Sorry, don't know any way to do that, unless a Python script could work - have no idea if that's possible.

I can think of several good reasons why ambient and diffuse are set 20 apart though. Like to keep people from making dead black shadows by default, because of the drastically limited dynamic range of monitors (maybe 100:1, compared to human vision of 30,000:1). Or the fact that radiosity rendering needs lots of ambient.

Like you, i usually tweak those setting or change the contrast slider. Being able to change all materials in one setting would be very handy. Let's request a feature at e-on's web site (the more who do, the more likely it'sll happen).

e-on feedback center

_jc
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