The Stoeckler Two-bath Film Developer

By James M. Kates (jkates@audiologic.cirrus.com), 10 September 2000
for the Large Format Page

INTRODUCTION

The effective use of the Zone System (Adams, 1968; White, 1968; White et al., 1976) for black-and-white photography requires a film developer that can be used to adjust the contrast of the negative. The negative density range needs to be reduced if the contrast of the negative image exceeds what can be easily printed on the desired paper contrast grade, and the density range needs to be increased if the contrast of the negative image is too low. Similar arguments apply to scanning a negative for digital image processing, where the density range of the negative should be matched to that of the scanner.

Expansions of the negative contrast can be achieved with many developers by increasing the development time. Contractions are more difficult, however, since reducing the development time generally leads to a loss of film speed. Thus for reduced development times with a conventional developer, White et al. (1976) recommend that the film speed be reduced to half the normal speed for normal minus one stop (N-1) development and to a quarter the normal speed for normal minus two stops (N-2) development.

A developer recommended by White (1968) for contractions is divided D-23, where D-23 is used as a first development bath, followed by a Borax second bath. White claims that the low zones in the negative attain their usual density, so greatly increased exposure times are not necessary, while the high zones above Zone VIII are brought to the required Zone VIII printing density. Adams (1968) recommends a similar two-bath developer for high-value control consistent with the Zone System. He points out that the divided developer builds maximum density in the shadows but reduces the increase in density in the highlights.

Several formulas have been proposed for divided development (Anchell, 1994; Anchell and Troop, 1999). One of the oldest and simplest is the Stoeckler two-bath developer (Jacobson and Jacobson, 1972), the formula for which is given in the next section. Stoeckler, as cited by Jacobson and Jacobson, claims the following advantages for the two-bath development:

  1. Harmonious compensation for great contrasts
  2. The effective sensitivity of the film is not materially reduced
  3. As it is development at the surface, there is less halation and irradiation, and the best possible rendering of sharpness
  4. Great economy and cheapness of the solutions

In the remainder of this paper, it is shown that the advantages of the Stoeckler two-bath developer hold even for modern emulsions. Ilford Delta 400 is used as the test film, and similar results would be expected for Kodak T-Max 400 film. The formula and development procedures are given in the next section, followed by a set of density vs. log exposure curves that are used to determine normal (N), normal-minus (N-), and normal-plus (N+) development times. A time versus temperature chart is also provided.

FORMULA AND DEVELOPMENT PROCEDURES

The formula for the Stoeckler two-bath developer is given by Jacobson and Jacobson (1972) and is reproduced in Table 1. Distilled water should be used for making the developer baths, and the chemicals should be mixed in the order given. A pinch of the Sodium Sulphite should be added to the water prior to adding the Metol to help prevent oxidation. The formula for Bath I is similar to that of Kodak developer D-23 (Kodak, 1963), except that the amount of Metol is lower. Both baths are used without dilution. While Bath I can be reused, it is recommended that both Bath I and Bath II be discarded after developing one roll of film.

The recommended development time with continuous agitation to give normal development is 5 min in Bath I and 3 min in Bath II at 20C for Ilford Delta 400 film (120 roll film). No pre-wetting of the film should be used. For development, a JOBO 2500 tank was placed on its side on a manual roller base and the film was given continuous agitation. Using a JOBO motorized development system gives virtually identical development times. The film should be transferred from Bath I to Bath II without rinsing. The recommended times in Bath I assume a diffusion enlarger and variable-contrast paper, or a digital scanner with a density range greater than 3.2; the time in Bath I for N-1 development (given later in this paper) would be an appropriate starting point for determining normal development for a condensor enlarger, a diffusion enlarger printing on graded paper, or for a scanner with a restricted density range. Different films will require different times in Bath I to achieve normal development, although the time for Kodak T-Max 400 should be similar to that for the Ilford Delta 400 film. The time at 20C in Bath II is 3 min independent of the type of film.

HOW THE DEVELOPER WORKS

There appears to be some misunderstanding as to how two-bath development works. The confusion is due to the fact that two-bath developers actually form two developer groups, based on the pH of the first bath. The first group consists of those developers that have a low pH in the first bath. Most two-bath developers fall into this group. For these developers, the low pH prevents any development from taking place in the first bath; the film only absorbs the developer. Development begins only after the film is transferred to the second bath containing the alkali. The time in the first bath is not critical as long as it is sufficient for the film to become saturated with the developer, and modifications of the negative density with changes in development time are hard to achieve.

The second group of two-bath developers has a pH in the first bath that is high enough for some development to take place in that bath. The Stoeckler two-bath and divided D-23 developers fall into this category. Both Adams (1968) and White (1968) realized that the Sodium Sulphite in Bath I creates an alkalinity sufficient for the Metol to function as a developer without the need for any additional alkali. Thus the Stoeckler Bath I is equivalent to using a Metol-Sodium Sulphite developer to develop the film, but the time is cut short, resulting in only partial development. Adjusting the time in Bath I therefore controls the development of the highlights and provides the compensating action associated with this developer. In Bath II, the developer carried over in the film emulsion reduces the silver until the developer is exhausted, resulting in maximum shadow density.

Confusion can arise if a two-bath developer in the high-pH group is assumed to belong to the low-pH group. For example, Anchell (1994), in discussing the Stoeckler two-bath developer, states that the "film is placed into the first bath where the emulsion absorbs the developing agent. Because the pH is low, little or no developing takes place." This statement is reiterated in the discussion of two-bath developers by Anchell and Troop (1999), who clearly assume that all two-bath developers are of the low-pH type. This assumption leads them to erroneously conclude that "Zone-style control is not possible with two-bath" developers. This confusion over the chemistry of two-bath developers led Anchell (1994) to recommend substituting Sodium Bisulphite for 20 grams of the Sodium Sulphite; the Sodium Bisulphite reduces the pH of Bath I so that essentially no development can take place. This substitution results in very flat negatives since the highlights can not develop properly. Thus the Anchell (1994) modification of the Stoeckler two-bath developer is not recommended. Fortunately, the formula given for the Stoeckler two-bath developer in Anchell and Troop (1999) is correct.

D-Log E CURVES

The development times recommended by Jacobson and Jacobson (1972) for the Stoeckler two-bath developer are for an earlier generation of films, and the same development times are repeated by Anchell (1994) and Anchell and Troop (1999). A new set of development times was therefore determined for Ilford Delta 400 film in the 120 roll size. A set of density vs. log exposure curves were developed for four different Bath I development times for exposures ranging from Zone 0 to Zone XI. The film was rated at ISO 400 using a Sekonic L-438 light meter; the comparable setting for a Sekonic L-508 meter is also ISO 400, but with an exposure compensation of 0.5 EV to account for the difference in the meter calibration constant. An 18-percent grey card was used as the target, and a ESECO Speedmaster SM100 densitometer was used to measure the density of the negatives.

The density versus log exposure (D-Log E) curves are presented in Fig 1. The compensating action of the two-bath developer is clearly shown in the curves. For the development times of 3-5 min, the curves overlap at and below Zone III. This indicates that the shadow density in the low zones, and hence the effective film speed, is not affected by the reduction in Bath I development time. The film absorbs enough developer in Bath I during even the short 3-min time period to completely develop the shadows after it is placed in Bath II. Above Zone III, the negative density is determined by the amount of time in Bath I. The development of the mid tones is a combination of the development that takes place in Bath I plus the additional density that accumulates in Bath II. For the highlights, the amount of developer carried over into Bath II by the film is not enough to noticeably increase the density of the silver already deposited by the development in Bath I. Thus the highlight development is determined solely by the time in Bath I. The result is a density vs. log exposure curve that is steeper for the shadows than for the highlights, thus providing the desired compensating behavior.

The D-Log E curve for the development time of 7 min is somewhat different. The development time in Bath I is now long enough to increase the shadow density beyond that which can result just from the developer absorbed by the film. Thus the slope, and the effective film speed, is increased over that obtained for the shorter development times. The density slope for the highlights, however, is still shallower than for the shadows. Overall, as the time in Bath I is increased, the two-bath development behaves more like a conventional single-bath developer such as D-23.

The Contrast Index was approximated by subtracting the density for the Zone I exposure from the density for the Zone VIII exposure, and dividing by the difference in the log exposures (equal to 2.1 for the 7-zone difference). This procedure is similar to that proposed by White et al. (1976). The results are presented in Table 2. The 5 min Bath I development give a Contrast Index of 0.73, which is quite close to the 0.7 desired for diffusion enlargers. This Bath I development time is therefore taken to be normal. The density above base+fog for the Zone VIII exposure given the development of 5 min in Bath I is 1.9. This value is approximately the density achieved for the Zone VI exposure given 7 min in Bath I, so 7 min represents N+2 development. By the same logic, 4 min in Bath I gives approximately N-1.5 development and 3 min in Bath I gives approximately N-3 development.

For convenience in adjusting the development times for different films, it was decided to have uniform steps on a logarithmic scale for development ranging from N+2 to N-2. The time steps give N+2 development as 1.4 times N development and N-2 development as 1/1.4 times N development in Bath I. On this scale, N+1 is approximately 1.2 times N and N-1 is approximately 1/1.2 times N development. This logarithmic scaling of the development times fits the 3, 5, and 7 min development data exactly and is very close to the contrast achieved with the 4 min development time.

TIME-TEMPERATURE CHART

The times for development ranging from N+2 to N-2 are presented in Table 3. The change with development time with temperature was not measured, but was instead approximated based on the information published by Kodak (1963) for D-23. Those data indicate that the development time changes by a factor of 2 for a change in temperature of 10F.

MODIFYING THE DEVELOPER

The Stoeckler two-bath developer contains a large amount of Sodium Sulfite. In this concentration, the Sodium Sulfite acts as silver solvent, giving a very smooth fine grain structure to the negative. However, the solvent action reduces the acutance of the negative because sharp edges are partially dissolved and replaced with a more uniform deposit of silver. A slightly higher acutance divided developer can be obtained by reducing the amount of Sodium Sulfite in the first bath of the two-bath developer, and then adding a small amount of Borax to restore the pH of the bath. The modified formula is given in Table 1. Development times for the higher-acutance version are the same as for the Stoeckler two-bath developer, and the D-log E curves are very similar. The higher-acutance developer gives slightly sharper grain edges and higher acutance at the expense of a somewhat more pronounced grain structure. The higher-acutance version of the developer would therefore be recommended as the starting formula for developing Ilford Delta 100 or Kodak T-Max 100 film.

Another modification to the two-bath developer is to use a stronger alkali for Bath II. Discussions of divided D-23 (Anchell, 1994) suggest one of three alkalis for the second bath. Borax is recommended for the finest grain and lowest contrast, Sodium Metaborate for increased contrast accompanied with increased grain, and Sodium Carbonate for the highest contrast but with the greatest grain. An example of using a stronger alkali is illustrated in Figure 2. The dashed line is for the normal development time in Bath I and using the 1-percent Borax solution for Bath II. The solid line is for a reduced development time in Bath I (approximately N-1), but using a 4-percent Borax solution for Bath II. The development using the 1-percent Borax solution has an approximate Contrast Index of 0.66, while the 4-percent Borax solution yields an approximate Contrast Index of 0.67 . Despite the similarity in Contrast Index values, the two curves are different. The increased strength of the alkali in Bath II results in increased density in Zones VIII and below, while the reduced development time in Bath I results in decreased density in Zones IX and above. Thus adjustments to the alkalinity of Bath II and the development time in Bath I can be used to modify the contrast and compensation characteristics of the Stoeckler two-bath developer. Further modifications of the Stoeckler two-bath developer suggested by Anchell and Troop (1999) have not been tested, and no comments can be provided as to their effectiveness.

CONCLUSIONS

Two-bath development is an effective procedure for negative contrast control. The Stoeckler two-bath developer is one of the few that gives usable contractions as well as expansions. The formula and time-temperature table give the information needed to use the two-bath developer for Ilford Delta 400 (120 roll film), and provide a starting point for experimentation with other modern films such as Kodak T-Max 400. An investigation of the D-log E curves showed how the developer functions. The time in Bath I controls the development of the highlights and also provides partial development of the shadows. Transferring the film to Bath II allows the shadow areas to develop to completion. This two-stage development results in a wide range of contrast control in the negative, and makes the Stoeckler two-bath developer very attractive for practitioners of the Zone System. The developer formula can also be modified to provide a trade-off between fine grain and acutance, and adjustments to the development time in Bath I and the alkalinity of Bath II can be used to change the contrast and compensation characteristics of the two-bath developer. Thus the Stoeckler two-bath film developer leads to a family of developers that can be matched to the specific characteristics of the film, subject, and printing technology.

 

 

REFERENCES

Adams, Ansel (1968), The Negative: Exposure-Development, Morgan and Morgan, Hastings-on-Hudson, NY

Anchell, Stephen (1994), The Darkroom Cookbook, Focal Press, Boston

Anchell, Stephen, and Troop, Bill (1999), The Film Developing Cookbook, Focal Press, Boston

Jacobson, C.I., and Jacobson, R.E. (1972), Developing: 18th Revised Edition, Focal Press, London

Kodak (1963), Processing Chemicals and Formulas: Sixth Edition, Eastman Kodak Co., Rochester, NY, Professional Data Book, Publication J-1

White, Minor (1968), Zone System Manual: New Revised Edition, Morgan and Morgan, Hastings-on-Hudson, NY

White, Zakia, and Lorenz (1976), The New Zone System Manual, Morgan and Morgan, Dobbs Ferry, NY

 

 

 

 

Stoeckler Two-Bath Developer

Bath I

 

Water (125F)

750 ml

Metol

5 grams

Sodium Sulphite, anhyd.

100 grams

Water to make

1 liter

   

Bath II

 

Water (125F)

750 ml

Borax

10 grams

Water to make

1 liter

 

 

Table 1. Formula for the Stoeckler two-bath developer (from Jacobson and Jacobson, 1972)

 

 

 

 

Figure 1. Density vs. log exposure for Ilford Delta 400 (120 roll film) developed in the Stoeckler two-bath developer using continuous agitation.

 

 

 

Bath I Time at 20C

 

3

4

5

7

Contrast Index

.53

.63

.73

.86

 

Table 2. Approximate Contrast Index as a function of the time in Bath I for Ilford Delta 400 (120 roll film).

 

 

Table 3. Development time in minutes for different degrees of negative contrast as a function of temperature for Ilford Delta 400 (120 roll film) developed in the Stoeckler two-bath developer using continuous agitation. Normal development assumes a diffusion enlarger and variable-contrast printing paper.

 

 

 

Slightly Higher Acutance Divided Developer

Bath I

 

Water (125F)

750 ml

Metol

5 grams

Sodium Sulphite, anhyd.

50 grams

Borax

2 grams

Water to make

1 liter

   

Bath II

 

Water (125F)

750 ml

Borax

10 grams

Water to make

1 liter

 

Table 4. Formula for the slightly higher acutance divided developer.

 

 

 

 

 

Figure 2. Density vs. log exposure for Ilford Delta 400 (120 roll film) developed using 1 percent and 4 percent Borax solutions for Bath II. The time in Bath I was 4:00 at 22 deg C for the 1 percent solution, and 3:30 at 22 deg C for the 4% solution.

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