How do i adjust brightness for 24 inch LED Cinema Display?

[nawoo]

Alright i turned down the brightness last night to half. Unplugged my macbook pro and took it somewhere else.

Plugged it back in the morning, the LED powers up at half brightness. But Lo and Behold, i can't adjust brightness anymore.
The f1 and f2 keys don't work!! All other keys on my apple wireless keyboard work.

I go into Displays under System preferences. The only option to adjust the brightness shows as Color LCD, which is for my MBP.

Under LED Cinema Display, There is no slider to adjust brightness!! The Apple LED cinema display guide says to either press the f1 & f2 keys, or go into System Preferences and use the slider. But WTF, where the hell is the slider.

I've already tried using different arrangements. I've always set my LED display as the primary display, and have always been able to adjust my brightness.

WHy can't i do anything now??? I'm sitting here with a very dim 24 inch monitor

 

[alphaod]

Have you tried restarting your computer with the display plugged in?

 

[thecreativ1]

Bump. This is a problem for a lot of people. Apple's support discussions page has lots of threads on this, with no fix that I've seen yet. It seems to have something to do with how the external displays interact with the Intel GMA950 graphics. I have this same "no brightness slider" bug with a Mac Mini C2D and a 20" Cinema Display.

 

[superscientific]

I know this sounds crazy but is your display USB plugged into the computer? Without that it will not be able to control your display settings. I did the same thing with my Mac Pro at first and was getting so frustrated. But then I realized that my USB from the display was not plugged in. I plugged it in and BAM! There came my display slider and the keys for brightness worked again. If it is plugged in then sorry, I just thought I would post just incase people were not plugging the USB in. This is on the new 24" LED Cinema Display.

 

[nawoo]

yup, the USB needs to be plugged in before the slider can show up.
Works everytime now

 

[bridgeandtunnel]

Thank you for the usb tip. !!!!!!!!!!!

 

[Fabjanx]

Thank you for the usb tip. !!!!!!!!!!!

If its not working with the USB plugged in you can also try another USB port. After endless googling and resetting every type of RAM in the computer this did the trick for me. Just try another USB port.

 

[cosmichobo]

Just to add to the thank-you's - THANK YOU!

First port of call - Apple's website - just made it sound as though my "older" 24" Cinema Display could no longer have its brightness adjusted..! I'm glad I kept looking.

Not sure when I unplugged the USB cable - I know I have used the screen as a USB hub in the past... but it was unplugged, and the brightness was really starting to bug me.

 

[nigelstone1]

Easyontheeyes from the app store works if you aren't a complete control freak about the degree of brightness. It's not the same shade of 100% sliding and more like a 5 stage of brightness which controls both screens, but that's better than nothing and you don't need to use an extra port on your machine.

The icon installs top right of screen by dropbox, bluetooth, wireless icons.

 

[TheAshMan]

Good tip. I encountered the brightness slider missing issue as well, adding a LED Cinema Display 24" to my 2019 MacBook Pro 15" as a 2nd monitor. The first monitor is an LED Cinema Display 27". Connecting the USB to the 24" display brought forth the display brightness slider, but it didn't work. After a restart, with all connected, it worked like a champ. Disconnected USB afterwards and all still works fine.