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hmmm... mastering all those films is an insanely well done job : http://www.dr5.com/blackandwhiteslide/filmreviewdev1.html
@138S You can't really adjust fogging reexposure, it's not practical.
Yeah, David Wood is masterful ! He has been at this game for decades
Yes... not easy in a non continuous processing, in the complex kodachrome processing it was done 3 times...
Problem is that when totally fogging film the second developer develops the "silver reserve" producing fog, and any path to reduce that fog will decrease DMax.
If we were able to not fog the silver reserve that silver reserve would only develop (in 2nd dev) from infectiouos development in the extreme shadows, delivering deeper blacks...
it is a way I'm exploring... not sure if it will work, I plan a test it throwing controlled lux·second on the bleached film, the idea is increasing DMax without increasing DMin, I plan to do it with contact copies of the Stouffer wedge, so it would be easy to test. If it works it would be easy to do it with sheets, for rolls a "device" would be necessary.
@138S Assuming that you can give a precise reexposure, in order to avoid dense highlights, I can't see any way of avoiding weak Dmax. If you are getting foggy highlights, then there's a chance that you aren't exposing enough in camera. Or perhaps the contrast after first development is weak and you need to extend FD time. Or you used too little potassium thiocyanate, or sodium thiosulfate. And let's not forget that a typical BW film has a relatively dense, tinted base, which isn't ideal for highlights in BW slides.
but still I have to learn a lot to make optimal slides for projection.
exactly. !!!3 decades !!!
I wonder if it wouldn't be easier to do it the old movie industry way -- expose and process for a good negative, then rephotograph or contact print the negative to get a positive (equivalent to making a darkroom print, except too small/too fast to do any significant dodging and burning). There are film stocks made specifically for this, like Kodak 5302 Fine Grain Release Positive.
@138S You have a comprehensive set of formulae for what is almost certainly the Scala process in US6350563.pdf. Use them (don't bother with the HQ free formulae). Use the bleach in EP1006408B1 if you don't want to handle dichromates. All the chemicals (or reasonable substitutes) are available in home-user quantities. There's no need for further aimless speculation unless those formulae really fail to work at all. If they are good, you should purely need to alter the first developer time to zero in on correct process time. Agfa's photo engineers knew what they were doing, especially given that it was a fully commercialised process. I have a scanned example of CMS 20 run in Scala if that's of any use to you?
Still, IMO, nailing the BW reversal processing is a great workflow,
A slide capable film must be able to have all of the negative silver developed in the first developer or there will be film left to form a gray image in the highlight areas of he positive. If the film in question has a fair amount of undeveloped grains in normal reversal first developer, then those grains can develop in the second developer.
To combat this, a first developer is usually a "foggy" developer with a silver halide solvent present to force total development of silver in negative dmax areas. Then the second developer can go to completion without causing gray highlights.
If these conditions are not met, then the film is not a good candidate for making slides at all.
PE
While it's fun trying to make reversal work for any film, these sage words of wisdom by PE suggest that a sensible choice of film, first developer and halide solvent goes a long way in getting good results.
Then, LOL, see that David Wood can process it with optimal results:
copper sulfate (Anhydrous ) is the ideal solution.I agree! making contact copies on release film (or other) is the most powerful way, having the opportunity to make the adjustments we want, we still have the negative to make prints and we only have to make those slides that are worth in the roll.
Still, IMO, nailing the BW reversal processing is a great workflow, it commands a remarkable effort to nail the slide because we have a single opportunity to do it , but it also sports authenticity because there is no possible manipulation. This is an emotional value, perhaps...
Those are quite interesting docs !!!
For CMS 20 nor dichromate nor permanganate bleach are to work. Both metallic silver and halide are totally cleared in a few seconds, delivering a totally clear frame. I tried to dilute a lot dichromate and permanganate, but by when metallic silver is cleared a lot of damage is made in the halides, this is what I could obtain (with diluted bleach) after Ps edition, the frame was very thin and not suitable for projection:
View attachment 243488
Well, at least it has a vintage look...
Probably those pro lab process CMS 20 slides with another bleach. Copper way is known to work... or perhaps they use some C-41type bleach... what's me, I was not able to properly bleach CMS 20, I'm to try copper...
This process was only designed to work on a rotary machine (JOBO) that never worked with me manually,Please see attached document (http://www.ars-imago.com/productinfos/osbahr_reversal_films.pdf)
Page 12-13...
View attachment 243468
...shows the unused silver halide. The question is that some Pro Lab jobs (Scala, DR5) do sport a DMax vs DMin that home processing may not reach by far.
This is only a suposition, something I'm to investigate: perhaps a way to obtain an extended dynamic range for the projection is provocating a large infectious (2nd) development of the "Unused Silver" in the shadows but no development of the "Unused Silver" in the highlights.
My reasoning is: if we fog and develop all "unused silver" when we remove that density (solvent, etc) then we also decrease DMax potential... The single way I see to conserve top DMax and min DMin is infecting the "unused silver" in the shadows and not fogging the unused silver...
Disclaimer, just trying to find an explanation for the Pro Lab vs Home yield difference, just speculating while preparing to check it.
It could be an issue of fine tuning the first developer and halide solvent which Ilford might not have attempted to do for the two films you mentioned. Some people have complained that Ilford's recommendation of 8-12g of Thiosulphate per liter is too much.
This process was only design
ed to work on a rotary machine (JOBO) that never worked with me manually,
I don’t know, maybe I was wrong about something, I’m currently reviewing myself.
Raghu, that PE recommendation is very good. This is the reason why an energic Paper Developer is recommended in most recipes.
Anyway see this "We do not recommend reversal processing HP5 Plus or DELTA 400 PROFESSIONAL film as results are likely to exhibit unacceptably low contrast." This is said by Ilford in his Reversal instructions !!!!
https://www.ilfordphoto.com/reversal-processing/
Then, LOL, see that David Wood can process it with optimal results:
"The most popular film for dr5 simply because of its image quality @ higher iso speeds. Like most of the ILFORD films, HP5 is great for bringing out shadow the detail, especially when you need to scan those dark areas in the image. The "BEST" quality if your needing speed; 320-3200iso exposure latitude. Speed lower than 320iso is not recommend for this film, though it is possible. HP5 produces an old fashion image quality, similar but smoother than TX.
HP5 holds detail in the brightest whites and deepest blacks. For many, It is the favorite film for dr5. DMAX is around 3.45 @400iso "
http://www.dr5.com/blackandwhiteslide/hp5dev-1.html
___________________________________________
My HP5 reversal processing is quite good, still I have to enhace DMin to a lower value. My guess is that I've something to learn.
Note that it uses Metol, not Phenidone/ Dimezone etc (quite atypical for Agfa) and has two different kinds of sulfite in it
Well, metol has REDOX 20, IIRC, which is crazy high compared with other agents. It is a powertool to drill into "unused silver" for the highlights, but this solves only a half of the problem.
Let me reiterate the problem I find when working the shadows, after bleaching, if we fog all remaining halide, we still have the "unused silver" fraction that will fog the frame to a certain level, any strategy we use to clear that fog will also damage DMax, isn't it?
Where is that AGFA patent?Quoting the Agfa patent:
"At the same time, the first development must not be too active and thereby result in an increase in fogging, since this results in decreased maximum densities after reversal development."
In other words you want the lowest possible fog yet still be able to develop all the silver. This is likely why an accelerator was chosen over a more traditional silver solvent.
Where is that invention patent?
Quoting the Agfa patent:
"At the same time, the first development must not be too active and thereby result in an increase in fogging, since this results in decreased maximum densities after reversal development."
In other words you want the lowest possible fog yet still be able to develop all the silver. This is likely why an accelerator was chosen over a more traditional silver solvent.
For this reason paper developers are often used as first developer. From Darkroom Coobook:
"While paper developers should always contain some restrainer, when formulating a film developer it is better to decrease the accelerator rather than add more restrainer."
Regular film developers are less suitable than paper developers...
or perhaps they use some C-41type bleach... what's me, I was not able to properly bleach CMS 20, I'm to try copper...
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