[Sidefx-houdini-list] Linear Workflow
edward at sidefx.com
Thu Aug 26 14:39:49 EDT 2010
On 8/26/2010 3:45 AM, Andy Nicholas wrote:
> What also didn't help my understanding was by putting Houdini's
> colour correction gamma setting to 1/2.2 it made a pure linear ramp
> (defined by a shader) in Houdini look correct in the render (i.e. an
> even distribution of black through white), but using a value of 2.2
> made it look anything but linear and over exposed the dark areas.
You're missing the fact that the eye itself also has a nonlinear
response. When you put in a 2.2 value into mplay, you're now undoing the
power curve that the monitor applied, giving you linear _luminance_. Do
not confuse this with _perceptual_ lightness.
If you want *perceptual* (lightness) linearity, then you need to
generate an approx. 0.4 power luminance curve , explaining why
putting an mplay gamma value of around 0.4 "works".
Lastly, this issue has nothing to do with Houdini in particular. Take a
linear gradient in another package (say Photoshop) and you will see the
More information about the Sidefx-houdini-list