Pseudo-isochromatische Tafeln für die Prüfung des Farbensinnes
A German medical test book of pseudo-isochromatic colour plates, published in Berlin in 1883 by T. Fischer under Jakob Stilling, for examining people's colour vision. The pictures are mosaics of irregular blobs in muted greens, pinks and reds, with a numeral or figure hidden in the dot pattern, so the design is built from clusters of shapes that read only through colour contrast and could suggest camouflage or dot-based textures.
