Amorphous carbon films were deposited on glass by d.c. magnetron sputtering from a graphite target in mixtures of argon and hydrogen. Hydrogen flow and other deposition parameters affected the optical and mechanical properties of these films. Increasing hydrogen content caused the average visible transmittance to vary from 16% to 86% for 500-Å thick films. Maximum compressive stress and hardness occur between 0-1% hydrogen flow, resulting in rapid delamination. Low sputtering power moderately increases transmittance and hardness while relieving stress. Transparency is induced in both the high-hydrogen and low-power films by formation of sp³ C-C bonds. In the case of the hydrogenated films, however, a softer polymeric structure is formed.