Variables determining flicker sensitivity in small fields.

TLDR: It appears that the most important determiner of flicker detection in small fields is contiguity of field and surround, and both decrease of illuminance and absence of image movement reduced sensitivity at all frequencies.

Abstract: The effect of size, luminance, and image movements on detection of flicker in small centrally located fields was studied with 12°, 1°, and 2° targets at average retinal illuminances of 26, 260, and 2600 td. When these fields were viewed in an essentially dark surround, a maximum of sensitivity was found at approximately 10 Hz. Image movements had no effect in determining sensitivity to flicker, but decreasing field size led to an over-all decrease of sensitivity, and decreasing illuminance enhanced low-frequency sensitivity, while reducing sensitivity to high frequencies. The effect of an illuminated surround was assessed with a 1° field viewed in a steady surround that was either contiguous with the flickering field, or separated from it by a nonilluminated band that subtended 2′ of arc. The condition of a separated surround gave the same results as the dark surround. The contiguous-surround condition yielded a frequency-response curve that showed no clearly defined maximum. However, this condition markedly increased low-frequency sensitivity and altered the effect of luminance and image movements on flicker detection. Both decrease of illuminance and absence of image movement reduced sensitivity at all frequencies. It appears that the most important determiner of flicker detection in small fields is contiguity of field and surround.