can a LED-backlit laptop screen generates a true black?

[ardv]

LED-backlit laptop screens uses LEDs for backlighting
so if a have a black picture, can this monitor turn off the LEDs behind that picture? so as i get a real dark?
and is there any software in linux that let me controll the LED backlit of the screen?

[xenopeek]

Look up the specs for your screen. Almost certainly you have an edge lit screen, where there is one or several strips of leds under the edge of the screen that provide the backlight for it — so it has one brightness setting for the entire screen and you can't individually dim pixels or areas of the screen. And if you turn the backlight off, no light comes out of the screen so it will just be completely black. You can't see pixels that don't have light behind them.

Good HDR screens have zones that are individually backlit so they can have different backlight intensity. One zone can have its backlight turned off to make it truly black. You will already know if your laptop has this, because you will have paid through the nose for it and you'll have drowned in all the included stickers and marketing material about how good the HDR on this laptop is. And probably the laptop has RGB lighting on the keyboard and everywhere, because this is mostly the domain for overpriced gaming laptops.

What's recently becoming available are laptops with OLED screens. OLED screens are not backlight and can be truly black on any pixel. If you've got a couple of thousand to burn you could look into that. They are expensive but those are the best screens for color accuracy.

For a screen that is edge lit the technology simply does not provide for what you want. The only thing you can do is control the brightness of the entire screen.

[ardv]

Look up the specs for your screen. Almost certainly you have an edge lit screen, where there is one or several strips of leds under the edge of the screen that provide the backlight for it — so it has one brightness setting for the entire screen and you can't individually dim pixels or areas of the screen. And if you turn the backlight off, no light comes out of the screen so it will just be completely black. You can't see pixels that don't have light behind them.

Good HDR screens have zones that are individually backlit so they can have different backlight intensity. One zone can have its backlight turned off to make it truly black. You will already know if your laptop has this, because you will have paid through the nose for it and you'll have drowned in all the included stickers and marketing material about how good the HDR on this laptop is. And probably the laptop has RGB lighting on the keyboard and everywhere, because this is mostly the domain for overpriced gaming laptops.

What's recently becoming available are laptops with OLED screens. OLED screens are not backlight and can be truly black on any pixel. If you've got a couple of thousand to burn you could look into that. They are expensive but those are the best screens for color accuracy.

For a screen that is edge lit the technology simply does not provide for what you want. The only thing you can do is control the brightness of the entire screen.

thank you.
my main purpose is not the quality of colour but the eye safety, i oftenlly get hurts in my eyes when using the laptop.

[xenopeek]

Decrease the brightness setting for the screen. There is probably a key for that on your laptop. Usually you have to hold the Fn key and press on the function or digit keys that also has a decrease brightness icon on it.