視力表の視標の評価（第1報）—写真視力表による視力と光束発散度との関係に及ぼす視標の形の影響

Test types in visual acuity determination.:Report 1. Visual acuity-brightness relation in various Shapes of test types

　視力はいろいろの因子によつて影響を受けるが，使用する視力表によつて視力の検査結果が異る事は，実際問題として屡々指摘される所で，異る図型字型の視標では視認度の不一致を完全に避けることは出来ない。視力表に用いる視標はその視認度が，標準視標たるLandolt環の視認度に近いことがもとより望ましいが，その条件を見出すための基礎実験として写真視力表を作つて検討したので報告する。

An attempt was made to find out the best shape of the test object which gives the clo-sest values visual acuity of to Landolt's rings.

Photographs of Landolt's rings, Inoue's hooks:(reduced type of Snellen's hooks), Yamamori's 6-6 rings and Hagino's 4-dots-types were used. A series of test objects was made for each of the object, the size and the albedo being varied serially : the ratio of albedos of the test object and the surrounding field was kept constant.

The acuity-brightness relations were obtained for each series of the object using a uniform illumination.