Developer
The chemical solution that converts exposed silver halide crystals into metallic silver, making the latent image visible.
Measured in
minutes at °C
In depth
A developer selectively reduces crystals carrying latent image specks while leaving unexposed ones alone, and its formulation shapes the result profoundly: fine-grain developers dissolve crystal edges at a small cost in speed, high-acutance ones exhaust locally at edges to increase apparent sharpness. Time, temperature, dilution and agitation together determine contrast.
Examples in practice
The same negative developed in a fine-grain solution and a high-acutance one produces visibly different edge sharpness.