2008

How does one define his field of expertise? The curriculum at WVU for any branch of engineering was quite general for the first two years, and even if one changed after that, those credits that might be special to the original branch could usually be applied as electives. All engineers had to have completed 154 credit hours of courses, compared to 120 for Arts and Sciences. We had courses in welding, surveying, machine shop, drafting and other subjects that were then common to all branches of engineering. I don't know how it is these days, but that kind of education was quite applicable to employment at NACA. The engineering was considered primary at NACA, why not at school? At NACA there was seldom a report with a single author. There could be an aeronautical engineer, a mechanical engineer, an electrical engineer, a physicist, a psychologist, a mathematician, all on the same project. After a report was presented for publication it was reviewed by the branch head, the division chief, and if it passed it was subjected to peer review and sent to the other NACA Research Labaratories for review. I served as chairman of several Editorial Committees in my thirty years of service and as member of many more, as did most of my compadres. I can say from experience that the ratio of number of reports to number of hours studying was very low.

Lee L · Oct 23, 2008

gainer said:
We had courses in welding, surveying, machine shop, drafting and other subjects that were then common to all branches of engineering. I don't know how it is these days, but that kind of education was quite applicable to employment at NACA.

Talking with a friend a couple of years ago, an EE who hires recent college EE grads for beginning positions: in interviews he asks them to draw a simple power supply schematic by hand. He gets a high percentage who simply can't do it, either don't know components, standard designs, or can't generate a schematic on that level without a CADD package on a computer that has pre-drawn components to insert. It's definitely not the old days.

Lee (not an engineer of any kind)

gainer · Oct 23, 2008

A professional musician friend once told me:"Those who can, do. Those who can't, teach." He was young and able then. He may have change his tune a little now that he is old.

I believe I told this once here, but maybe there's a new batch of readers. We had a M.A in math come to work. He was like that EE. He went to take the oral exam for the doctorate and came back obviously shaken. He said "My gosh...They asked questions about arithmetic!"

Raghu Kuvempunagar · Nov 1, 2021

Photo Engineer said:
Because the dense negative areas (highlights) have the slowest grains (finest) and all of the coarse grains are totally exposed, the amount of latent image present there is greatest

..

Since fine grains in this region present a greater surface area per unit mass, they tend to bleach faster than the mid and low scale image. They also bleach faster because the finer grains (slower component) tends to contain less iodide which acts as a bleach inhibitor on coarser grains.

As a result the images produced by this process generally tend to lose highlight detail and go up in grain if you go too far outside of this field.

..

You will have to experiment with each type of film you use, because the latent image, grain size, iodide content and etc. will vary from film to film. You will have to optimize it for your particular film and desired effect.

Best technical explanation of SLIMT that I could find.

SLIMTs; possible small research project

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