The perception of flicker by the human eye depends upon the picture content, and this paper describes a relation between the critical flicker frequencyf_cand the spatial frequencyf_x. Provided that the visual picture is presented in such a way that each spatial component, presented at a frequencyf_p, obeys the inequalityf_p \geq f_c = f(f_x) = f_0 \exp (-k f_x), no flicker effect is perceived. The constantsf_0andkare weakly dependent upon the brightness and picture area; they are a little more strongly dependent upon the contrast ratio and the type of picture. The effect can be exploited in motion pictures or television by presenting high-quality pictures interleaved with low-quality ones. In the latter, some high spatial frequencies would be omitted. For television, band reduction of a face by 9:1 is possible. Practical consideration may reduce this compression ratio to a little short of 2:1.