Max Shutter speed
Panasonic GX850 can shoot continuously at max speed of
10.0 fps and has max shutter speed of
1/500 sec. GX850 also has an electronic shutter which can shoot silently at max speed of
1/16000s. One thing to keep in mind is that electronic shutter may cause rolling shutter / jello effects, and also banding issues under artificial light on your images.
Flash
Unfortunately GX850 doesn't have an external flash shoe so you are limited with the built-in flash.
Focusing
Panasonic GX850 features a Contrast Detection autofocusing system. The AF system has 49 points to choose from. Panasonic GX850 also features
Face detection AF where it intelligently detects the faces in the frame and locks the focus automatically.
Focus Stacking
Macro shooters will love Panasonic GX850's Focus Stacking feature. In this mode, GX850 automatically composites multiple shots taken at different focal positions using focus bracketing to create a single image with maximum depth of field.
Post Focus
Panasonic GX850 has a special Post Focus mode which uses its 4K video and focus bracketing features together to shoot and stack a burst of images into a single image which you can change the focus point on the LCD screen after it is taken.