# PLogLin node¶

*This documentation is for version 1.0 of 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. |