I have a 4k clip in after effects, in which I have used the Keylight effect. The shot looks like this (I have to blur the face for privacy reasons): enter image description here

Anyway, but in some frames, towards the end of the video, the shot flashes briefly to this and back to the original: enter image description here

This sometimes happens during preview while I am working if I start running out of RAM, but I don't know for sure. Sometimes, the shot stays green like that for quite a while before switching back.

I have had this happen in other after effects projects that were not 4k...

I don't know what is going on. Can someone please tell me how to fix this?

  • Dose same thing happen, when you export your video? Most probably it is just "preview" thing, because your system can't handle KeyLight for 4K in realtime. Try to flush your media cache, it can help, is preview was rendered wrongly
    – Shultc
    Commented Aug 24, 2018 at 10:30
  • @Shultc It happens a lot in the preview, but, for the first time, I had it happen after I rendered as well.
    – skillz21
    Commented Aug 24, 2018 at 10:31
  • Is it just one single frame or more than one frame when you render?
    – Capogear
    Commented Oct 17, 2018 at 11:19
  • @Capogear I solved the issue! I have already written an answer down below, thanks for taking your time to check out my problem :)
    – skillz21
    Commented Oct 30, 2018 at 10:44

3 Answers 3


This happens to me sometimes using Keylight. I find that if I make a tiny adjustment to the settings (holding down CMD and dragging on one of the controls (eg Screen Gain or Screen Balance), it usually disappears.


When Keylight acts that way, usually emptying the cache helps. If it doesn't help, just add a new adjustment layer to force everything render again.


I fixed this issue by changing the renderer from OpenGL to Software based. The problem is still there when previewing in the timeline, but it's gone after exporting.

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