N+ or N- development times are still perfectly possible for those zone system workers wishing to exercise tight control of tonal contrast, but the need for this is much reduced. For ultimate control of negative density for individual film emulsions, and for even greater solution economy, single bath processing is available, and the 'spread' of suggested development times for varying films is narrower than conventional developers. This means developing differing film emulsions together for the same time is frequently a practical proposition.

DiXactol™ achieves this by a different approach and unique formulation. It is the only commercially available solution to combine conventional two bath development, which in itself holds back the overdevelopment of negative highlights while it builds up shadow detail, with tanning staining, and ultra high definition developing agents. The tanning of the gelatine containing the film emulsion occurs in direct proportion to the varying exposure received by differing areas of the negative - the more the exposure, the more the tanning. This tanning inhibits the ingress of developer to the emulsion. Therefore heavily exposed highlight regions of the negative are restrained in development while development continues in the lesser exposed shadow areas. The tanning also helps prevent the softening of definition common with fine grain development and helps resist emulsion abrasion. Along with the use of the sharpest known developing agent at high dilution to form boundary effects, the result is outstandingly high definition. Halation around heavily exposed areas of images (such as windows in an architectural interior, or lights in a night-time picture) is also especially well controlled.

The natural oxidisation of the solution absorbed into the emulsion in the first bath during activation in the second bath (or simultaneously with development in the single bath option) causes a further vitally important effect - a brown stain with hints of yellow/green in proportion to the level of exposure in each area of the negative. The emulsion of both graded and variable contrast papers is largely "blind" to this colour, as in a safelight, and it acts as printing density. The result is that the negative needs less actual development of the silver, so the grain is lessened even further and definition further enhanced. A DiXactol™ negative will look thin to the human eye, but will print with far more body than would seem likely because of the printing density of the stain. The stain in some tanning developers can be markedly yellow/green, and varies greatly among various film types giving inconsistent printing characteristics. The yellow/green colour also affects variable contrast papers by softening their contrast. Sometimes this is a useful characteristic, but often it isn't, giving unpleasantly distorted tonal rendering. The colour produced by DiXactol™ is much more consistent across film types, and gives predictable tonal distribution on graded and variable contrast papers. The effect of the stain differs, however, when printing on these different types of paper. On graded paper the stain acts purely as extra printing density thus making the negative more contrasty than visual inspection might suggest.

On VC papers the stain also acts to soften contrast slightly. Since the stain is greater in the highlights than the shadows, this means that there is an automatic softening of highlights while shadow contrast is relatively unaffected. This can be very useful in the automatic 'masking' of highlights with a tendency to block up, such as windows in architectural interiors or clouds in landscapes. Users will find an approximate difference of one grade between the same negative printed on graded and VC papers.

Furthermore, the stain occurs in the gelatine between the clumped grains of silver in the negative which are actually quite prominent in this high definition developer. Since the stain acts as printing density, the effect is at least to partially fill the spaces between the grain clumps when printing. The result is a smoothness of tonality that renders delicate highlights such as mist with a new level of almost 'liquid' reality usually spoiled by the grain of conventional developers.

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