Why is my monitor dimming all the time?

This may not be exactly your problem (since you have an external monitor) but under Lion on my laptop the screen brightness was adjusting to the ambient light. You can stop this by unchecking the box in the Displays System Preferences (under Display).

Hope that helps.

If you see it that way in 10.8, try to get royalities 😁.

I am having a similar issue, also with my new Mac Pro. I ahve (2) monitors connected- a new Samsung Syncmaster 2494 connected via the DVI port and a 3 year old Samsung Syncmaster2493hm connected to a minidisplayport with an active Accell DVI-D to Minidisplayport adapter. This is the monitor that occasionally dims. I had previously had a Mac DVI-Mini Displyport adaptor before the accell one and still saw the occasional random dimming.

.At first I thought that Apple built one into Lion just based on the weather/time zone/ip-address(geo position) but then it happened in the day time 🙂

That would be cool! And then they could add a remote "blackout" option that could wipeout the screen in case of theft, all from your iDevice of course 🙂

I have had my imac for about 1 year and all of a sudden mine is dimming also and I get it back by doing the same thing, clicking on "colour" in preferences. Why is it doing this right out of the blue? I'm thinking however that because my computer was getting so hot in the upper right hand corner at the back, that I may have changed the settings to sleep after inactivity. That would not cause this dimming however would it? I use smcFancontrol to control the heat now so it works great at keeping this thing cool but the dimming is driving me crazy.

Displays System Preferences (under Display), that John De Banzie suggested worked perfect for me. The only note is this option is only available for the actual MacBook display, and not for the external montior.

FYI, mine is a MacBook Pro 5.3 15" with a Samsung external SyncMaster2200 as the main monitor when plugged in.

Hi Guys,

This one got me at first too.

Their are TWO locations that effect the brightness of your monitor.

1) Preferences -> Displays -> Display (automatically adjust brightness) and

2) Preferences -> Energy Saver (automatically reduce brightness before display goes to sleep.

I'd recommend switching off the screen saver and going straight for 'Display Sleep' under Energy saver to preserve the screen and not to waste electricity.

A.

In my case, there was a setting on the monitor (also a Samsung) that solved the problem. On my monitor, there is a setting for 'MagicBright' that was set to 'Dynamic Contrast'. I changed it to one of the other settings and that solved my problem.