old light values (I only tested scalar) need to be switched back to values they had before the global gamma correction thing was introduced!
example: when I first made the material tester scene, there were two lights: one with a value of 29, one with a value of 2.4
When I corrected the scene to work with global gamma correction, I needed to change the light values to 29^(1/2.2) and 2.4^(1/2.2).
Obviously this was a bug, which is now corrected, but beware that if you use global gamma correction and want to render old scenes, multiply your lights as following:
x= y^g
where x = new value
y = old value
g = gamma value