> Quote - Sure - I did something like that in 2006 before Poser could read an HDR image. See the link. > > Here's an newer version of that shader, using the image from the tutorial you linked. > > The Bias Value_1 multiplier scales the LDR image (in gray scale) so some of it is above 1. Then using a low Value_2 pushes all luminance down that is below 1, and all luminance up that is above 1. > > The resulting value is used to multiply with the original colors and add some of that with the original colors. > > On the left, you see a darkened version of the result, but the sun and it's reflections are still hyper-colors, because they were way above 1.

how  could we make the shader so that we could control how bright it is? 
for example to make sometimes 2 times brighter or 5 times. so that we could type in a number?

i made here a control map.