That would be the automatic feature that helps save power, or your electricity went out.
Don't spend too much time using it at once. Get a screen guard to darken it. Here is another suggestion. If you get a headache from the computer screen it is likely you are photosensitive, i.e., more sensitive to light than the average person. The average computer's built in controls will not darken the screen enough for you to avoid headaches. SHADES is an excellent tool that you can download to add greater control to darken the screen. See related link.
Selective pressure is evolutionary pressure.The animals evolved due to selective pressure.Selective pressure caused the color to darken.
The noun forms for the verb to darken are darkener and the gerund, darkening.
Some glaucoma medicines will darken the iris color.
You can darken your hair using the Black Ice spray, or the natural remedies such as herbs sage and rosemary.
And She Would Darken the Memory was created on 2007-07-16.
How do you darken or embold text in a scanned PDF document?
lighten
darken
darken
No
if you mean without tanning or false tanning, there is no other way to darken your skin