Max brightness should only be used for 10 minutes at most to protect the battery; plus, I found the light gets too hot to hold if it's on Turbo for any longer. Though it performed well ...

The brightness control buttons look like a light bulb, sun ... You can click on the system tray’s Wi-Fi, battery, or volume icon or press Win+A to open the Quick Settings panel.

This can be due to Auto-Brightness – a feature that adjusts your screen's brightness based on how much light is around you ... finger up and down on the sun icon. Why does my iPhone screen ...