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In the last week I have been spending my spare time reading Barry Thornton’s excellent book ‘Edge of Darkness’ and which as you will discover from my spiel further on, this title is very apt, although it could have just as easily been called ‘Edge of the Light’.
Although there are various things in the book that made me question how I had been doing things for the past 30 years or more, there was one part in particular that made me sit up and really pay attention, this was the bit about how a much slower development with greatly reduced agitation, can, with the correct type of developer (this bit is important) increase apparent edge sharpness (acutance) and reduce grain. He also went on to explain how over enthusiastic agitation whilst shortening development times can actually give rise to a large increase in the amount of grain and the lowering of the acutance (apparent edge sharpness), neither of which is particularly welcome in the search for making a good negative suitable for the making of a truly ‘fine print’ (surely the holy grail for exponents of film photography).
So what actually is ‘acutance’, it is the ‘apparent increase’ in edge sharpness between high contrast areas in an image. It also appears on areas of not so high contrast but the effect is much lower although again this will lead to an apparent increase in sharpness between these areas.
So, how does this work?
By increasing the development time and reducing agitation the developer has more time to work ‘on the areas’ it is in contact with. Where these areas are of high contrast, the developer in the less exposed area of the emulsion is drawn across into the area of greater exposure thus lowering the amount of development in the less exposed area (slightly) and increasing the amount of development in the more exposed area (again slightly) thus creating a slightly greater contrast especially at the EDGES (hence the title of the book) where the light and dark areas meet than is actually captured at the moment of the exposure. Another benefit to this is in the reduction of the amount of grain ‘clumping’ together. So, a win-win situation, unfortunately, like everything in life it is not as easy as just that, and there are other steps that have to be taken or adjusted in order to get close to the best out of a given film emulsion.
Some other little gems that this book has furnished me with this week is that most photographers overdevelop their films using the adage of ‘I’ll just give it a minute more to make sure’, I have definitely been guilty of this in the past, ‘fast films are less sharp and have more visible grain) than slower more contrasty films’ not actually always true as it is very dependant of how the films are handled by the photographer and the most important was that the manufacturers ISO ratings for their films were only a guide and often the film is underexposed as the manufacturers tend to want to overstate their films ISO to the high limit rather than at the ‘best’ figuratively speaking.
So, back to the original topic; I started to search the internet for details on how best to process a Kodak Tri-X 120 sized film I had already exposed at ISO400 in the Mamiya C330f and again I began to discover some things that again I had believed were written in stone. The first of these was that Kodak and I understand many other film manufacturers now suggest that their modern Black & White (not C41 though) film emulsions be processed at 24° Centigrade rather than the 20° Centigrade I had always believed the optimum. This apparently allows the emulsion to react better with the chosen developer and reduces development time (oh, hang on a minute, I want to increase development times to increase the acutance of the images on the film, this may well not be a good thing). The other thing that doesn’t help the emulsion is chemical shock, when the emulsion which is coated in an overly alkaline solution (developer) suddenly becomes coated in an acid solution (stop bath) to prevent further development to take place (this alkaline/acid step is required more when the developer has a greater strength {low dilution factor} and at a higher temperature {greater chemical reaction}, again this is not something we really want to hear), another fact discovered at this time was that all chemicals should be tested and adjusted where required as different results will be obtained with different tapwaters (I should have known this as I am the Asset Manager of 7 Water Treatment Works and none of them produce chemically similar water to the others), where possible, distilled water should be used and this will circumvent the above issues.
So aside from all the other variables: testing own film speed, using a specific developer, clip testing films, using a densitometer and a plethora of other things I decided to utilise my current (open bottle of Ilford LC29) developer and attempt to work out a dilution and time that would give me a reasonable negative when processed at 24° Centigrade.
My normal film processing regime (and has been for a long long time) is at 20° C with Ilford LC29 (the developer has changed over the years) @ a dilution of 1:19, 8 minutes development (6.5 minutes recommended with a rotary processor), as I was inversion processing (constant agitation for first 30 seconds followed by 3 inversions every minute) I increased the time by 0.5 minutes plus a minute just to be sure (as quoted above), 30 sec Stop Bath, 30 sec wash, 4 minutes Fix and 5 minutes washing with water changes every 30 seconds and constant agitation, so:
Dev 8 minutes @ 1:19 and 20° C (constant agitation initially and 3 inversions every minute thereafter)
Stop 30 seconds
Wash 30 seconds
Fix 4 minutes
Wash 5 minutes
I now had to change the development time to allow for a higher temperature, this came out at 5.5 minutes at a temperature of 24° C, I then had to adjust for a different dilution which I chose 1:39 and gave this double the time of 11 minutes. For agitation, I inverted the tank 3 times as soon as the developer had been introduced and then only inverted once every 3 minutes afterwards. This gave the following process steps all at 24° C:
Dev 11 minutes @1:39 and 24° C (3 inversions initially and one inversion every 3 minutes thereafter)
Water Rinse 30 seconds initially and then another 30 seconds with fresh water
Fix 4 minutes
Wash 5 minutes
So, what are the results like: They are I believe without any doubt, the best negatives I have ever processed. They have a full range of tones, there is tremendous detail in the shadows, the grain is really well managed and uniform and they look like they would be easy to print, they were certainly easy to scan. We have to remember in all this, the negatives were as is and previously shot at the manufacturers ISO400 light readings were taken with a Weston Euromaster II in reflective mode as I could not get into a position that would allow me to use the invercone, with a developer that is not recommended for use at that dilution (especially with Tri-X), and whilst I changed the LC29’s dilution and development time I only used normal tapwater to make up my dilution, a developer with a Metol base should really be used for this technique(such as Ilford’s Perceptol).
I hope those of you that use film will find my finding’s interesting and may lead to you trying your own experiments in processing techniques, the fun for me is just beginning. My sincere thanks to Barry Thornton.
Full image:
Half Full sized image 6000x6000
100% Crop
100% Crop of shadow detail
Although there are various things in the book that made me question how I had been doing things for the past 30 years or more, there was one part in particular that made me sit up and really pay attention, this was the bit about how a much slower development with greatly reduced agitation, can, with the correct type of developer (this bit is important) increase apparent edge sharpness (acutance) and reduce grain. He also went on to explain how over enthusiastic agitation whilst shortening development times can actually give rise to a large increase in the amount of grain and the lowering of the acutance (apparent edge sharpness), neither of which is particularly welcome in the search for making a good negative suitable for the making of a truly ‘fine print’ (surely the holy grail for exponents of film photography).
So what actually is ‘acutance’, it is the ‘apparent increase’ in edge sharpness between high contrast areas in an image. It also appears on areas of not so high contrast but the effect is much lower although again this will lead to an apparent increase in sharpness between these areas.
So, how does this work?
By increasing the development time and reducing agitation the developer has more time to work ‘on the areas’ it is in contact with. Where these areas are of high contrast, the developer in the less exposed area of the emulsion is drawn across into the area of greater exposure thus lowering the amount of development in the less exposed area (slightly) and increasing the amount of development in the more exposed area (again slightly) thus creating a slightly greater contrast especially at the EDGES (hence the title of the book) where the light and dark areas meet than is actually captured at the moment of the exposure. Another benefit to this is in the reduction of the amount of grain ‘clumping’ together. So, a win-win situation, unfortunately, like everything in life it is not as easy as just that, and there are other steps that have to be taken or adjusted in order to get close to the best out of a given film emulsion.
Some other little gems that this book has furnished me with this week is that most photographers overdevelop their films using the adage of ‘I’ll just give it a minute more to make sure’, I have definitely been guilty of this in the past, ‘fast films are less sharp and have more visible grain) than slower more contrasty films’ not actually always true as it is very dependant of how the films are handled by the photographer and the most important was that the manufacturers ISO ratings for their films were only a guide and often the film is underexposed as the manufacturers tend to want to overstate their films ISO to the high limit rather than at the ‘best’ figuratively speaking.
So, back to the original topic; I started to search the internet for details on how best to process a Kodak Tri-X 120 sized film I had already exposed at ISO400 in the Mamiya C330f and again I began to discover some things that again I had believed were written in stone. The first of these was that Kodak and I understand many other film manufacturers now suggest that their modern Black & White (not C41 though) film emulsions be processed at 24° Centigrade rather than the 20° Centigrade I had always believed the optimum. This apparently allows the emulsion to react better with the chosen developer and reduces development time (oh, hang on a minute, I want to increase development times to increase the acutance of the images on the film, this may well not be a good thing). The other thing that doesn’t help the emulsion is chemical shock, when the emulsion which is coated in an overly alkaline solution (developer) suddenly becomes coated in an acid solution (stop bath) to prevent further development to take place (this alkaline/acid step is required more when the developer has a greater strength {low dilution factor} and at a higher temperature {greater chemical reaction}, again this is not something we really want to hear), another fact discovered at this time was that all chemicals should be tested and adjusted where required as different results will be obtained with different tapwaters (I should have known this as I am the Asset Manager of 7 Water Treatment Works and none of them produce chemically similar water to the others), where possible, distilled water should be used and this will circumvent the above issues.
So aside from all the other variables: testing own film speed, using a specific developer, clip testing films, using a densitometer and a plethora of other things I decided to utilise my current (open bottle of Ilford LC29) developer and attempt to work out a dilution and time that would give me a reasonable negative when processed at 24° Centigrade.
My normal film processing regime (and has been for a long long time) is at 20° C with Ilford LC29 (the developer has changed over the years) @ a dilution of 1:19, 8 minutes development (6.5 minutes recommended with a rotary processor), as I was inversion processing (constant agitation for first 30 seconds followed by 3 inversions every minute) I increased the time by 0.5 minutes plus a minute just to be sure (as quoted above), 30 sec Stop Bath, 30 sec wash, 4 minutes Fix and 5 minutes washing with water changes every 30 seconds and constant agitation, so:
Dev 8 minutes @ 1:19 and 20° C (constant agitation initially and 3 inversions every minute thereafter)
Stop 30 seconds
Wash 30 seconds
Fix 4 minutes
Wash 5 minutes
I now had to change the development time to allow for a higher temperature, this came out at 5.5 minutes at a temperature of 24° C, I then had to adjust for a different dilution which I chose 1:39 and gave this double the time of 11 minutes. For agitation, I inverted the tank 3 times as soon as the developer had been introduced and then only inverted once every 3 minutes afterwards. This gave the following process steps all at 24° C:
Dev 11 minutes @1:39 and 24° C (3 inversions initially and one inversion every 3 minutes thereafter)
Water Rinse 30 seconds initially and then another 30 seconds with fresh water
Fix 4 minutes
Wash 5 minutes
So, what are the results like: They are I believe without any doubt, the best negatives I have ever processed. They have a full range of tones, there is tremendous detail in the shadows, the grain is really well managed and uniform and they look like they would be easy to print, they were certainly easy to scan. We have to remember in all this, the negatives were as is and previously shot at the manufacturers ISO400 light readings were taken with a Weston Euromaster II in reflective mode as I could not get into a position that would allow me to use the invercone, with a developer that is not recommended for use at that dilution (especially with Tri-X), and whilst I changed the LC29’s dilution and development time I only used normal tapwater to make up my dilution, a developer with a Metol base should really be used for this technique(such as Ilford’s Perceptol).
I hope those of you that use film will find my finding’s interesting and may lead to you trying your own experiments in processing techniques, the fun for me is just beginning. My sincere thanks to Barry Thornton.
Full image:
Half Full sized image 6000x6000
100% Crop
100% Crop of shadow detail
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