From bernard_L: So much for my (vague) plans to try an LED lamp in my enlarger.
VC printing was set up around a tungsten source (I would think), so the ratio of dyes would have been derived accordingly. So if an LED has a different spectral distribution, I'm really not surprised by the result. I think the graded paper shows that an LED source can be a perfectly viable option. Just need to understand the response characteristics. In practice I'm not sure how much the "kink" in the VC curve would be a problem, as long as you understand the relative difference in the shadows and highlights.