A simple cross dissolve, OK? The rushes are captured from a Sony DVcam. Using either two seperate captured files, or one file cut in the middle, one is dragged into the video 2 timeline, it matters not which.
Then I drag the X-dissolve effect and render. The luminance during the transition is ALWAYS too low, looks like the chroma too.
I haven't as yet looked at the difference on a waveform monitor to measure it, but it is quite clear to the naked eye.

I remember reading that someone had come across the same problem but can't find the post again