Divided developers

Divided developers are used for what is known as either divided or two-bath development. Divided development allows a photographer to expose roll or sheet film under many different and difficult situations and still create printable negatives because of the compensating action inherent in the process. 

Another advantage is that the cost of developer per roll of film is much less than with single-solution developers. A safe number of rolls of film to develop using one liter of the first bath is twenty, as long as the solution is not contaminated or does not oxidize. The second bath, which contains the less expensive chemicals, should be discarded after processing ten rolls of film. Divided development can be used for all films except document films (for example, Rollei ATP ). 

When formulating a divided developer the addition of sodium bisulfite to the first bath will help prevent oxidation. The rule is to make the preservative approximately 20% bisulfite (for example, D-23 Divided Developer requires 100.0 grams of sodium sulfite instead use 80.0 grams of sulfite and 20.0 grams of bisulfite). 

Technique of Divided Development In divided development, two separate baths are used. The first bath contains the developing agent(s), restrainer, and preservative. The second bath contains the accelerator. The second bath is used to activate the developer. Borax is the least active accelerator metaborate is about double the strength of borax carbonate is about double the strength of metaborate. Hydroxide is the most active of the alkalis and the least controllable. 

The temperature of development is not as critical for divided development as singlesolution processing, but for best results, keep the temperature of all solutions the same, between 68F/20C and 80F/27C. 

Water bath development is similar to divided development. Both methods are useful for reducing overall contrast while maintaining density in the key shadow areas. 

There are two major differences between divided and water bath development. The first is agitation. In divided development, agitation takes place in both the first and second baths. In water bath development, the film is gently placed into the second bath and left without motion for two to three minutes. 

The second difference is that divided development is a once-in, once-out process once in A, once in B, rinse, then fix. Water bath development is meant to be a repeatable process. After immersion in the second bath, the film is returned to the A bath and the process repeated as many times as necessary to achieve the desired contrast or density. For this reason, water bath development is best used in conjunction with development by inspection. 

This is one of the best divided developer formulas for fine grain and full tonal scale. For the first bath you can use classic D-23 or a modified version, given here. This is because when... 

This formula can also be used as a divided developer. To use as a two-solution developer try 4 minutes at 68F/20C followed by 3 minutes in a 2% borax solution. Use intermittent agitation in the first solution and gentle but continuous agitation in the second solution. This will prevent uneven development, especially with 120 roll film. For higher contrast lighting, increase exposure and shorten the time in the first solution. 

Let us look back one last time. We have divided development into four stages Begin, Design, Develop and Exploit. In each of these there were four or hve lessons as is summarized in Figure 1. In development these lessons follow each other roughly. There is nearly always some backtracking - and sometimes a lot. Just to recall, we summarize each lesson in one or two sentences. 

Different development environments (D) are at the origin of variations in software reliability. Boehm (1981) divides development environments into three categories ... 

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