Double reversal processing?

[Paul Verizzo]

OK, I know I have an overactive imagination, but here's what I'm wondering.

Since reversal processing of a negative winds up using the smaller silver grains for the image, what if one uses a reversed negative and then reverse print the paper?

I can think of a lot of reasons not to do this, mostly centered on difficulty, and only finer grain as a reason to do it.

Thought I would throw this out there.

 

[Pinholemaster]

Why?

 

[Paul Verizzo]

Read again?

Why?

I explained.

 

[Photo Engineer]

Grain is grain. The positioning of maximum and minimum grain patterns vary with positive and negative products but it is still there and still grain.

PE

 

[Paul Verizzo]

Reversal processing

Grain is grain. The positioning of maximum and minimum grain patterns vary with positive and negative products but it is still there and still grain.

PE

I recently read that in reversal processing the large grains that make the traditional neg image are bleached out and it is the small, slow grains that the redevelopment brings to life. That explains why I could never understand why slide films were of much finer grain than color neg for an equivalent speed. (light bulb, please!)

This is all just a hypothetical, mental, um, exercising type of proposal.

 

[Ian Grant]

Back in 1972 or very early 1973 I went to a lecture, while at university, about B&W reversal processing and reversal printing.

The essence of the lecture was the quality of B&W slides, the long tonal range and excellent image sharpness, very fine grain etc. After showing slides, the lecturer went on to explain how he made B&W reversal prints, and then displayed some. The quality of the slides and prints was superb, the lecturer claimed using the reversal process gave the highest possible quality and was better than using the traditional negative/positive process. His prints seemed to substantiate his claims.

That's the only time I've ever come across or heard of this being done, the lecturer was a student doing a research based PhD.

Ian

 

[Paul Verizzo]

At least two of us are nuts!

Back in 1972 or very early 1973 I went to a lecture, while at university, about B&W reversal processing and reversal printing.

The essence of the lecture was the quality of B&W slides, the long tonal range and excellent image sharpness, very fine grain etc. After showing slides, the lecturer went on to explain how he made B&W reversal prints, and then displayed some. The quality of the slides and prints was superb, the lecturer claimed using the reversal process gave the highest possible quality and was better than using the traditional negative/positive process. His prints seemed to substantiate his claims.

That's the only time I've ever come across or heard of this being done, the lecturer was a student doing a research based PhD.

Ian

Besides grain, can you think of any reason such a process would give "highest quality?" I would think that it would be harder to match the negative, I mean positive, to the paper. More room for mismatches and errors.

But it would be nice to examine "negatives" as a positive!

 

[Ian Grant]

Paul, I was sceptical when I was at the lecture. The crux was supposed to be the much wider latitude of the Reversal process, and this supposedly worked at the printing stage as well.

The basic problem with the whole B&W reversal/reversal print process was the very high level of skill and experience needed, and when cross examined the lecturer admitted it wasn't the most practical method of B&W print making. It would be interesting to read his research papers, I occasionally see one of the lectures from the same University department and will ask if he can remember thge PhD students name. I think the research was sponsored by Kodak (UK).

Ian

 

[Paul Verizzo]

Paul, I was sceptical when I was at the lecture. The crux was supposed to be the much wider latitude of the Reversal process, and this supposedly worked at the printing stage as well.

The basic problem with the whole B&W reversal/reversal print process was the very high level of skill and experience needed, and when cross examined the lecturer admitted it wasn't the most practical method of B&W print making. It would be interesting to read his research papers, I occasionally see one of the lectures from the same University department and will ask if he can remember thge PhD students name. I think the research was sponsored by Kodak (UK).

Ian

It's hard to imagine "wider latitude" in anything with more steps and with product curves never meant for the process. Maybe in exposure of the film? Although I can't see that either.

 

[Ian Grant]

All I can remember now was that the double reversal prints had an extremely smooth tonality, they were beautiful prints. But I'd like to see them again and re-asses the process.

I think part of the advantage was the reversal processing of the film captured a long tonal range easily, without having to use something like the Zone system or BTZ for individual images. But then printing the positives would be far more complex compared to conventional neg/pos.

It would be interesting to see if anyone else used this double reversal technique.

Ian

 

[markbarendt]

Other than cost, why not just use Ilfochrome for the print?

 

[Ian Grant]

Ilfochrome is inherently contrasty, and wouldn't give a particularly good print. It would offer no advantages over conventional B&W paper reversal processed. It's also only available as an RC paper.

Ian

 

[AutumnJazz]

I've heard that BPD in Britain does good B&W Ilfochromes. I've been meaning to get some done, but I haven't.

There's also an Efke positive paper that is processed in regular B&W chemistry.

 

[Ian Grant]

Possibly the best company to use for B&W printing of B&W positives (slides) would be Ilford/Harman Texchnology. Although they only offer prints from negatives, they would have the technology to produce the highest quality B&W prints from positives.

Ian

 

[Photo Engineer]

I recently read that in reversal processing the large grains that make the traditional neg image are bleached out and it is the small, slow grains that the redevelopment brings to life. That explains why I could never understand why slide films were of much finer grain than color neg for an equivalent speed. (light bulb, please!)

This is all just a hypothetical, mental, um, exercising type of proposal.

It remains hypothetical to me until proven!

No, grain is grain. The appearance of grain in slides and negatives take place at different points on the scale but when prints of negatives are made, the grain of the print and the grain of the slide are in the same place and, negative is slightly better due to the nature of reversal processes.

PE

 

[dr5chrome]

..i dont know,, ive experienced this since '91. reversing B&W film is absolutly sharper, 4-5x. Guess 17 years doesn't hold much water.

Cibachrome prints from monotone chromes are not less than spectacular. Contrast can be controlled by an experienced printer.

Reversal processing, film or prints, takes expertise. it is not for the faint of heart. The outcome is worth the effort, if you want to take the effort to do it.

dw

 

[Photo Engineer]

..i dont know,, ive experienced this since '91. reversing B&W film is absolutly sharper, 4-5x. Guess 17 years doesn't hold much water.


dw

The negative film has a contrast of about 0.6 and the reversal film has a contrast of about 1.8, therefore to the eye the reversal film appears sharper. By actual measurement they may be equal or the negative may actually be sharper.

The eye is very easy to fool and many equate higher contrast with higher sharpness due to the difference in tone between two subject items in a photo.

Then again, a particular developer can be chosen which can act detrimentally on the negative and beneficially on the reversal film. You can inadvertantly "set up" a situation which proves your point. Under controlled conditions with instrumentation to measure the results, the negative image will generally be sharper. If the reversal is sharper you will find that any sharpness was introduced by the negative developer for the most part, as the reversal development generally goes to completion.

PE

 

[Paul Verizzo]

So there is more to my idea than being crazy.

..i dont know,, ive experienced this since '91. reversing B&W film is absolutly sharper, 4-5x. Guess 17 years doesn't hold much water.

Cibachrome prints from monotone chromes are not less than spectacular. Contrast can be controlled by an experienced printer.

Reversal processing, film or prints, takes expertise. it is not for the faint of heart. The outcome is worth the effort, if you want to take the effort to do it.

dw

I can understand your prejudice from your handle. Not that that's bad.

Why would reversal images be sharper? The grain issue makes sense, but I'm lost on the sharpness issue.

 

[Photo Engineer]

Grain is highest where the grains are larger. In negatives, that is the toe of the curve, and in positives it is the shoulder. You can visually see the negative grain in the toe more easily.

But..... Here is the big caveat, when you make positive prints, the grain is in the shoulder on all types of print regardless of source and is thereby less visible due to density - or more visible depending on the range of your tone and exposure, but it is in the high density regions.

Negative films impress sharpness on the image by edge effects and absorber dyes. Reversal films do the same, but then the second development stage takes development to completion and cannot (in most cases) change the edge effects already there. Therefore, reversals have the same or weaker sharpness to comparable negatives.

Now, here is the final catch. A neg pos print places the print on the straight line mid scale as per design, but a pos pos print places the print on the entire slide curve catching both the toe and shoulder. Therefore two things happen in a pos pos print. First, you compress detail and get that 'dupey' look and secondly you get the full impact of the grain. In a negative you are printing in the mid tones of the negative and can avoid the full impact of grain which is mainly in the curved part of the toe.

You have to remember that neg pos is designed for printing, but pos pos is not unless the camera film is of a special design. The original of a good pos pos print system is very low contrast, and not pleasant when viewed by projection. In any case, you lose detail in pos pos printing.

This can be shown visually via the characteristic curves and also can be proven mathematically. I doubt if anyone wants to see either here. In any case, I doubt if I'm up to the latter anymore, but just consider than any print is the result of the product of the gamma at any point on the curve so that a negative system prints with a constant film value and a variable paper value. A pos pos system prints with variable gamma from both materials and therefore is similar to a .jpeg image in that it severely compresses the data and is therefore "lossy".

PE

 

[markbarendt]

You smart guys amaze me.

It just boggles me how little I really know.

 

[Ian Grant]

Have to totally disagree with Dave, dR5, about the difficulty of B&W reversal processing, it's actually remarkably easy and straight forward.

There are commercial kits avaialble, Kodak made one for Reversal processing Tmax films, and Ilford/Harman Technology publish information for reversal processing on their website.

In addition to that there are a lot of well known formulae available in a variety of publications, for instance the Pathé B&W reversal process - which must have been used for many miles of Cinema newsreels.

An area that hasn't been fully explored is the effects of using different 2nd Developers, particularly to alter the image tones. This can be done with direct development or by bleaching & redevelopment later. (dR5 do offer an alternative warm option).

Something that has been forgotten is that the first developer in a B&W reversal process contains a strong silver solvent, usually Thiocyanate, this will give exceptionally fine grain, Kodak did a lot of research and Patented developers of this type.

Ian

 

[Photo Engineer]

The solvent in the best first developers is used to enhance sharpness and achieve fine grain kind of like Microdol but better. You can use solvents more easily as any dichroic fog is removed by the process. There are a whole series of extremely effective solvents. Kodak MP first develoers use a whole arsenal of patented addenda IIRC and they have a number of first developers available for different purposes IIRC.

You are absolutely right Ian.

PE

 

[Lowell Huff]

The secret to great imaging in reversal processing is in the first developer. To creat the best image, the first developer must be a "long scale" continous tone compensating developer. The second key to revesal processing is using a chromate-sulfuric acid bleach.

 

[dr5chrome]

Mr. Grant;

I tire of your debunking our process and abilities to reverse film. I am sure you are a great guy and I surely want to put an end to your highly skeptical attitude. I have done this before and oddly none have taken us up on the offer. So here it is again...

You shoot as much film as you like, send it over to us and ill process it free and send it back to you, free. You may then provide your critique here, good or bad. Ill even except poor exposures as an excuse. It is not fair of you to judge dr5 based on never having tested it. I make this offer to anyone on this forum, so there ya go.
Seeing is believing but several of our clients are here as well, Gavin Smith comes to mind.

dr5 is not like the Ilford process! It is not the Kodak kit either. DO NOT lump us in with these other inferior processes please.

regards

dw

Have to totally disagree with Dave, dR5, about the difficulty of B&W reversal processing, it's actually remarkably easy and straight forward.

There are commercial kits avaialble, Kodak made one for Reversal processing Tmax films, and Ilford/Harman Technology publish information for reversal processing on their website.

In addition to that there are a lot of well known formulae available in a variety of publications, for instance the Pathé B&W reversal process - which must have been used for many miles of Cinema newsreels.

An area that hasn't been fully explored is the effects of using different 2nd Developers, particularly to alter the image tones. This can be done with direct development or by bleaching & redevelopment later. (dR5 do offer an alternative warm option).

Something that has been forgotten is that the first developer in a B&W reversal process contains a strong silver solvent, usually Thiocyanate, this will give exceptionally fine grain, Kodak did a lot of research and Patented developers of this type.

Ian

 

[Ian Grant]

Please could you tell me where I have ever de-bunked your abilities to run the dR5 process. I have absolutely no interest in whether your process is good, bad or indifferent, so have no intention of ever trying it.

I'm sure you run a good commercial B&W reversal service and I don't doubt your abilities. Like any B&W processing it's the fine tuning that produces the highest possible quality.

However B&W reversal processing is not rocket science, there's plenty written about the subject, a great many published formulae, and it is well within the capabilities of many photographers to produce extremely high quality B&W slides. Sure they may well need to tweak the parameters of the process to achieve the quality of Scala, or your own process, but it isn't difficult.

Probably the most informative technical data from any manufacturer on Reversal processing was published by May & Baker (ow Champion) in the late 60's or early 70's and related to the commercial use of their Suprol developer for automated reversal processing. Anyone reading this would have the capability to fine-tune the process to achieve their desired results.

None of the other published B&W Reversal processes is inferior or superior to your dR5 process, they are different and in the right hands most are just as capable of producing high quality results.

Ian