SLIMTs; possible small research project

[davidkachel]

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 don’t 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

 

[MurrayMinchin]

While what you're proposing sounds intriguing, your original SLIMT method is such an improvement over previous techniques for reducing contrast in negatives that I don't know how many takers you'll have to test this new idea. There is fertile ground here on APUG though, so you may just spark somebody into action.

I'd like to thank you, David, for connecting the historical and inspirational dots to come up with the SLIMT method of reducing contrast in negatives in the first place. SLIMT has allowed me to walk away with usable negatives from difficult circumstances, and for that, I thank you!!!!!!!!!!

Murray

 

[Mick Fagan]

David, are you the David Kachel from Photo Techniques early years?

If you are, you wrote some very interesting articles, which I enjoyed a lot.

I do believe a like system (as you have described) was used by DuPont in the graphic arts field starting in the fifties. At least in Australia for speed and ease of use in manufacturing (developing) film which would be used for half tone conversion use in newspaper printing, in the next processing step.

I had some quite interesting conversations with operators of our etching and film developing processes when they were near retirement in the late seventies. Their stories of photographers films coming out looking fantastic, then not so great the next time, with a technique that seems remarkably similar to yours.

Mick.

 

[luxikon]

Sounds very interesting. I searched the web but did not find precise description of SLIMT (quantities of chemicals needed, times of presoak, temperature ...). Where can I find detailed information about this technique?

luxikon

 

[davidkachel]

While what you're proposing sounds intriguing, your original SLIMT method is such an improvement over previous techniques for reducing contrast in negatives that I don't know how many takers you'll have to test this new idea. There is fertile ground here on APUG though, so you may just spark somebody into action.

I'd like to thank you, David, for connecting the historical and inspirational dots to come up with the SLIMT method of reducing contrast in negatives in the first place. SLIMT has allowed me to walk away with usable negatives from difficult circumstances, and for that, I thank you!!!!!!!!!!

Murray

Well you'd be surprised how few people adopted SLIMTs in the first place, at least as reported by my very empty mailbox. As simple as it is, it was still too much for most people. Hence the mono-bath idea.

You are most welcome. I'm glad you've found the technique useful.

 

[davidkachel]

David, are you the David Kachel from Photo Techniques early years?

If you are, you wrote some very interesting articles, which I enjoyed a lot.

I do believe a like system (as you have described) was used by DuPont in the graphic arts field starting in the fifties. At least in Australia for speed and ease of use in manufacturing (developing) film which would be used for half tone conversion use in newspaper printing, in the next processing step.

I had some quite interesting conversations with operators of our etching and film developing processes when they were near retirement in the late seventies. Their stories of photographers films coming out looking fantastic, then not so great the next time, with a technique that seems remarkably similar to yours.

Mick.

Yes, that would be me. I'm glad you enjoyed the articles.

When doing the original work for SLIMT I researched the literature going back over a hundred years and found only two references of import, neither of which involved DuPont. I would be interested in seeing what they published. Aside from the Sterry method which involved only photographic paper and horrible speed losses, latent image bleaching was used only for testing experimental emulsions... as far as I know. It would be interesting to discover DuPont had a use for it in half tones.

If photographers had mixed results they may have followed the path pioneered by Sterry which was of course largely a dead end.

 

[davidkachel]

Sounds very interesting. I searched the web but did not find precise description of SLIMT (quantities of chemicals needed, times of presoak, temperature ...). Where can I find detailed information about this technique?

luxikon

I have a rather anemic web site I recently started but have had to ignore while paying attention to the more pressing problem of getting up to speed with digital photography. There I have posted some of the more significant of my original articles from D&CCT.

http://www.davidkachel.com/history.html

You will find the original article announcing SLIMTs "Zone System Contraction Part III — SLIMT's". You may also find some uncorrected spelling errors and perhaps missing illustrations in some of the articles. But for the most part the meat of all my techniques is on the web site.

 

[eclarke]

While what you're proposing sounds intriguing, your original SLIMT method is such an improvement over previous techniques for reducing contrast in negatives that I don't know how many takers you'll have to test this new idea. There is fertile ground here on APUG though, so you may just spark somebody into action.

I'd like to thank you, David, for connecting the historical and inspirational dots to come up with the SLIMT method of reducing contrast in negatives in the first place. SLIMT has allowed me to walk away with usable negatives from difficult circumstances, and for that, I thank you!!!!!!!!!!

Murray

I second Murray, I use this with reckless abandon now and have found that it really works in my Jobo. Step 1, bleach an appropriate time (with my dilution, it's about 1 stop of highlight for 1 minute of bleaching) Step 2, rinse 1 minute, Step 3, pretend it's a normal neg and develop as usual. I have also been doing it with paper and it's equally powerful there. I will try this combo this weekend, I always expose 2 sheets for a given photograph and have lot's of good test subjects...Evan Clarke

 

[eclarke]

I mean lots...DUH..EC

 

[Photo Engineer]

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 and therefore the appearance of the image is related to the number of sites as well as induction period. This gives us a qualitative weighting of development rate that is not exactly related to induction period.

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.

We did a lot of work on this type of process during work on catalytic processing. There are limits beyond which you will not wish to pass if you want to get good images. 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.

This will indeed be a research project. IDK how small it will be.....

PE

 

[gainer]

If it is to be done properly, it will be an extensive set of experiments. It will not be sufficient merely to point out the good points of SLIMT. Comparisons must be made with other methods that purport to produce similar results, the final print being the objective measure. My only experience with SLIMT was in printing. Given an existing negative of greater than normal contrast or worse yet two areas each of normal contrast but different densities, there will be several ways to print it including dodging-burning, unsharp masking, flashing and SLIMT.

I have a small diffuse light source controllabl by an iris that I can fasten to the side of my enlarger. I have an easel densitometer that can be calibrated to read Zones. With the flashing lamp off, I set the enlarger diaphram to read, say, Zone 3 in the significant shadow. I turn the flasher on and set its diaphram to read, say, 9 in the highlight. The reading in Zone 3 has not changed because of the logarithmic scale of the densitometer. The exposure is made with both lamps on, of course. I don't remember much about the ferricyanide solution except that I followed the instructions in the magazine. The results of the two methods were not enough different to warrant finding room for another tray. The easel Zone meter was also useful in the case of a photo of a window when dodging was needed.

My method is not applicable to controlling contrast of the original negative. The other well known David, Vestal, wrote about preflashing negatives, which he learned from his mentor.

Flashing, pre- or post-, and SLIMT change the shape of the characteristic curve they are used on. Whoever undertakes the suggested research must be prepared to show the differences.

Another possibility not to be overlooked is that of using both SLIMT on the negative and unsharp masking on the print for those difficult window scenes.

I think not just a research paper, but a book could come out of this research.

 

[ic-racer]

Thanks for the links to the articles.

Looks like your technique adds a hump to the middle of the curve. I would think you are "robbing Peter to pay Paul" with a loss of contrast in some areas and a gain in others. As always, the proof will be in the prints!

I have recently been working with a very contrasty film (unmarked, but similar to Tech pan or Copex) and actually was trying to avoid this hump. So maybe the hump is not such a bad thing. I'll keep your papers in mind as I am working on it. The posted JPEG shows the same film with two different processing strategies. I tried a lot of things to lower the contrast of that film an reduce the hump, which I finally accomplished. So it is very interesting to read your papers which suggest that this hump can be a good thing.

A constructive note, when you define 'contrast' in that first paper I think, as a style point, you shouldn't accuse people of using the word contrast wrong. I would just define how you are going to use the word contrast in your paper and move on. If I were to make a suggestion, I would define 3 or 4 contrasts, for example the english dictionary implies that a scene with a high SBR DOES have a lot of contrast (dictionary definition: "5. The difference in brightness between the light and dark areas of a picture, such as a photograph or video image.") So I would call that one "OVERALL CONTRAST." The the difference from one zone to the next could be something like INTERZONAL CONTRAST, MICRO CONTRAST, or LOCAL CONTRAST. Then there is the slope on the H&D curve which could be just plain "CONTRAST" and then there can be a line tangent to any point on the HD curve which could be called INSTANTANEOUS CONTRAST. And also there is CONTRAST INDEX which you measure with that clear template.

 

[davidkachel]

If it is to be done properly, it will be an extensive set of experiments. It will not be sufficient merely to point out the good points of SLIMT. Comparisons must be made with other methods that purport to produce similar results, the final print being the objective measure. My only experience with SLIMT was in printing. Given an existing negative of greater than normal contrast or worse yet two areas each of normal contrast but different densities, there will be several ways to print it including dodging-burning, unsharp masking, flashing and SLIMT.

I have a small diffuse light source controllabl by an iris that I can fasten to the side of my enlarger. I have an easel densitometer that can be calibrated to read Zones. With the flashing lamp off, I set the enlarger diaphram to read, say, Zone 3 in the significant shadow. I turn the flasher on and set its diaphram to read, say, 9 in the highlight. The reading in Zone 3 has not changed because of the logarithmic scale of the densitometer. The exposure is made with both lamps on, of course. I don't remember much about the ferricyanide solution except that I followed the instructions in the magazine. The results of the two methods were not enough different to warrant finding room for another tray. The easel Zone meter was also useful in the case of a photo of a window when dodging was needed.

My method is not applicable to controlling contrast of the original negative. The other well known David, Vestal, wrote about preflashing negatives, which he learned from his mentor.

Flashing, pre- or post-, and SLIMT change the shape of the characteristic curve they are used on. Whoever undertakes the suggested research must be prepared to show the differences.

Another possibility not to be overlooked is that of using both SLIMT on the negative and unsharp masking on the print for those difficult window scenes.

I think not just a research paper, but a book could come out of this research.

If I understand you correctly, you are comparing flashing and similar techniques to SLIMT with regard to papers. This comparison is invalid as flashing is intended to affect the less dense areas of a print while SLIMTs affect only the denser areas. To my knowledge there is no traditional technique that compares even remotely to the behavior of SLIMT with photographic paper; other than, of course, the old Sterry method which is vastly less effective. SLIMT with paper can be used to achieve grade 0 shadows on a grade 4 or five paper while maintaining grade 3 or 4 highlights (rough approximation; every paper is different).

Also, the research suggestion I made was with reference only to negative processing. The single bath approach to SLIMT, for obvious reasons, is not applicable to print development.

 

[davidkachel]

Thanks for the links to the articles.

Looks like your technique adds a hump to the middle of the curve. I would think you are "robbing Peter to pay Paul" with a loss of contrast in some areas and a gain in others. As always, the proof will be in the prints!

Don't know where you got this idea or the characteristic curve you posted. This certainly did not come from my research or anything I published. Nor has any SLIMT user ever reported anything along these lines.

In fact, there has been enough SLIMT use over enough years that it is reasonable to conclude there are no known drawbacks whatsoever to SLIMTs. At least none has ever been reported to me and SLIMTs have been taught in several universities, are/were used by at least three commercial labs I know of and one young lady in Georgia even wrote her master's thesis on SLIMT (though I lost contact with her and never got a copy so don't know if she actually completed it).

I am simply suggesting that someone might wish to pick up the ball so to speak and look into a new variation of an already proven technique. If you are interested in disputing the efficacy of SLIMT, I think you arrived about 18 years too late.

 

[gainer]

So you don't really need the research. You already know how it will come out.:confused:

 

[Photo Engineer]

IC;

The hump in the curves above is typical of a 3 component blend done improperly or a film used in a developer for which it is not designed.

You can just about see the 3 components separating out in the curves.

PE

 

[davidkachel]

So you don't really need the research. You already know how it will come out.:confused:

????????????

Don't know what I could have said to make you think I already know how it will turn out. I have a strong suspicion it will work, but can't know until someone actually does it.

As for my own use, I have no interest. I am completely out of analog photography except for scanning pre-existing negatives and therefore have no motive whatsoever in posting the original information/suggestion other than to pass it on to those who might make use of it and benefit from it. It is a gift if anyone wants it. I just didn't think it would be right to take it to the grave with me.

I was talking about someone continuing the research on apples. You responded by saying you had results you didn't like with oranges because said results were so similar to that which you achieved with watermelons.

Plainly you have no interest in doing the research and I have no interest in arguing the efficacy of an established and highly effective group of techniques I invented nearly twenty years ago.

 

[ic-racer]

Don't know where you got this idea or the characteristic curve you posted. This certainly did not come from my research or anything I published. Nor has any SLIMT user ever reported anything along these lines.

Those curves were mine. This one is yours. I think they both have a 'hump' in the middle.

 

[JOSarff]

David, great to hear from you.

The curve IC-RACER posted look in no way like curves from my SLIM negatives or tests. I've been using David's techniques very successfully with film and prints since they were published in the early 90's.

Joe

 

[Photo Engineer]

IC;

In the figure above, this again shows either a bad film with separation of the 3 components of the emulsion, or a poor process, ie. one the film cannot cope with.

Either way, the results will not yield a good print with a curve like that. There is little discrimination (low contrast) in the mid tones and so depending on where the image was, you would have to use 3 grades of paper or split printing at perhaps grades 4, 2 and 0 to give a good print. I used the extreme grades just as an example. Actually 2 grades might suffice, but they would require 3 printings for the 3 ranges shown.

I would never coat such an emulsion blend, if it is the coating. I would never use such a film, if that is what you get from batch to batch in a standard process such as D-76.

PE

 

[ic-racer]

IC;

The hump in the curves above is typical of a 3 component blend done improperly or a film used in a developer for which it is not designed.

You can just about see the 3 components separating out in the curves.

PE

Thanks PE. I was preparing those graphs to post to get your (and other's) opinions, but wound up getting a good curve after all. BTW the film is unmarked cinefourography film used for making movies of a fluorescent image intensifying screen.

 

[davidkachel]

Those curves were mine. This one is yours. I think they both have a 'hump' in the middle.

Yes, that is my illustration... taken from a different article on a different technique I invented, NOT from the SLIMTs article.

I believe I already said this to another poster but, if you are not interested in doing the suggested research, why are you posting? To argue with me about a technique that is already proven over a span of nearly two decades? If you believe SLIMT has nothing to offer then don't use it. If you expect you are going to convince me I was wrong about SLIMTs, good luck. The amount of evidence to the contrary is massive, AND I don't care. I didn't come here for an argument, just to pass along something potentially useful.

 

[Photo Engineer]

I will second that. SLIMT is useful. I feel though that it is something that must be researched for each film/process combination and as the original premise stated is the subject of a research project in itself for the person who wants to use it.

The self limitations of the possible results due to the nature of the process also limit what you will ultimately be able to obtain.

PE

 

[ic-racer]

If you believe SLIMT has nothing to offer then don't use it.

On the contrary. I was excited to see that one of the uses for SLIMT you cited was "high contrast film" which is exactly what I was working on last week. I guess I was mislead by the caption on your graph indicating "IDEAL." The bleached curve (figure 1 in Part III) I could not tell if you did not extend it far enough to see the hump. If you tell me the bleach does not make a hump, thats great, I will want to try this with my film and compare it to what I have already come up with.

 

[davidkachel]

On the contrary. I was excited to see that one of the uses for SLIMT you cited was "high contrast film" which is exactly what I was working on last week. I guess I was mislead by the caption on your graph indicating "IDEAL." The bleached curve (figure 1 in Part III) I could not tell if you did not extend it far enough to see the hump. If you tell me the bleach does not make a hump, thats great, I will want to try this with my film and compare it to what I have already come up with.

Be VERY careful with HC film and use test rolls/sheets, not important film first. My tests with Kodak's Tech Pan were very successful from the standpoint of contrast and speed retention but I was not able to get development I considered sufficiently even to be acceptable. Others have had success I understand.

Try using TWO presoaks. The first, only water and one drop of surfactant. The second, water and SLIMT bleach. Try drastically different agitation schemes and use plastic not stainless tanks if processing roll film.