All Frisby Stereo Test Present “real depth” objects viewed with natural vision: no testing glasses are required.
Each plate has four random-pattern squares with a circle of pattern elements lying in depth relative to its surround. The depth effect is due to the circle and its surround being printed on opposite sides of the plate.
The Frisby Stereo Test has 3 plates allowing for testing stereo acuity disparity as fine as 15 seconds of arc.
