Why use divided development?

[swmcl]

When you could be using 'contrastwise film bleaching' ...

Contrastwise film bleaching as explained by David Kachel et. al. involves bleaching the film after exposure and before development. It is achieved by using a very weak dilution of potassium ferricyanide which sounds highly toxic but I believe is not nearly so.

One simply immerses the film into the bleach with full agitation for a number of minutes. The result is a film response curve that is laid down to achieve a lower contrast ratio. I believe the process is entirely proportional to the amount of exposure. A slight loss of film speed should be countered during exposure.

As I understand it, a CI of between 0.4 and 0.5 is easily achieved. Thus a photograph with a more extreme SBR range can be accommodated for traditional printing methods with this process.

Similar outcomes can be had with divided developer techniques. Of particular interest is the Divided Pyrocat process which, by all accounts, produces wonderful results. Simply using Diafine is another well-known divided developer.

The difference is that the concentration of the Pyrocat in the Divided Pyrocat process is commonly 15:300 which is about 5 times what others use in a rotational process at 3:300. This makes the Divided Pyrocat process pretty expensive.

The other difference is also that a divided process is strictly a 'stand' process which is not possible with daylight tanks unless you want to completely fill a 3005 or 3006 for example !! More than a litre at 15:300 is extreme.

I suspect the answer to this question might be something to do with the range of results. For example, perhaps the contrastwise bleaching can't produce N-5 development as well as the Divided Pyrocat process ??

Cheers,

Steve

[David Karp]

I have used Diafine, Divided D-76, and Barry Thornton's variant of Divided D-23. The divided development process helps to ensure that you don't blow out the highlights in high contrast scenes, while at the same time preserving shadow detail.

Divided development is not strictly a stand process. I have used it with hangers and tanks, a slosher, and in JOBO Expert Drums. Anchell and Troop recommend using rotary development with divided developers.

[Greg]

Following advice from an article in VIEWCAMERA magazine, use divided development with Diafine to produce negatives (as David stated not to blow out the highlights) that are easily scanned to produce digital negatives for Pt/Pl printing. Have been getting excellent results by just reading Zone II to determine my exposure. FYI: For real extreme ranges of light, tried shooting digitally with HDR combining the exposures and making digital negatives to print with... resulting Pt/Pl prints were very artificial looking and I no longer go down that road.

[sanking]

Steve,

If you have not already seen it, please look at the article on divided Pyrocat that I added to the PyrocatHD web site a couple of years ago. http://pyrocat-hd.com/html/TwoBathPyrocat.html

Bleaching and re-development can be used to reduce (or increase) the density range of film negatives. The problem with this method is that if anything goes wrong you lose your negative.

Divided development is, IMO, the best method to use for scenes of very high contrast, and also works nicely for all scenes where the intention is to scan and process the files digitally.

Divided development is not done with stand development, at least not with Pyrocat. In fact, with sheet film the best method I found was rotary development in drums, with continuous agitation. With roll film I developed with the film on stainless steel reels, in tanks, with intermittent agitation.

Sandy

[Steve Sherman]

Divided Pyrocat for me did not provide the necessary negative density to directly print to the Silver wet process. I have no experience with the negative bleaching process.

I can however speak to regular success with Extreme Minimal Agitation and the Semi-Stand technique in controlling contrast ranges requiring N - 5 as well as N - 6 lighting situations.

I have come to learn controlling the extremes of Contrast in either direction yield the most dramatic adjacency effects over continuous agitation. Further, to realize success with N - 5 or 6 is an ever so delicate balance of developer exhaustion relative to agitation frequency and the length of time one is able to exploit this phenomenon. I do believe the technique I have refined can control via the wet process extremes of small or huge amounts of Contrast that few working film photographers can lay claim too.

[swmcl]

OK so I look to be wrong about an absolute need to use a stand development but I trust the requirement to use 5 times the concentration of developer (part A of Pyrocat-HD) still stands ?

I use Pyrocat-HD at 5-5-300 with FP4 and may need to back it off a little with HP5 as it is a little too reactive at 5-5-300 so I am inclined to hear Steve Sherman saying it didn't achieve negative densities. I do also have Diafine.

Can the Pyrocat-HD part A be re-used like Diafine ? Probably not (even during the one processing session of a few ours) as it oxidises ?

Steve what equipment do you use for Extreme Minimal Agitation ? I'm using 4x5 and 5x7 sheets.

Cheers,

[Doremus Scudder]

When you could be using 'contrastwise film bleaching' ...

Contrastwise film bleaching as explained by David Kachel et. al. involves bleaching the film after exposure and before development. It is achieved by using a very weak dilution of potassium ferricyanide which sounds highly toxic but I believe is not nearly so. ... I suspect the answer to this question might be something to do with the range of results. For example, perhaps the contrastwise bleaching can't produce N-5 development as well as the Divided Pyrocat process ??

Cheers,

Steve

I've been using the SLIMT (Selective Latent Image Manipulation Techniques) described by David Kachel for years for extreme contractions.

This is not bleach/redevelop (which I also use from time-to-time to increase contrast), rather a treatment of the exposed negative in a very dilute ferricyanide/bromide solution immediately prior to development. I find that I actually retain more effective film speed with extreme contractions than by using changes in time and/or dilution. I can easily go down to N-5 if needed, though I rarely have to. Since the latent image bleaching occurs proportionally, it is the highlights that are most bleached, reducing contrast there most, and retaining more separation in the low values.

The real trick to this technique is calibrating it. I'd start with trying to find a good N-2. Choose an appropriate subject and make a slew of negatives; at least 4, but 6 would be better if you're starting from scratch. Then extrapolate from Kachel's articles or whatever to find a starting point for the SLIMT bath (I'm using about 3.5 min in a 0.01% ferricyanide solution for TMY in PMK). After the ferri treatment, transfer the negative to the developer and develop nomally. Measure densities and/or print on grade 2 and then refine your SLIMT time. There will be different times and dilutions (I use from 0.005% to 0.02%) for different contractions, and film/developer combination. Most of my SLIMTs are done with "Normal" developing time, but for extreme contractions I'll use them in conjunction with reduced development, e.g., N-1 development time plus SLIMT to get N-4.

SLIMTs coupled with a reduced agitation regime (although I don't reduce agitation anything like Steve Sherman does) gives me easily printable negs with lots of edge effects.

Best,

Doremus

[Steve Sherman]

OK so I look to be wrong about an absolute need to use a stand development but I trust the requirement to use 5 times the concentration of developer (part A of Pyrocat-HD) still stands ?

I use Pyrocat-HD at 5-5-300 with FP4 and may need to back it off a little with HP5 as it is a little too reactive at 5-5-300 so I am inclined to hear Steve Sherman saying it didn't achieve negative densities. I do also have Diafine.

Can the Pyrocat-HD part A be re-used like Diafine ? Probably not (even during the one processing session of a few ours) as it oxidises ?

Steve what equipment do you use for Extreme Minimal Agitation ? I'm using 4x5 and 5x7 sheets.

Cheers,

I use 4x5 film for testing, personal shooting films are 5x7 and 7x17 done in vertical free standing tubes, one sheet at time.
Pyrocat is so inexpensive, even though Sandy King says it can be reused a second time I do not. Film processing for me is very exact, especially given the lighting conditions I find myself in so one less variable to me is a big plus, and that second run of film thru developer would amount to a variable I don't want to deal with.

[sanking]

Do not confuse divided development with stand and other minimal agitation methods. Both methods work well, but each is designed to address a specific need and the dilutions and techniques required are quite different for the two mehtods.

OK so I look to be wrong about an absolute need to use a stand development but I trust the requirement to use 5 times the concentration of developer (part A of Pyrocat-HD) still stands ?

A 1+20 dilution of stock concentrations A and B are about normal for an average CI of about .55, but it varies quite a bit by emulsion, as you can see in the CI charts for different films that accompany the article at the Pyrocat web site.


Can the Pyrocat-HD part A be re-used like Diafine ? Probably not (even during the one processing session of a few ours) as it oxidises ?

This depends on method of development. If you are developing two rolls of 120 film in a tank with 1000 ml of a 1+20 working solution you can re-use the solution 4-5 times if all of the development is done the same day, or in a 6-8 hour period. However, if you are using a minimum of working solution for rotary development in a tube (say 75 ml for a sheet of 4X5 film), the solutions should be used only once and discarded.

There may be minor variations in CI with re-use of the working solutions, but please remember that my recommendation for divided development is for a work flow where the negatives will be scanned and worked in PS, not for a work flow in which the negatives are printed directly. With scanning low CI is desierable, and minor variations in contrast are quite acceptable when the image file will be processed for final contrast.

The advantage of divided development, IMO, as I express in the article, are as follows.

This article on the use of Pyrocat as a two-bath developer is directed primarily to those photographers who expose and develop film for scanning, not for those who print optically with analog methods. Pyrocat, when used as two bath developers, is capable of extreme compensation, and no loss of film speed. Regardless of the contrast of the scene you simply expose for the deepest shadows where you want texture or detail, then develop the film in two-bath Pyrocat. The result should be a negative with good shadow detail, a linear straight-line curve, and highlights that are well within limits for scanning with a consumer type scanner like the EPSON V700. This is about as close to a “silver bullet” in film developing as I have found.

Compared to the use of Zone and BTZS type methodology there are several advantages of two-bath Pyrocat for the scanning work-flow:

1. Field work is simplified because there is no need for note taking to identify individual sheets for SBR or N type development, as in BTZS and Zone methodology. The only requirement is that the negative be correctly exposed for the shadow values where texture and detail is desired.

2. All negatives of the same film type can be developed together for the same time and temperature. In fact, in most cases even different films can be developed together.

3. The negatives will develop to a fairly low average gradient, which reduces grain and optimizes sharpness. The appearance of grain is finer because grain is dependent on contrast and density; the higher the contrast and density, the more pronounced is the grain. And, developing to a lower contrast optimizes resolution because it minimizes halation and irradiation. Photographers who use 35mm and medium format are well aware of the importance of developing to a low contrast to minimize grain and enhance sharpness.

4. Negatives developed to a low average gradient scan very well, even with consumer flatbed scanners.





Sandy

[tgtaylor]

I've read, but have not tried, that uranium toner will increase a negatives density.

Thomas