Dim screen isn't always a fault — sometimes just Eco Mode enabled. If settings are right and issue persists, backlight is weakening.
See if any of these signs match your device — each one increases the likelihood of this fault.
These are the causes we encounter while repairing Dim screen — ranked from most to least common.
Eco Mode or Energy Saving enabled
Backlight LEDs weakening from heavy use
Local Dimming set to High dimming zones
Faulty ambient light sensor
Backlight driver delivering low voltage
OLED pixel aging (for OLEDs after years)
Any of the following = a danger signal — call now and don't try to fix it yourself.
On-site diagnosis, clear pricing before any work, and a documented 6-month warranty.