It seems with some QuickTime codecs, the gamma is slightly changed by the QuickTime framewok when frames are decoded. This is a known problem when using QuickTime.
easyDCP Creator allows to compensate this QuickTime-Gamma-Shift. By default, a value of 2.2 is set for gamma of the input color space. You can add additional color space transformations or adapt existing transformation settings.
To do this, please follow this steps:
- Open the folder containing the color transformations by right click on a Picture Track File -> "Color Processing" -> "Open Color Transformation Repository...“.
- Duplicate the standard XML-File for RGB -> XYZ color transformation "color_transformation_itu709_to_xyz.xml" and rename it for example to "color_transformation_itu709_to_xyz_quicktime_fix.xml"
- Open the new file with an editor and change the title:
Edit the "name"-attribute in "transformation"-Node, for example "ITU 709 -> X'Y'Z'" in "ITU 709 -> X'Y'Z' (QuickTime AppleProRes)
- Change the source „gamma“ from 2,2 for example to 1,6*. Unfortunately we cannot give information which gamma value fits to which codec since the certain value depends on some additional factors (used operating system /variant and version of specific codec and so on)
- Save the changes and restart easyDCP Creator
Now you can find the adapted color transformation as new option by navigating to Picture Track File -> "Color Processing".
Alternative solutions to prevent from Gammashift:
– Use an user defined sRGB to XYZ 3D-LUT compensating the corresponding Gammashift for the used codec.<
– Increase the gamma oft he Mov file´s gamma before you ingest it into easyDCP Creator.
– Use DPX or TIFF still image picture sequences instead of QickTime video.