Flickering on iMac Retina 5k display


I just bought an  iMac (Retina 5K, 27-inch, Late 2015)

processor 3.2 GHz intel core i5

memory 8GB 1867 Mhz DDR3

graphics AMD radeon r9 M390 2048 MB

I've been using hit film on a Mac book pro, I wanted something FASTER ;)

I installed hitfilm Pro 2017 on my iMac,  and I started working on a project. after 10min, the full screen start to be the screen start to be flickering, 

I don't know how to explain but here is the link to see the problem  :


I took it back to the store, they tested it and they said there is no problem with the iMac, it must be from a software...hitfilm is the only software installed. I reinstalled it again, and it starts to do the same things ! 


please help... thank you ! ben. 



  • @jacquierbengmailcom if you close HitFilm and play back the same video using QuickTime (I think that's what you are doing in this video?), does it do the same thing?

  • when i close hitfilm it does the same thing for a min and then it stop. to completly stop the flickering i had to uninstall hitfilm. i tried hitfilm pro 2017, hitfilm 4 as well... i tried After effect trial version and it works perfectly... so the problem is definitly hitfilm..i have no clue what's going on ..

  • Maybe you could try moving the app bundle out of /Applications, say on your Desktop for example and try playing back the video in QuickTime then?

    What happens if you restart your computer and play the video (without opening HitFilm)?

  • i have no problem with any videos or quick time if hitfilm is not running, it happens only when i work on hitfilm. it starts doing it after few minutes.

  • is this orginal-clip with variable bitrate?

    when you download a youtube-film and import in hitfilm, the flickering done?

    play the orginal-clip or the hitfilm-exporting-clip with vlc for mac, its the same?


  • edited June 2017

    yeah right i only tried with videos coming from my dslr canon 7d mark ii, can it be cause by the camera? i'm gonna try with a video from youtube, thank you i ll let you know ! 

  • If the problem only manifests after 10 minutes then it may be heat related. Are the fans running loudly?  Please check that your machine is well ventilated.

  • hey thank you for answer. when i had the problem the first time i took it back to the store, they tested  everything, apparently the imac is all good, so i don't think it's a heat problem but i'm gonna check, how do i do that? 

  • Aladdin4dAladdin4d Moderator

    @jacquierbengmail.com First thing is make sure vents aren't being blocked by anything but from your video it looks like you don't have anything in the way and I think the store would have at least checked the vents to make sure they are clean.

    To really check for heat related problems you need to stress test things. Luckily there are some benchmark programs that make it easy. The free part of Geekbench 4 should let you test the CPU. GPUTest is available for Mac and so is Cinebench. Both will put your GPU through its paces. There's a free trial for TG Pro which you can use to monitor temps while the benchmarks run. I know the store said your system is ok and it might very well be but what your video shows looks very much like an overheating GPU problem. 

  • Does it flicker at different resolutions? 

    You might want to visit discussions.apple.com There are many threads pertaining to this topic

  • hello! i couldn't reaolve the problem. i changed for a PC.

    thank you all fir your help!

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