PLogLin node — Natron 2.5.0 documentation

# 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.