Flicker effect and television compression

The perception of flicker by the human eye depends upon the picture content, and this paper describes a relation between the critical flicker frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_c</tex> and the spatial frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_x</tex> . Provided that the visual picture is presented in such a way that each spatial component, presented at a frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_p</tex> , obeys the inequality <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_p ≥ f_c = f(f_x) = f_0 exp (-k f_x)</tex> , no flicker effect is perceived. The constants <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_0</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</tex> are 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.