せん光露光量計

抄録

An instrument for measuring the guide number of an electronic flash equipment is described. It is essentially an integrating photometer but incorporates a self drift compensation circuit and a logarithmic converter, so that the range of the instrument can be extended to from about 6 to 100 in guide number (for an ASA 100 film). The instrument is provided with a single range indicator having a linear scale in F number steps. The calibration is carried out by means of a standard electronic flash light source whose repeatability in successive flash is better than 0.015 step. Tests on two among thirty instruments which have been produced up to now proved that the accuracy and repeatability of the instrument are better than 0.1 and 0.05 steps respectively.