What chemicals are used for developing?

• A. phenidone-hyrdoquinone or metolhydroquinone
• B. Silver nitrate and ammonia
• C. Hydrochloric acid and ethanol
• D. Sodium thiosulfate only

Answer: (A)

Development in photographic processing uses reducing agents that convert the exposed silver halide into metallic silver, forming the visible image. Phenidone paired with hydroquinone or metol paired with hydroquinone are classic developer formulations because they work together to balance speed, contrast, and grain: one component accelerates development while the other helps control tone and detail.

The other options aren’t developers. Silver nitrate and ammonia relate to the emulsion’s composition and silver chemistry but aren’t the active reducing agents used in development. Hydrochloric acid and ethanol are solvents or stabilizers, not substances that develop the image. Sodium thiosulfate is the fixer, which removes unexposed silver halide after development, not part of the development process.