All Windows Phone 8 powered Nokia Lumia smartphones are expected to receive the Lumia Cyan update, along with the Windows Phone 8.1 update, later this summer. The first devices to feature both updates include the Lumia 930, Lumia 630, and Lumia 635, giving us a first glimpse at a brightness slider that comes with the Cyan update.
As you can see from the image below, the brightness slider allows you to tweak your screen's brightness level to your specific liking. Currently, you can only adjust your brightness to low, medium, high, or automatic presets. This image is taken from the recently launched Lumia 630 - which runs Windows Phone 8.1 and Lumia Cyan.
You can take a look at the image below. Thanks for sending this in, everyone!