Check out this video of Mavis Co-Founder, Dr Phil, as he dives into the Monitor Tools (including Focus Peaking) inside Mavis Camera:
The focus peaking visualisation is a tool to assist with focusing. Contrasted edges within the viewfinder image are highlighted a bright colour to make it easier for you to determine which part of your scene is in focus. The more highlighted edges you see, the more likely it is that that part of the scene is in focus.
Focus Peaking has additional options which can be accessed by tap and holding down the focus peaking icon within the monitor toolbar. This can also be set within Settings > Viewfinder > Focus peaking menu.
Both the intensity of the highlighted area, and the colour can be adjusted.
Tip: The best way to check focus using focus peaking is to follow the points below:
1. Drag the focus control in a direction that makes the subject become sharp and focused. With focus peaking switched on you should see lots of highlights as the sharpness increases.
2. Continue to drag the control in the same direction until subject become slightly blurry and the highlights reduce. This will give you an opportunity to see the point at which most highlights are visible.
3. Drag the focus control back to the point where the most highlighted edges could be seen. Your subject should now be sharp and focused.