I don't know if you have seen these charts that Fred Picker gave in Zone VI Newsletter Number 37, November, 1983...
Originally Posted by Leigh B
They get right to the Matt's original question. They involve IR and UV.
This also gives us the missing SBC photocell spectral response Matt was looking for!
Fred asserted that with Tri-X tests of 21 scenes, including natural objects such as a Cortland apple and an unripe orange, an unmodified Soligor II read 2 stops or more off in 23% of the scenes. After modification, all exposures were within 1 stop.
Leigh, you know I'm just making the specific argument that it wasn't fair to debunk Fred Picker's Zone VI modification of spotmeters using a Macbeth color checker, because it's not as good a test of natural scenes as the test Fred did.