SLIMT and Why You Should Be Using It

[clayne]

I don't know if this thread is providing any more info than the last one.

What I would like to see is a thread or article comparing, for example, printing SLIMT, Selectrol Developer (or clone), and Multigrade paper, in terms of expense, ease of use, repeatability, availability of supplies and range/shape of curves.

ic-racer: I'd love to see a pot of gold with a beautiful woman handing it to me as I exit my door each morning for work - however, not gonna happen. The beauty of an open forum like this is that if you'd like to see different examples of how something works you have the power to do that and the power to provide your own findings back into the thread - complete with scanned prints as I did.

I'm not going to go and burn a box of paper because you can't be bothered.

Now in reference to the other thread - it was particularly on concepts of combined baths, etc. You went at it with your densiometer, other people got involved, and it nose-dived quickly. I feel this thread actually allows us to reexamine the overall concept of SLIMT again - as it's being ignored by the majority of darkroom printers is a plain shame.

Can you show us an example where the high tones on the SLIMTified print match the high tones on the print done with a standard process? Every SLIMT example so far has been much lighter overall, not just in the darker areas. It would also be good to have examples with standard printing manipulations applied (changes in contrast filter or grade of paper, changes in developer, burning and dodging, etc.)

Please see paragraph above to ic-racer. I'm not going to burn a box of graded paper just to "prove" something to you guys, honestly. Because at this point you and a few others have already approached this thread as critics - disclaiming it's usefulness.

The example I gave you is a straight print on #4 with Selectol 1+2. Since I have the neg still in the carrier I may be able to do you a #2 print with no other local modifications to show a "sane" baseline. I don't have #1 paper.

The point is, if you are going to tell us all that we "should be" doing something, then really let us know why. As far as I can see from the examples posted, you get a lower contrast print, but also a much lighter print over all.

You should know that exposure can easily control this. I chose that print as the one I liked best because I was fine with a rather "bright" print that could convey the overall group as best as it could. I didn't have a #2 comparison print at the time to choose against. In short you should expect less contrasty highs and less contrasty shadows, overall flatness, and still no way to fit it all in without heavy local work (which is more than SLIMT work).

The one picture that would best illustrate the technique is not shown, so how can you expect anything but a lukewarm reception at best? This is the aforementioned picture in which the high tones on the standard-processed print and the high tones on the SLIMTified print match.

I think you're arguing this in a perverse way. I'm giving you a pathological combination of scene, negative, and paper - to show that with that BAD combination of materials - SLIMT is able to pull out quite a usable print. What is not understood there? If anything that's telling you that in a relatively "bad cases" this method is fairly easily able to get you something workable.

If you're going to tell me that printing it on MG, jumping through the acrobatic hoops of split-grade printing, dodging/burning/etc. is EASIER than immersing a piece of paper in a bleach bath for 1 minute and developing as normal, then I don't know what to tell you.

 

[ic-racer]

ic-racer: I'd love to see a pot of gold with a beautiful woman handing it to me as I exit my door each morning for work -

I actually DO have that, but I married well....


Seriously, I'd contribute the "Multigrade" printing info. As far as the SLIMT info, are you saying you don't have any paper curves to post?

Are you also implying that, although you use the system, you don't know how hard it is to do, or you don't know how much the chemicals cost, or you don't know how hard it is to get the chemicals?? I think you know all that stuff. Don't keep it a secret. We just need enough info to make an informative table. I'll bet you can come up with the info off the top of your head.

In terms of the paper curve, if you don't have any, then you don't need to waste a box of paper, just some strips from a single sheet. Probably only need 5. If you don't have a reflection densitometer to read them, put the strips in an envelope and send it to one of us to read.

If you don't have a stepwedge, I'd donate 5 strips of step-wedge-exposed paper for you to process but I only have MG paper

 

[davidkachel]

Do you have any way to lead us to the exact articles of which you speak?

The first SLIMT announcement appeared in the Sep/Oct 1990 issue of D&CCT. (Damn I'm old!)

The fellow who invented the contrast increasing technique for RA-4 paper published it either in the same issue or the one before it. Then, either in the same issue as SLIMT, or the one after it, at my request he published his findings on SLIMT with color paper. I had no color equipment and since I knew about his technique, I felt he was the ideal person to do the testing for me. I asked if he was willing and he agreed. So, both techniques are published under his name, though one is his and the other mine. As I recall, his technique causes a slight shift toward magenta, easily compensated because there is no divergence of curves and SLIMT causes no color change. BUT, it's been 20 years so I disavow any responsibility for my memory.

Both techniques were extensively tested by the best color people in the world at the time, so if you have any problems, stick with it. They both work, absolutely.

As for "fuggem". No, if he doesn't publish, he doesn't lose anything. I have been published on four continents in numerous languages in a dozen periodicals over 70 times. What I got for that is that a few of you recognize my name (and some consider me a target).

There is no money involved that doesn't make paper hat wages look EXTREMELY attractive. There is no ticker tape parade. There is no applause and there are no prizes. Mostly there is just deafening silence, occasionally shattered by someone who either did not read your article at all, or read it and entirely failed to grasp it. And then there are those who are so jealous and desperate for attention they feel they have to discredit you at any cost. I have never told anyone this before, but a former, now deceased, contributing editor to D&CCT actually threatened the editor with resignation if the magazine published one of my articles because it exposed (not by name but by empirical proof) some of his ideas as foolish. The editor did not bend, the article was published and the person in question did not resign. In short, there is a lot of grief and very little incentive indeed and my original point was that a lot of very valuable information is never made available to the photographic community precisely because of the kind of behavior exhibited in this thread. You can say that people should have thicker skins all you like, but the loser IS and always will be the photographic community. The secret keepers lose nothing. They already possess the valuable information. People who do research have always been by nature, somewhat reclusive and thin-skinned. Saying they should be otherwise gets you nothing and is short-sighted. Then the only people who might share what they know with you are those few like me who have teeth and enjoy the taste of blood! ;-)

 

[ic-racer]

Ok here is my contribution...

MULTIGRADE vs SLIMT COMPARISON:

MULTIGRADE PRINTING:
Cost: MG paper cost about same as graded paper. Dichroic heads can be expensive and dependent on the power supply, but they can also be cheap and run off the mains. They all have fade-free filters. If printing with a non-dichroic had, acetate multigrade filters are about $50-60 a set.

Ease of use: with a calibrated table and a dichroic head, you can change grades in about one minute. If that is too complicated, you can make 2 exposures with maximum filtration and adjust contrast that way, as many do with the 'split grade' technique.

You can also apply different contrast to different parts of the image. Though in almost 40 years I have only done this a hand full of times, but I suspect there are experts at doing this out there.

Availability of supplies: I have never seen B&H or Freestyle out of multigrade paper. I have not read any 'doom and gloom' stories about the major manufacturers discontinuing multigrade paper. In fact, it may be the graded paper that is at risk.

Graded paper can be developed with many 'standard' paper developers.

Efficacy: Here is a family of paper curves representing the Ilford MG FB paper I use.

 

[ic-racer]

Now if we could have a contribution to the comparison by a Selectrol user and a SLIMT user...

 

[clayne]

Seriously, I'd contribute the "Multigrade" printing info. As far as the SLIMT info, are you saying you don't have any paper curves to post?

I highly encourage you to try it with MG papers and possibly any "difficult" or other negatives you might have on hand. Or go wild and crazy and try it with your best negatives.

Are you also implying that, although you use the system, you don't know how hard it is to do, or you don't know how much the chemicals cost, or you don't know how hard it is to get the chemicals?? I think you know all that stuff. Don't keep it a secret. We just need enough info to make an informative table. I'll bet you can come up with the info off the top of your head.

I put this all in the original post, though. I even linked to the exact chemical to buy from Freestyle, although most people already have pot-ferri. I stated the procedure I used and relied on inference of the reader to figure out how hard or easy it is. Mix a stock, done. Mix a working session stock from that, done. Dilute said working stock into a tray with a spoon, hammer, or electron microscope if preferred. Bleach for 1-2 minutes and develop. Adjust variables after processing - same exact thing as any other printing process: do something, adjust, repeat.

People might see a lot of steps and assume it's difficult. Some of those steps are relatively 1-time steps. It isn't difficult for anyone used to darkroom work.

In terms of the paper curve, if you don't have any, then you don't need to waste a box of paper, just some strips from a single sheet. Probably only need 5. If you don't have a reflection densitometer to read them, put the strips in an envelope and send it to one of us to read.

Why do you need any of this? I mean does one honestly need a densitometer to look at prints and compare by eye?

I'm not going to even attempt to figure out paper curves for the examples I've provided because a: I don't have the tools to do that, b: I feel it's not necessary to see the effect. Said effect being quite obvious because of the explicit choice of working with a very contrasty set of materials in the first place. If SLIMT gave me a print afterward that had the shadows only slightly lifted then it would of course not be as useful. That wasn't what the case was.

You're completely at liberty to try these techniques yourself - which was part of the impetus for the thread originally. Mixing a few pot-ferri bleach concentrations will take you 5 minutes.

Now if we could have a contribution to the comparison by a Selectrol user and a SLIMT user...

Your comparison was totally bunk. Those curves tell me nothing pertinent to this thread and neither do your non-existent real-world examples. Additionally you blanket ignore the known issues with contrast curves in VC paper anyways (but let's just not even get into that here in this thread).

Go back and read the original articles pointing out how one can control global shadow contrast independently of highlight contrast set by grade. How many times must it be beaten in here that in order to preserve the high contrast and printability of the highlights while at the same time preventing the shadows from becoming a swamp of black is *more work with VC techniques*. If you say "just use a lower grade" you're not reading.

You're also not going to change the fact that people successfully use this technique. The purpose of the thread was to try and draw constructive attention to it for which it deserves and possibly have a few others start using it. If it allows them to make more successful prints or explore creative options - then it's beneficial.

The continually interesting thing I'm noticing here in this thread (and others) is the apparent MO of a few people here to absolutely minimize the usefulness of things they don't use or "agree" with.

You know what else is weak here - and not entirely exclusive to this SLIMT thread? I post my images and photography. Most of the critics do not. That should tell you something.

 

[eddie]

It seems to me that any technique we can add to our arsenal is valuable. Whether it's the best, or easiest, matters less than the fact it exists. I, for one, appreciate the efforts made to further my knowledge, and understanding, of my chosen form of expression. There is more than one way to get to a desired result. What works best for some may not be best for others. Rather than being dismissive of the technique, allow for the fact that it may improve the work of other Apugers.

 

[davidkachel]

So, determined to compare toasters to television sets I see, despite my explanation. Either I am incapable of explaining it clearly, or some of you are simply not interested in listening. Mr. Layne is the only one who seems to have grasped it and you are all jumping on him. In either case, I see no point in beating this poor dead horse any further. You can continue to insist that you understand what you plainly have not read, or did not read carefully and I will go on my merry way.

 

[dancqu]

Theory of the Photographic Process - Mees & James - 1966

Someone with more photograph science might be able to chime
in, and in no way is it necessary for actually using SLIMT, but
exactly why does pot-ferri attack more densely exposed
silver when used pre-development, but reverse it's
behavior when used post-development?

David in his article Zone System Contraction Part III cites the
above mentioned reference. The exact mechanism involved is
not known. It is though reduced silver in the more exposed
areas that are affected. The phenomenon is known as
CONTRASTWISE bleaching. The little exposed
amorphous centers of reduced silver are
not so affected.

For further details Read Mees & James or enter David's
article title at Google. Dan

 

[clayne]

Or, if you prefer some other views, how about some old posts from rec.photo.darkroom, back in _1995_:

Newsgroups: rec.photo.darkroom
Path: swrinde!howland.reston.ans.net!news.cac.psu.edu!news.tc.cornell.edu!travelers.mail.cornell.edu!cornell!rochester!rocksanne!news
From: mcfar...@eso.mc (Doug McFarland)
Subject: SLIMTs - What is it ?
Message-ID: <1995Feb8.164619.16772@news.wrc.xerox.com>
Sender: n...@news.wrc.xerox.com
Reply-To: mcfar...@eso.mc
Organization: xerox.com
Date: Wed, 8 Feb 1995 16:46:19 GMT
Lines: 22

In a recent issue (jan/feb) of Darkroom & Creative Camera Techniques, a
reader responds to an article that David Kachel wrote about Selective
Latent Image Manipulation Technique(s). I gather from the response that
this process is bleaching a latent image (pre development ?) from B&W paper
with potassium ferricyanide to enhance highlight detail. I don't have
the original David Kachel article. Could some one explain this process
and give some starting points for experimentation ?

Thanks in advance -

--


Newsgroups: rec.photo.darkroom
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From: bg...@FreeNet.Carleton.CA (Michael Gudzinowicz)
Subject: Re: SLIMTs - What is it ?
Message-ID: <D3sxBE.2y8@freenet.carleton.ca>
Sender: bg...@freenet.carleton.ca (Michael Gudzinowicz)
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Date: Fri, 10 Feb 1995 20:38:02 GMT
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Doug,

The procedure is very simple... a negative with a large
density range is printed on a paper which is too contrasty to
print the image properly... for instance, printing a negative
meant for grade 0 on grade 5 paper. Before development, the
latent image is bleached to reduce its contrast to fit the
paper. On the paper, the high values have little density and
aren't affected much; the low values are reduced more. In
practice, one prints for the high values, and bleaches to
decrease the slope of the latent image density curve, so the
low values print properly. Usually, when printing on high
contrast paper, the high values are expanded; on lower
contrast grades, there is less of an effect; with very dilute
bleaches, fractional grade changes are possible.

The results complement print bleaching after development,
where negatives with insufficient range for the paper are
printed for low values, leaving high values over-exposed and
grey, which are then bleached. The high values are expanded
since they were separated by printing on the linear portion of
the paper's curve rather than the toe.

The results are paper dependent... I've used Ilfospeed,
Gallerie and Ilfobrom. Somewhere, Dave has a list which I'll
look up if he hasn't sent the info to you via e-mail.

The following is a note I sent to a friend who was didn't want
to use albumin POP to make prints of old wet plate negatives
for exhibition. If you intend to try the method, I'd recommend
running similar tests with a step tablet, different dilutions,
times, and paper grades, which will permit you to predict
results. The method works well to fit night shots with
extended ranges on G3 paper, without underdeveloping the
negative or using compensation which would compromise
separation.


Old note on SLIMT calibration:

I thought I'd share my calibration procedure for bleaching the
latent image of B&W printing paper, which permits one to print
negatives with density ranges in excess of 4.0 OD units,
without masking, the use of printing out paper or any real
inconvenience. During the past week, I contact printed a
number of old wet plate negatives, which ranged from flat 0.8
(G3) to > 4.6 OD, with most lying in the range of 2 to 4 OD
units. The prints with an excessive range, for instance, might
take 7 min to print highlight densities, while under identical
conditions a "normal" scale negative might take 3 sec. to
print on G1 paper. Due to the long exposures, I used a high
intensity source for contact prints; in areas of low negative
density, the paper would turn yellow as the latent image
"printed out".

The method I used was published by David Kachel and is a
modification of Sterry's method of bleaching the paper's
latent image before development to reduce its contrast. If I'm
not mistaken, Sterry's method which used dichromate was
published in David Vestal's "The Art of Black_and_White
Enlarging". Later Fyson & Levenson of EKC noted that
ferricyanide bleach would form silver grains proportional in
size to the bromide concentration, with concentrations of both
agents in the 2-10 g/l range giving finer grain than was
originally present restricted to the area where the silver was
developed.

After exposure, the latent image is bleached with a
proportional bleach (dilute ferricyanide/bromide) which
reduces the contrast of the yet undeveloped image evenly
across the entire tonal range. The print is then developed
normally (2 min Dektol or D-72, 1:1). Rather than proceed in a
hit or miss fashion, I tried the following tests to calibrate
the bleach concentration and time to the negative's scale.

The stock bleach was 5g of sodium ferricyanide / 5g potassium
bromide in a liter of water. (In place of the this bleach, the
bleach comprising part A of the Kodak Sepia toner may be
used.) A small volume (1 oz) was diluted with 9 parts water to
make a 1:10 dilution; the stock was also diluted 1:30 (1/2 oz
plus 14.5 oz). From these dilutions, others were made so the
dilutions tested were 1:10; 1:30; 1:100; 1:300; 1:1000 and
1:3000 (1:10 serial dilutions of the 1:10 and 1:30 dilutions).

I used two step wedges; one calibrated from 0 to 3.0 OD and
the second, 0 to 6.0 OD. I selected a contact time which
printed the higher densities (2.85 and 5.0) on Zone 8, light
grey just below the paper base. Test strips were made on G1 matte
Ilfospeed for that time, and a couple with 2X more exposure.
The test prints were bleached in the most dilute bleaches for
3 min with constant agitation and developed as usual. In the
1:30 and 1:10 baths, a time of 1 min was used and a quick dip
into water was used to remove bleach droplets before
development. The printed step wedges were then evaluated to
determine the amount of contrast reduction and the density
range printed on the "treated" paper. With no bleach or
1:3000, the range printed was approximately 1.25 OD with steps
below that pure black. With increasing bleach concentrations,
more steps are printed before the paper's D-Max is reached.

A summary of the results follows using Ilfospeed G1 matte
paper and Dektol 1:1:

Dilution: Time: Density Range Printed:
No bleach NA about 1.25
1:3000 3 1.35
1:1000 3 1.50
1:300 3 1.80
1:100 1 2.10
1:100 3 2.55
1:30 1 3.15
1:10 1 3.60
undiluted 3 >5.00

In practice, the range of a wet plate negative is determined
with a densitometer and exposed for the highlights based on
the high value OD and desired placement. The bleach
procedure doesn't alter that value much, though a 10-50%
exposure increase might be required for the 1:30 or 1:10
dilutions/range. The bleach concentration primarily determines
where the blacks will fall, and this may be fine-tuned by
varying bleaching times. Times shorter than 1 min give uneven
bleaching; longer times work best.
--
Mike in RI / Internet: ab...@osfn.rhilinet.gov
michael.gudzinow...@enest.com
​

Or an additional thread back in 2003 where someone (I believe dancqu) asks why SLIMT is ignored:

http://groups.google.com/group/rec....read/thread/6297a584787ba07a/34123f280a4de678

If you think I tried SLIMT without reading all of the archived information first you'd be wrong. I did my research ahead of time to see how viable it was for other users. Based on the positive response, well-written original articles, and relatively low requirements, I decided to actually do the work and try it on my own stuff. Turns out I would have lost a serious technique to ignorance had I just put it off or dismissed it entirely.

 

[ic-racer]

The purpose of the thread was to try and draw constructive attention to it for which it deserves and possibly have a few others start using it. If it allows them to make more successful prints or explore creative options - then it's beneficial.

Good, lets stick with this.

In terms of the paper curves, if you are not used to them then that is fine.

The utility of the paper curve on an internet forum like this is that we need to know the values in the negative when we see a print. You can scan the negative to show, but because of a myriad of issues with monitors, etc. it may not look the same to us as it does to you. Therefore, having a curve for the paper response is the only way to know what is going on, without the same person printing the negative using SLIMT and multigrade technique.

 

[ic-racer]

Thanks for posting the rec.photo stuff.

One thing that I am still curious about. In the first part it speaks in detail about contortions to the paper's curve so you do have my interest to see what is going on.

I figured since the technique has been around for so long, someone would have some curves to show how SLIMT manipulation of print contrast is or isn't unique when applied to B&W materials.

 

[Mahler_one]

I know little about SLIMT, but my respect for David and what he has accomplished compels me to try to learn more about the process. I believe that ic-racer has set down very reasonable objective criteria, and has outlined the reasons why objective data is necessary. If the process has results that are so obvious to everyone who sees prints that have been "Slimted", then there should be no hesitancy on the part of those who favor the process to subject the results to objective studies that furnish data that we can all analyze. To simply say that "the differences are obvious to any one who looks" might well be true. However, everyone cannot look at the prints at the same time, in one room, under the same conditions. Objective data removes all doubt, and strengthens the point of those who believe the SLIMPT process improves a given print that would benefit from the method.

 

[clayne]

Thanks for posting the rec.photo stuff.

One thing that I am still curious about. In the first part it speaks in detail about contortions to the paper's curve so you do have my interest to see what is going on.

I figured since the technique has been around for so long, someone would have some curves to show how SLIMT manipulation of print contrast is or isn't unique when applied to B&W materials.

Well, back to curves again (not really my intent of the thread, but nonetheless) - from the 1st post, David's original articles:

http://www.davidkachel.com/historical/cont_pt3.htm
http://www.davidkachel.com/historical/nw_strry.htm

The curves I believe are from film. I also believe you're already familiar with them from that other thread. Break out any standard paper you have around and if you're adept at measuring curves (which I believe you are), you should be able to map a particular paper with and without SLIMT.

It may be interesting for you to also do it with graded #4 paper and see how that relates to VC #4 "equivalent." Emaks K-888 is available cheaply from Freestyle and is an excellent paper. It's what I use regularly and what I used for this thread.

As pointed out a couple of times by others, the technique might be more beneficial to you if used with film itself.

 

[df cardwell]

ic-racer, and all

I mean this with affection and respect,
but we tend to alternate between joyful worship of some posts and techniques,
and severe resistance and harsh criticism of others.

The OP presented this topic as he did. Respect it. Gauge your response by how it was presented.

If you want hard data that suits YOU, get off your chair and do it.

We share a great deal here, yet if artists and engineers, beginners and old hands, become over-demanding
in their dealing with each other, our community dies.

That's it. A barely civil demand for civility.

We have our own gifts and talents. And even the smartest in our midst have something to learn.

End of sermon. Pass the plate. Be good.

 

[fotch]

Well said.

 

[Q.G.]

Yet, we mustn't let an opportunity to learn something slip away by being too civil to challence something.

If the theory behind SLIMT is flawed, discovering that alone would be valuable.
If not, knowing that would be as valuable.

If the effect, the result of SLIMT can also be achieved using much simpler and cheaper means, that too would be a bit of valuable knowledge too good to ignore.
And if not, equally interesting.

Doing something, pointing at the visible effect of what you do, and then assuming (!) a mechanism to explain that effect, is never enough.

And now that experts on the topic have met in this thread, i'd say let it rip. Let's get to the bottom of it!

 

[2F/2F]

ic-racer: I'd love to see a pot of gold with a beautiful woman handing it to me as I exit my door each morning for work - however, not gonna happen. The beauty of an open forum like this is that if you'd like to see different examples of how something works you have the power to do that and the power to provide your own findings back into the thread - complete with scanned prints as I did.

I'm not going to go and burn a box of paper because you can't be bothered.

Now in reference to the other thread - it was particularly on concepts of combined baths, etc. You went at it with your densiometer, other people got involved, and it nose-dived quickly. I feel this thread actually allows us to reexamine the overall concept of SLIMT again - as it's being ignored by the majority of darkroom printers is a plain shame.



Please see paragraph above to ic-racer. I'm not going to burn a box of graded paper just to "prove" something to you guys, honestly. Because at this point you and a few others have already approached this thread as critics - disclaiming it's usefulness.

The example I gave you is a straight print on #4 with Selectol 1+2. Since I have the neg still in the carrier I may be able to do you a #2 print with no other local modifications to show a "sane" baseline. I don't have #1 paper.



You should know that exposure can easily control this. I chose that print as the one I liked best because I was fine with a rather "bright" print that could convey the overall group as best as it could. I didn't have a #2 comparison print at the time to choose against. In short you should expect less contrasty highs and less contrasty shadows, overall flatness, and still no way to fit it all in without heavy local work (which is more than SLIMT work).



I think you're arguing this in a perverse way. I'm giving you a pathological combination of scene, negative, and paper - to show that with that BAD combination of materials - SLIMT is able to pull out quite a usable print. What is not understood there? If anything that's telling you that in a relatively "bad cases" this method is fairly easily able to get you something workable.

If you're going to tell me that printing it on MG, jumping through the acrobatic hoops of split-grade printing, dodging/burning/etc. is EASIER than immersing a piece of paper in a bleach bath for 1 minute and developing as normal, then I don't know what to tell you.

I am sorry, but we simply cannot see what the SLIMT is really doing in your picture unless you match the high tones. It is as simple as that. The SLIMT print is too much lighter over all for us to judge what effect the special process is actually having. Until the high tones match in the standard-processed print and the SLIMT-processed print, the examples are doing your argument no service. Please quit being so defensive. I am not saying anything you have paraphrased me as saying. I want to see quality examples; that is all. I am just asking you to actually show us what the process does, and what it does compared to other methods of lowering contrast, which you have as of yet not done.

As for "Please see paragraph above to ic-racer. I'm not going to burn a box of graded paper just to "prove" something to you guys, honestly. Because at this point you and a few others have already approached this thread as critics - disclaiming it's usefulness," well, I am sorry again. If you want to prove that we "should be using" SLIMT (an insanely bold statement), then you are going to need to prove it to us. What is the point of making the argument in the first place if you do not want to prove anything?

Obviously the technique does something. Obviously we can use it. However, we really don't know just what it does, to what degree, or even what a print with matched high tones looks like when run through this process, based on what you posted. You published too early, before the necessary work was done to make your argument. You seem to take this line of criticism as a personal attack and a dismissal of the technique, but it is neither. I am criticizing the information provided, and asking for more information. That is all.

 

[2F/2F]

As for "fuggem". No, if he doesn't publish, he doesn't lose anything. I have been published on four continents in numerous languages in a dozen periodicals over 70 times. What I got for that is that a few of you recognize my name (and some consider me a target).

There is no money involved that doesn't make paper hat wages look EXTREMELY attractive. There is no ticker tape parade. There is no applause and there are no prizes. Mostly there is just deafening silence, occasionally shattered by someone who either did not read your article at all, or read it and entirely failed to grasp it. And then there are those who are so jealous and desperate for attention they feel they have to discredit you at any cost. I have never told anyone this before, but a former, now deceased, contributing editor to D&CCT actually threatened the editor with resignation if the magazine published one of my articles because it exposed (not by name but by empirical proof) some of his ideas as foolish. The editor did not bend, the article was published and the person in question did not resign. In short, there is a lot of grief and very little incentive indeed and my original point was that a lot of very valuable information is never made available to the photographic community precisely because of the kind of behavior exhibited in this thread. You can say that people should have thicker skins all you like, but the loser IS and always will be the photographic community. The secret keepers lose nothing. They already possess the valuable information. People who do research have always been by nature, somewhat reclusive and thin-skinned. Saying they should be otherwise gets you nothing and is short-sighted. Then the only people who might share what they know with you are those few like me who have teeth and enjoy the taste of blood! ;-)

Thank you for the information about the articles.

It is simple to me: Writers cannot be afraid. Period. They have to just deal with the world, and if they cannot, then they do not deserve to be heard, and should not be allowed to complain. The world, and people stink. We know this to be true, and we know that nothing we do will change it. We just have to survive it. As I said before, people are idiots, and we all just have to deal with it if we wish to live a productive life. I am not going to suffer the complaints of or feel sympathy for a writer who will not publish because he or she lets what anyone else thinks matter so much. We have extraordinary liberties of press, and people want to piss them away because of personal insecurities. Use them or lose them, folks. When you censor yourself out of fear or intimidation, you are letting Fascism creep in. So, fuggem!

 

[Ian Grant]

Interesting. Mees & James (Theory of the Photographic Process, 1955) certainly thought the latent image was being bleached. Are you aware of subsequent research with which I am not familiar? I have read EVERY edition of Mees & James, and virtually every publicly distributed technical photographic tome of significance from 1850 thru the mid 1980s. I have seen no references to your theory. Perhaps it is something new?

I don't suppose it matters because the effect is there regardless, but can you provide any references for your contention? Please post quotes and sources. Have you personally tried bleaching unexposed paper and then exposing and processing it?

If you are correct this provides an interesting new twist and may actually lead to additional flexibility in SLIMT techniques. You don't actually say what you contend the Pot Ferr is doing to the silver halide crystal. What do you believe is taking place? (Again, quoted references please.)

David, the important issue is that both the Sterry effect and SLIMT work, but as I said before because the Sterry effect works when you pre-treat an emulsion prior to exposure it can't possibly be bleaching the Latent image and excess Dichromate is washed out prior to drying and exposure.

I don't have a late copy of Mees so I can't look at what he's assuming takes place. I guess I would have originally looked up the Sterry process in L.P. Clerc's 1937/8 “Photography, Theory and Practice” the English edition of ""La Technique Photographique"", edited by the late George E. Brown and the Focal Press "Encyclopaedia of Photography" a late 60's edition. Both books are back in the UK so I can't see what they suggest is happening.

So we need to look elsewhere for an explanation of what's taking place.

If you take a print or negative and bleach it a Potassium Ferricyanide, Potassium Bromide bleach 1% of each then wash and redevelop it (in room lighting) to completion it will be restored to the same densities.

If you do the same but with little or no Bromide the redeveloped print will be substantially lighter and won't reach the same densities and the overall contrast drops. The same happens when Sepia toning and in both cases the shadow details (prints) are affected far more than the highlights when the bromide level drops (The Control of Colour in Indirect Toning Methods, Dr Schweitzer, Foto Round. 1938 / BJP Almanac 1939). There's no new latent image until re-exposure.

So in the Sterry process the Dichromate, or SLIMT the Ferricyanide is acting on the Silver halides in the emulsion and affecting the development process, some halide must be being displaced.

One problem of the original Sterry process is the drop in emulsion speed but some of this can be recovered by further treatment prior to exposure. (Need to find the reference)

Potassium Dichromate can also be used to increase the contrast of an emulsion, by treating in a solution containing Hydrochloric acid for 2 minutes, then washing & drying prior to exposure. Again there's a loss of emulsion speed. (BJP Almanac, 1910)

Potassium Dichromate 11 to 22 gms
Hydrochloric Acid (conc) 3.5 ml
Water to 1 litre

So we have an interesting new twist, showing the absence or presence of halide is the key to Contrast.

Ian

 

[davidkachel]

David, the important issue is that both the Sterry effect and SLIMT work, but as I said before because the Sterry effect works when you pre-treat an emulsion prior to exposure it can't possibly be bleaching the Latent image and excess Dichromate is washed out prior to drying and exposure.

I asked you for quotes and references and whether or not you had tried this yourself.. nothing. I don't believe you are correct and all the literature says you are not. You insist on this speculation without any evidence whatsoever and in contradiction to all the evidence in existence. In Mees & James they specifically mention using these bleaches to study distribution between surface and internal latent image. This was done all the time. Mees & James SAID THEY WERE BLEACHING LATENT IMAGE. YOU say they were not, but you provide no proof. If you were correct, obviously their results would have shown it because it would have made their study impossible. Instead they consistently got the data they sought, one emulsion after another, proving them right and making your supposition improbable to say the least. I am certainly open to new ideas but you have provided nothing. If you are so certain of this, go in the darkroom and prove it! However, your results would mean nothing unless the bleach were washed completely from the paper prior to exposure. Residual bleach would of course result in a false positive. I no longer have a darkroom or I would do it myself. I encourage others here to do this very simple test to put Mr. Grant's mind to rest, once and for all. But remember to wash the paper after bleaching and before exposure to an absurd degree to ensure that all bleach is removed from the paper.

I don't have a late copy of Mees so I can't look at what he's assuming takes place. I guess I would have originally looked up the Sterry process in L.P. Clerc's 1937/8 “Photography, Theory and Practice” the English edition of ""La Technique Photographique"", edited by the late George E. Brown and the Focal Press "Encyclopaedia of Photography" a late 60's edition. Both books are back in the UK so I can't see what they suggest is happening.
Ian

As I said earlier, if it was important and written between 1850 and the mid-1980's, I've read it. My lungs are full to this day with whatever it is that lives inside the inventory of rare book stores and the locked shelves of University libraries. I know the books you refer to well and there is no discussion of contrastwise or speedwise bleaching in either. They may mention the Sterry Method, but if there was anything of significance, I would remember. Before Mees & James, no one knew how the Sterry method worked. If they had, someone would have invented SLIMTs before I did. ONLY the 1966 edition of Mees & James mentions anything of significance about contrastwise and speedwise bleaching and they were either ignorant of the Sterry method or didn't think it important to mention. (Earlier I said 1955; brain spasm I guess).

Now, the best minds of the 20th century say that latent image bleaching does in fact, bleach latent image. Yours is the one and only voice claiming that it does something else, but you refuse to say what that something is, or provide any evidence whatsoever for your contention. Until such time as you can do so, please remain silent on the subject.

 

[Thomas Bertilsson]

Thanks to Clayne for posting, and for David to further explain.

I am embarrassed to confess that I was not aware of the SLIMT technique, but can't wait to try it out. It seems like a very interesting technique that will add to my array of tools to deal with situations where I screwed up or might even want to improve a print.

So thanks to both of you - I value your contribution very highly.

- Thomas

 

[Ian Grant]

so, please remain silent on the subject.

David, way back I told you I've tried & tested both the Sterry process (70's) and SLIMT (90's), and so I know they both work.

Perhaps the confusion over whether there's Latent image bleaching taking place come about because the Sterry process was typically used to control film contrast, after exposure, just prior to development. It can be done before or after exposure, but with films it's best done after for another reason which becomes obvious.

The British Journal (Photograpy) Colour supplement of 1st October 1909 has a short reference to the use of the “Sterry method” by Dr Drake-Brockman with Autochrome plates to control high contrast, using a 30 second preliminary bath in a 1% Dichromate solution prior to first development. The film loses it's “colour” sensitivity in the Dichromate because he indicates development can now be done by an Orange light.

So for film use the Sterry process was used after exposure & before development but with paper it can be done prior to exposure, batches of paper treated washed and dried under safelight conditions. I've done it and made numerous prints (well over 100) back in the 70's.

Perhaps we are talking at cross purposes because whatever reactions are taking place are affecting how the latent image is being developed, and the presence of the Silver Dichromate or Ferricyanide complexes is the cause whether formed before or after exposure, and in either case leads to a reduction in speed and contrast. That doesn't contradict anything you say Mees has written, they've chosen to call it Latent Image Bleaching.

We know from any good book on Photographic Chemistry, Mees, Mason, Glafkides, Clerc etc that there's an equilibrium reaction between Silver Halides and Ferricyanides which is used to control image colour in toners. SLIMT is using the same equilibrium reaction, I gave you a reference for that, but again there's so many bleach formulae published that show clearly that less Bromide and more Ferricyanide leads to warmer toned images.

Agfa published 3 alternative Re-halogenating Bleaches, in Agfa Rezeptes, 1960 (and numerous other editions), varying the ratio of Ferricyanide to Bromide, in most respects the re-halogenated silver is then similar to to the silver halide in a unprocessed paper albeit slower.


Agfa 500

Water . . . . . . . . . . . . . . . . . . . . . 360ml
Potassium Ferricyanide 10% . . . . . . 600ml
Potassium Bromide 10% . . . . . . . . . 40ml


Agfa 502

Water . . . . . . . . . . . . . . . . . . . . . 400ml
Potassium Ferricyanide 10%. . . . . . . 500ml
Potassium Bromide 10% . . . . . .. . . . 100ml


Agfa 502

Water . . . . . . . . . . . . . . . . . . . . . 190ml
Potassium Ferricyanide 10% . . . . . . .300ml
Potassium Bromide 10% . . . . . .. . . . 500ml
Ammonia (s.g. 0.91) . . . . . . . . . .. . 10ml


So Agfa are varying the ratios w/w of Ferricyanide/Bromide from 15:1, 5:1 and 0.6:1, the higher the Bromide the colder, denser & more contrasty the final tones, the reverse where there's very little Bromide and a vast excess of Ferricyanide, very much warmer tones considerably less density and contrast. On a molecular level those ratios are 5.42:1, 1.81:1 and 0.22:1 quite substantial differences in an equilibrium reacxtion.

This shows extremely clearly, & uncontroversially that Silver Ferricyanide is the key to final density & contrast, which is exactly what you are exploiting with SLIMT. The only difference with a Toner is the Re-developer - Thiourea or Sulphide fogs the latent image, but that "Latent Image Bleaching" as Mees calls it is still there

As the re-halogenation takes place effectively before re-exposure this would seem to indicate that SLIMT would work used pre-exposure as well. However it would be pretty pointless to add the additional washing and drying before exposure.

Finally David, I am NOT disagreeing with the SLIMT process.

What I'm absolutely certain of is that treatment with Ferricyanide or Dichromate also works prior to a latent image being formed because I've used it with the Sterry process and it's used all the time with Toners. Maybe we have to accept that the term "Latent Image Bleaching" is misleading but you and I didn't coin it.

Mees would have been well aware of the Sterry process, he knew George E. Brown the Editor of the BJP who like Mees was a Chemist, Mees contributed formulae to the magazine & Almanac while at Wratten & Wainwright, and was also an advertiser. While at Kodak both Harrow & Rochester Research facilities published papers in the BJP under his leadership.

Ian

 

[ic-racer]

Break out any standard paper you have around and if you're adept at measuring curves (which I believe you are), you should be able to map a particular paper with and without SLIMT.

.

Ok that is fair. Seriously I did not want to do this if you or David alread had some curves to post. This [making and posting some curves of what SLIMT does to paper] does sound like an interesting thing to do if we don't already have the infornmation.

I'll tell you my interest lies in trying this SLIMT with MG paper and comparing to the 'less than straight' full-yellow exposure curves posted by N. Lindan a while back. Maybe SLIMT will make it worse, maybe it won't do anything, maybe it will straighten out the curve.

See the light blue line ("00 filtration") in this graph of Nicholas' :http://www.darkroomautomation.com/support/mgivfbwtd72hd.jpg

For the lurkers: "Why am I interested in "00" performance of MG paper???"
1) To imitate paper response of platinum or Azo using multigrade paper, and if so, potentially having easier control over contrast by altering filtration.
2) To improve the aesthetics of long tonal range negatives (related posts here: (there was a url link here which no longer exists))

 

[eclarke]

Amazingly, you can spend only $6-7 on film and $6-7 on paper and make some decisions about this. I always make 2 sheets of every subject and this method doesn't have to be used as a sledgehammer, it can also be a delicate massage when the first sheet isn't perfect. You can talk about it for months or try it in an hour and the amount of chemicals it uses in really tiny....