Area light

What does the button Gamma “realy” do or how does this function influence the lamp?
The tooltip only talkes about “Sets the light gamma correction”, which is - unfortunatly and often seen in Blender`s tooltip- a tautology.

The Gamma result isn’t updated in the buttons-window preview. If you change the Lamp type (to say Hemi) then back to Area, or click the Energy slider it’ll update. Sort of like (but the reverse of) Buffer Shadows, if you set Gamma to less than 1.00 the lighted pixels “spread” less light to contiguous pixels, and greater than 1.00 will spread more (and eventually have a ‘washout’ effect on crisp detail. You can drop the Energy value to compensate for the washout though).

The light isn’t evaluated per pixel though but along intersecting points of an invisible grid that relates to the Size and Rect/Square values of the lamp itself.