A proportional reducer is a chemical solution used in photographic processing to reduce excess density and contrast in a negative in a controlled manner. By selectively diminishing darker areas without affecting the lighter tones proportionally, it helps restore balance and detail to overexposed or high-contrast negatives.
This technique is valuable in darkroom photography, particularly when working with film that has been exposed under challenging lighting conditions. Using a proportional reducer allows photographers to improve image quality, enhance tonal gradation, and produce more visually pleasing prints from otherwise difficult negatives.