Cannot adjust brightness in windows 8

Update Device Drivers

Try this:
https://forums.lenovo.com/t5/Lenovo-P-Y-and-Z-series/Z400-Adjusting-the-Brightness-in-Windows-8-1/ta-p/1303113

If you can't go further down your probably at your lowest brightness level

Read at http://support.dell.com/support/edocs/SYSTEMS/ins4150/en/i4150_om.pdf

laptop ot desktop monitor ?

Adjust your monitor's brightness and contrast

You can adjust the brightness and contrast of your monitor to improve the readability of text and to make digital pictures appear more like they'll look when printed.

To improve the results when adjusting the brightness and contrast settings for your display, use Display Color Calibration. (Display Color Calibration helps you adjust these color settings and others.)

The way you adjust brightness and contrast varies and depends on your specific display.

Brightness and contrast buttons on the front of the monitor.

Some monitors have brightness and contrast controls on the front and use the standard symbols shown in the following image.

Brightness and contrast symbols

On-screen menu. You can change the brightness and contrast settings for some displays by using an on-screen menu, and then setting the brightness and contrast in the resulting menu. Many times, you can view the on-screen menu by pressing a button-possibly labeled Menu-on the front of the monitor.

Laptop display. Laptop displays don't have brightness or contrast buttons on the front.

For a majority of laptops, there isn't a control for setting the contrast.

However, you can set the brightness of many laptops by pressing and holding the Fn key, and then pressing a function key to decrease brightness ( ) or increase brightness ( ).

http://windows.microsoft.com/en-US/windows7/Calibrate-your-display#

When using Display Color Calibration on a laptop, set the display to the maximum brightness setting.

Adjusting brightness automatically using adaptive brightness

Adaptive brightness is a feature in Windows that uses a light sensor to automatically adjust the display brightness to match the lighting conditions in your computer's surroundings.

To use adaptive brightness, you must have light sensors installed and enabled on your computer.

To determine if your laptop or computer monitor supports adaptive brightness, look for the Enable adaptive brightness setting in Power Options (mentioned in the following procedure) or check the information that came with your computer.

To turn adaptive brightness on or off

Open Power Options by clicking the Start button , clicking Control Panel, clicking System and Security, and then clicking Power Options.

Under any plan, click Change plan settings.

Click Change advanced power settings.

In the list, expand Display, and then expand Enable adaptive brightness.

To turn adaptive brightness on or off when your computer is running on battery power, click On battery, and then, in the list, click On or Off.

To turn adaptive brightness on or off when your computer is plugged into an outlet, click Plugged in, and then, in the list, click On or Off.

Click Apply. Click OK.

hope this helps

To adjust the brightness you press the Fn key on keyboard and simultaneously press F10 to reduce brightness. Press Fn simultaneously with F11 to increase brightness.

Ensure you have the correct drivers installed and using Fn and F7 plus looking at the Power settings, Adjust Brightness settings adjust as you require.

Actually, the problem isn't with the drivers. Right click on the battery icon in your system tray. Select "Power Options" (NOT Power4Gear eXtreme). On the right panel, select "Adjust the display brightness." Then, select "Change advanced power settings." Scroll down and open up the "Display" box. The options that are affecting your screen brightness on battery are "Allow SmartDimmer to reduce my brightness after," "Have SmartDimmer reduce my brightness by," and "SmartDimmer full-screen video mode." Playing with the percentages in these boxes will affect how your screen brightness adjusts itself. To get my screen to stop re-brightening itself, I changed "Allow SmartDimmer to reduce my brightness after/ On Battery:" to 100%. I then changed "Have SmartDimmer reduce my brightness by/ On battery:" to 0%. Finally, I set "SmartDimmer full-screen video mode/ On battery:" to Maximum Power Saving. This should solve your screen-rebrightening problems even with the 163.44 drivers (I use those too). Please Rate.
Thanks, Anand Fixya

windows 8 to 10 have the brightness control in the action center or power settings or look in the charms bar if your using windows 8 or 8.1 (note: if brightness doesnt change it maybe due to the OS not knowing how to change the brightness let me know if that ends up being the case)