>>2975325about luminance.
on astia and provia the peaks on the spectral dye curve are the same meaning they have the same brightness. compare to ektar the peaks are not equal ie blues are rendered most luminous, then greens, then reds, then yellows.
my take is that, say this photo
>>2975143, which has some dark shadow areas and a bright blue sky, astia would work better than ektar because the blue sky would be the sky would be less luminous and more saturated. you
>>2975129 would be interesting to see the same shot on a fuji stock 