English: Crumey (2014) https://doi.org/10.1093/mnras/stu992 Fig. 3. Threshold increment versus background luminance for various target diameters (in arcmin). Data from tables 4 and 8 of Blackwell (1946).
Crumey (2014) https://doi.org/10.1093/mnras/stu992 Fig. 3. Threshold increment versus background luminance for various target diameters (in arcmin). Data from tables 4 and 8 of Blackwell (1946).