How can I fix my emachine d620 the screen has gone very dark

[Edel__]

My laptop screen has gone very dim???

 

[Saga Lout]

Is it only doing this on battery or with the mains power connected as well?

Does it have two Function keys, one with a moon and the other a sun? If so, press the Sun one to brighten things up. If that doesnt work, try it again while holding down the Fn key to the left of your spacebar.