Weird artifact in part of image

[FrédéricChabot]

hi folks! New here, aspiring low key cinematographer..

im shooting a video for an art gallery. Im having weird artifacts in some places.. in the video linked you can see it after the first scene.

https://youtu.be/od3iGEUkN38 

im shooting with a a6500 in slog3 with ibis on, could the ibis be a problem? Looking at the raw footage its looking ok.. i noticed it in premiere after a couple of exports.. 

[FrédéricChabot]

I though maybe i exported too many times, if there is such a thing? Like 30 times..

[Steve Griffiths · Accepted solution]

The number of exports you do will have no affect - so don't worry about that.

A quick look at your video - if I'm seeing what you are seeing it looks like you may have slowed that shot down and maybe used 'optical flow' as your slow motion choice? If that is the case what you are seeing is optical flow failing to correctly track the pixels in the white areas of the frame. Mainly because there's very low contrast  between the variations of 'white' on the wall.

If you are NOT slowing that shot, I don't know what it is, sorry.

[FrédéricChabot]

right! i forgot about that, i did use optical flow!

i will try something else then!

thx so much!