Premiere Pro CC 2018
I was baffled,
Not understanding why my dissolve transitions in a new Premiere project are not linear, and too lift too fast,
I validated this in the Lumetri Scopes window.
In an older project, at 50 percent transition duration, white color is at 50 percent intensity like you’d expect from a linear transition.
But in my new project, at 50 percent transition duration, white color is at about 75 + percent intensity as if it’s gamma corrected.
After some web research in discussion groups, I found that the option that doe’s that is:
Sequence Settings > Composite in Linear Color
And unchecking it solves the problem.
It’s still weird to me that Composite in Linear Color breaks the linearity of the dissolve transition,
But at least there is a solution.
Along with the Filtering Type, and the File Path attributes,
The File Attributes for texture nodes in Maya have the option to set a Color-Space with which to interpret the color values stored in the file’s pixels.
For example, JPG and PNG files will be interpreted as sRGB Color-Space by default, which means the color values will be ‘linearized’ (their Gamma Correction will be removed), and EXR or HDR files will be automatically interpreted as ‘Raw’ (linear) Color Space.
When an sRGB file like a PNG is intended to serve as linear data, and not as image display. it’s sometimes needed to set its Colors Space attribute to Raw. this is usually the case with Bump maps and Normal maps.
Equivalent setting are also found in other 3D software, see Blender Texture Color Space.
When loading texture files into a Cycles Image Texture node, it’s a good idea to take a moment to set the Color Space parameter correctly.
This parameter sets how the color data is intended to be used in the shader, that is, if it will be used as ‘Color’ like a Diffuse texture for example, or as ‘Non-Color Data’ like a Normal map texture example.
The reason behind this is that texture data encoded in sRGB color space (JPG, PNG,..) intended to be used as color should be ‘linearized’, that means the gamma correction sRGB files are automatically encoded with should be removed, so the the color data will represent linear color values suitable for the processing of shaders and compositing the final rendered image*,
While texture data intended to be used as data like height or direction or percentage, shouldn’t be linearized, assuming that the colors were saved without adding a gamma corrections to them.
A common example of that is when using a normal map stored in PNG format,
When the Color Space parameter is set to ‘Color’ the resulting bump normal might look wrong, and also display hard edges along UV coordinates seams.
Setting the Color Space to ‘Non-Color Data’ will solve the problem and interpret the bump normals correctly.
> usage of a texture as input for a non-color parameter like displacement will automatically use it as linear color.
> 32 bit float formats like exr are automatically interpreted as linear color by the renderer (the viewport material display will still show a differance so it’s better to set it to ‘Non-Color Data’ anyway).
> It should also be noted that Blender has two parameters controlling the interpretation of an image file one in the Image Texture Node that controls the color usage, one in the Node properties that controls how the file format is interpreted,
And also general color management settings that control the display of colors and saving of image files.
> It should also by noted that I’m still baffled by Blender / Cycles color management.. 🙂
* Linear color is also suitable for post rendering / post production compositing for image development and VFX.