PLogLin node

This documentation is for version 1.0 of PLogLin (net.sf.openfx.PLogLin).

Description

Convert between logarithmic and linear encoding.

This method uses the so-called “Josh Pines log conversion” or “printing density transform” (as described in http://lists.gnu.org/archive/html/openexr-devel/2005-03/msg00006.html), which is based on a single gray point, rather than the white and black points in the Cineon formula (as implemented in the Log2Lin plugin).

Log to Lin conversion: xLin = linRef * pow( 10.0, (xLog * 1023. - logRef)*density/nGamma )

Lin to Log conversion: xLog = (logRef + log10(max( xLin, 1e-10 ) / linRef)*nGamma/density) / 1023.

Inputs

Input	Description	Optional
Source		No
Mask		Yes

Controls

Parameter / script name	Type	Default	Function
Operation / operation	Choice	Log to Lin	The operation to perform. Log to Lin (log2lin): Convert the input from logarithmic to linear colorspace (usually after a Read node). Lin to Log (lin2log): Convert the input from linear to logarithmic colorspace (usually before a Write node).
Linear Reference / linRef	Color	r: 0.18 g: 0.18 b: 0.18	Linear value of the reference gray point. Set this to the linear value that corresponds with the log reference value.
Log Reference / logRef	Color	r: 445 g: 445 b: 445	Log value of the reference gray point. Set this to the log value that corresponds with the lin reference value.
Negative Gamma / nGamma	Color	r: 0.6 g: 0.6 b: 0.6	The film response gamma value.
Density / density	Color	r: 0.002 g: 0.002 b: 0.002	Density per code value. The change in the negative gamma for each log space code value. This is usually left to the default value of 0.002.
(Un)premult / premult	Boolean	Off	Divide the image by the alpha channel before processing, and re-multiply it afterwards. Use if the input images are premultiplied.
Invert Mask / maskInvert	Boolean	Off	When checked, the effect is fully applied where the mask is 0.
Mix / mix	Double	1	Mix factor between the original and the transformed image.