Abstract
A flicker photometer is described which is specially designed to fulfil the conditions requisite to accuracy and precision in the use of such instruments. The photometric field subtends 2° at the eye and is surrounded by a steady white field which subtends 25°. Special attention has been given to minimizing the loss of light, so that the high field brightness employed in flicker photometry can be obtained without bringing the illuminants unduly near the photometer head.