broght new iphone 14 pro max screen issue

Hey there AndrewRyu,

Thanks for reaching out to the Apple Support Communities. Just to confirm, is the brightness decreasing on its own while in low light? If so, this may be expected behavior if you have auto-brightness enabled in Settings > Accessibility > Display & Text Size.

For more details on how to disable auto-brightness, and how to manually adjust the brightness and color temperature on your iPhone for the best look, check out this link here: Adjust the brightness and color temperature on your iPhone, iPad, or iPod touch - Apple Support

Adjust brightness in Control Center

You can quickly adjust brightness in Control Center on your iPhone or iPad:

1. On an iPhone X or later, or an iPad with iOS 12 or iPadOS, swipe down from the top-right corner of your display. On an iPhone 8 or earlier, or on an iPod touch, swipe up from the bottom edge of your display.

2. Drag the brightness bar  up or down to adjust the brightness.

Learn more about the display on iPhone X and later.

Adjust brightness and color temperature in Settings

1. Go to Settings > Display & Brightness. 

2. Drag the slider to the right or left to adjust the brightness.

From here, you can turn on Dark Mode, which is designed to make the screen easier on your eyes. Dark Mode uses a dark color scheme that works system wide, including with the apps that come with your device and with many third-party apps.

True Tone, which is on by default, uses advanced sensors to adjust the color and intensity of your display to match the ambient light, so that images appear more natural.

If you turn off True Tone, the display keeps color and intensity constant, regardless of changes in the ambient light.

You can also turn on Night Shift, which adjusts the colors of your display to the warmer end of the spectrum—making the display easier on your eyes. To adjust the color temperature to be warmer or colder, go to Settings > Display & Brightness > Night Shift and use the color-temperature slider.

About brightness levels

iOS devices use an ambient light sensor to adjust brightness levels based on the light conditions around you. The sensor lowers brightness in dark locations and raises brightness in light locations. The auto-brightness feature is on by default.

When auto-brightness is on, you'll notice that the brightness slider on your device moves according to changing light conditions.

You can turn auto-brightness on or off in Settings > Accessibility > Display & Text Size. To reset the auto-brightness settings, turn off auto-brightness and then turn it back on. 

Let us know if that's able to help.

Cheers!