When doing average/min/max luminance calculations for tonemapping, ignore pixels that are outside of the strip rectangle. Due to how VSE innards work, when a strip is positioned to not cover the whole screen, "the rest" is filled with transparent black. For tonemapping, this was dragging average calculated luminance way down. Images of the issue in PR. Pull Request: https://projects.blender.org/blender/blender/pulls/127207