I'm using Vegas Pro 23.0 Build 356 on Windows 10 Pro with a GTX3080.

When I drag and drop a video in and choose to set my project settings to be the same as the original, the video in the preview looks fine. My original video is from an Atmos Shogun using ProRes 422. When I do a straight export to a Sony XAVC S or even a AVC h264, I'll drag and drop the new rendered file back into my timeline directly under the original. When I mute the original, the rendered version is ~25% less bright than the original. Even if I drop it on the same event line, still less bright.

It's also less bright when I play it in a video player.

Trying a few different render settings give these results:

• AVC Blue-ray 1440-24p - OK (Matches what I see in the Preview)
• AVC Internet UHD 2160p - Dark
• HEVC Internet UHD 2160p NVENC - Dark
• HEVC Internet HD 1080p - OK
• Sony XAVC S Long 2160 FullColor - Dark
• Sony XAVC S Long 2160 Limited Color - Dark
• Sony XAVC S Long 1080 - Doesn't work - System out of memory error.
• ProRes 444 2160 - OK
• ProRes 422 LT 2160 - OK

What is going on with some of these render engines? Does it have to do with GPU involvement in the render?

Here's what I did next: I went into Options -> Preferences -> Video and turned off GPU acceleration of video processing. Then I restarted Vegas. And guess what? The video in the preview window is now dark like my rendered videos.

And then, there's another twist: If I go back to GPU acceleration of video processing, and then change my Preview from Full to Half, the brightness in the vides change. That happens with Draft, Preview, Good, and Best. I expect the resolution to change, not the Brightness in the video and the resolution.

Does anyone have any idea what's going on?

Thanks for your time and any suggestions or explanations.