Test type Small 320×72 Medium 640×144 Large 1024×230 Download Tiff Original 2400×539 | (118.1 KB) Description "The Actual Size of the Test Type, which shiykd be seen by the Normal Eye at a distance of Twenty Feet." — Blaisedell, 1904 Keywords a, c, e, eye, grid, test, vision, visual Galleries Miscellaneous Optics Source: Albert F. Blaisedell Our bodies and How We Live (Boston: Ginn &, 1904) 271
