11/16/2007

11-16-07 - 2

I put up floatdd in the exe section. It's the little float gamma+exposure test I was talking about yesterday. I put some new funny rational exposure functions in that I think are pretty neat. It's purty, it's pointless, whatever it was fun. The general form of rational exposure is :

x * ( a + b * x ) / ( 1 + c * x + d * x * x )

As x -> 0 , this is (a * x) ,
As x -> inf , this is b/d , then you have some other parameters to play with shape.

(a) of something like 6 to 16 makes sense. The slope of sqrt or other gamma functions goes to inf at x = 0, but if you look at the actual slope of a discrete 1/255 step it's just very steep.

(b/d) of 1.0 to 1.5 is best. At 1.0 you never get white until infinite intensity which is not ideal (you can see that in the basic rational exposure modes of floatdd). Something above 1.0 means you hit white somewhere sooner (you can work out for what x exactly you hit white and formulate it that way if you want). Hitting white somewhere around x = 3 or 4 feels good to me.

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