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mister3d
03-11-2010, 11:51 AM
What's the practical difference between the two modes? Am I right the maximum cuts off based on background luminance more abruptly, whereas screen does it based on the inverse multiplication, therefore the transition is more gradual?

Aneks
03-11-2010, 03:32 PM
screen is :

1-[(1-A)x(1-B)]

max or maximum will just return the brightest pixel.

Screen can be problematic when comping in Linear float as it can easily lead to negative values. It is designed to emulate the look of double exposure on negative film. as it essential an invert a mult and then another invert.

I would rarely find a need for screen, much more likely to use an add (in linear space). I use max all the time for mattes and hair and all kinds of stuff.

mister3d
03-11-2010, 04:25 PM
screen is :

1-[(1-A)x(1-B)]

max or maximum will just return the brightest pixel.

Screen can be problematic when comping in Linear float as it can easily lead to negative values. It is designed to emulate the look of double exposure on negative film. as it essential an invert a mult and then another invert.

I would rarely find a need for screen, much more likely to use an add (in linear space). I use max all the time for mattes and hair and all kinds of stuff.
Thank you for the reply. I understand the screen math (less of max, though I understand it uses "if" brighter, "then" the values are used).
I'm not yet familiar with negative values problem, I also read the subtraction can lead to them in floating-point format. I'm not sure why.

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03-11-2010, 04:25 PM
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