GH4 video judder/strobing - a solution

Edgar F wrote:

Thank you for your reply. I'll try to interpret 30p footage to 24p and see if judder. If I understood correctly the strange effect you can even see on moving subjects on still shots is judder due to LCD frequency, correct?

...yes, you need a cinema 24fps TV - usually they run at 120Hz, 120 / 24 = 5, the LCD displays the first frame 5 times, then displays the next frame 5 times, etc.

most LCD TV's and monitors (desktop, laptop, the rear GH4 monitor etc), run at 30hz, or maybe 60Hz.

60 / 24 = 2.5

30 / 24 = 1.25

so in the case of 30Hz LCDs, to display 24fps, the first few frames are shown as you'd expect - once each, then the next frame is shown twice (which freezes motion), then the next few frames are shown once as you'd expect - once each, then the next frame is shown twice (which freezes motion), etc, this is the judder you are probably seeing.

google '3:2 pulldown'.

Most new TV's that don't use 120Hz do have motion compensation, for playing 24fps blu-rays, but most other monitors, particularly the rear monitor of the GH4, will judder - this is a display issue not an issue with the actual footage recorded.  Yes a real shame panasonic couldn't use a 24 / 25fps compatible monitor!

If you see juddery footage, pause the footage, and move ahead one frame at a time, movement will progress in even steps, with no sudden jumps, it's only when played at normal speed does the display issue occur.

Also use a shutter angle of 180 degrees or 240 degrees, this will introduce the 'right' amount of blur to moving objects and help keep pans as smooth a possible.

Here in the UK, TV is still recorded and broadcast at 25fps, from the days of TVs running at 50Hz -the same as our AC mains power.  Film taken at 24fps, was actually speeded up slightly when broadcast, this avoided any nasty frame doubling or dropping - so avoiding judder.  It's been a constant problem, you just have to learn how to work within the requirements you wish to deliver to, for me it's broadcast 25fps, and the limitations of display equipment.