Key Facts

• The camera live view is one frame behind due to the image processing pipeline, faster refresh rates reduce delays
• HDMI latency does not depend on cable length
• Most monitors have low latency
• HDMI can carry audio and video and those need to be synchronised: if one of them is slower than the other a delay is introduced to match up
• Resolution plays a role but not as important as others

GH5M2 and GH6 Lag between LCD and HDMI

• The camera LCD has a resolution of 960×640 pixels and a refresh rate of 60 fps that can be reduced to 30 fps
• When recording the camera shows the live view on the LCD with a delay of c 1 frame from real life
• If you go into the menu HDMI Recording Output and set Sound Output  OFF you can see the real lag between the LCD and the HDMI
• This lag is typically 2 frames from the LCD 
• As frame  rate drops the lag increases
• When the Sound is disabled the lag of the GH6 is generally better than the GH5M2

Video Tutorial with my recommended settings

Items shown in this video

1. Atomos Shinobi: https://amzn.to/35DmFhD

2. Manfrotto 290 Xtra: https://amzn.to/3sSYggF

3. Manfrotto Light video head: https://amzn.to/3vTCHPc

4. Smallrig Monitor Mount: https://amzn.to/367f22z

5. Smallrig HDMI cable: https://amzn.to/3sVwNe9

6. Panasonic GH6: https://amzn.to/3HTUZlv

7. Panasonic 10-25mm 1.7: https://amzn.to/3KtxAcn

8. Atomos Ninja V: https://amzn.to/3MEKia0

HDMI Optimisation Wrap Up

• Monitoring has acceptable delays from live time 50-150ms
• Audio recording introduces a delay of 65ms on the GH5M2 and 35mm on the GH6 
• The GH5M2 lag  of 190ms in 24p is too high and should be reduced to 160ms
• There is a bug in the 30p mode on the GH6 as the lag is higher than 24p this needs to be corrected