Thanks, David, for relating your experience at the BBC, who clearly take colour vision seriously. The Ishihara is OK as an initial test and those that achieve an all-correct score are unlikely to have colour vision problems; they have passed both colour recognition and shape recognition. For those that achieve more of a mixed score it is appropriate to refer them to another test such as the Farnsworth. This is, as you relate, a tough test, but if it were not tough it would not be much good. My general view of any test, as one who spent a chunk of my career in education, is that if eight participants out of ten score 100% it is not much of a test.

Thanks, David, for relating your experience at the BBC, who clearly take colour vision seriously. The Ishihara is OK as an initial test and those that achieve an all-correct score are unlikely to have colour vision problems; they have passed both colour recognition and shape recognition. For those that achieve more of a mixed score it is appropriate to refer them to another test such as the Farnsworth. This is, as you relate, a tough test, but if it were not tough it would not be much good. My general view of any test, as one who spent a chunk of my career in education, is that if eight participants out of ten score 100% it is not much of a test.