The construction of a readability target and its correlation with resolving power

A readability target was constructed. It consisted of sets of randomized letters which were incremented in size by the twelfth root of two. This new target and the German DIN standard legibility target were photographed simultaneously using a microcopy camera set at various degrees of magnification. Evaluation of the resultant images was done by ten observers who each viewed sixteen sets of target pairs. From this data a correlation of .90 was found between the two targets. Nine out of the ten observers found the new target easier to evaluate. A study of the new target\u27s variability was done and it was concluded that inter-operator mean values were consistent