Shadows sit on the toe. Their exposed crystals develop fully within the first few minutes.
Highlights sit on the straight line and shoulder. They continue gaining density as long as development continues.
Extending development raises the highlights much more than the shadows. Therefore, development controls contrast rather than overall density.
| Notation | Development | Effect |
|---|---|---|
| N−2 | Substantially shortened | Contracts by two zones |
| N−1 | Shortened by about 25 per cent | Contracts by one zone |
| N | Normal | Unchanged |
| N+1 | Extended by 30 to 50 per cent | Expands by one zone |
Exposure determines shadow placement. Development sets the highlight values.
Reading and Fine-Tuning
- Empty shadows: under-exposure
- Blocked highlights: over-development
- Flat negative: under-development
- Dense throughout: over-exposure
High dilution produces a compensating effect. The developer exhausts locally in dense highlights, allowing shadow development to continue. For instance, developing for 10 minutes rather than standard times requires careful dilution.
Common pitfall: using development to rescue exposure. Extending development does not recover empty shadows. It only increases highlight density and grain.