Why is the brightness of my iMac become 100% automatically when I turn on..

Question

Why is the brightness of my iMac become 100% automatically when I turn on my computer even though I set the brightness to the lowest before I shut it down.
I want to set the brightness to the lowest every time I turn on the computer automatically.
Is there anything I can do?

Answer 1

Hi,
There seems to be a serious issue with screen brightness on the 24" iMac. About 6 days ago I bought a 24" iMac (2.66 Mhz model w/4 GB RAM + 640HD).
Out of the box it had Leopard 10.5.5 installed; there were several problems.
1. Screen brightness was way too BRIGHT. Display preferences would not pull brightness down. At least not down far enough so that the screen could be viewed without extreme discomfort. Plus add insult to injury a reboot would reset the preferences to maximum brightness. NOTE: An upgrade to 10.6.1 did NOT fix the issue.
2. Viewing a browser page via either Safari or Firefox (latest versions of each) was not good. A vertical scrolling would be jumpy and appear pixelated. Upgrade to 10.6.1 seemed to fix most of the issue in Safari, but Firefox was still not working properly. The issue appeared like a horizontal "ripple" in about the bottom 2/3 of the browser window. The effect did NOT extend outside of browser window. Changing screen resolutions did not work.
3. Connecting a USB Logitech head set caused issues with Sound preferences.
If the head set was connected during startup the machine would recognize them as main sound. The internals speakers did NOT appear in the Sound preferences. as an optional choice. Removing USB headset and reboot would return the internal speakers to the Sound preferences. Plugging in headseat would work for a while. We could repeat and same problem would occur.
These are all in 10.6.1 - definate bugs.
Returned with the iMac to the Apple store. Bottom line, after nearly three hours; the Apple technician, and everyone could see what we were talking about.
Regarding the screen brightness. Nothing they could do about it. They stated that "not too many people have complained about it, to their knowledge." They stated that the electronics in the "florescent" panel could not be turned down the same way. TRANSLATION: The programers at Apple let this one slip past them. As a customer (software programmer & network analyst) I expected a bit more of an intelligent answer.
However.
Examining the 20" model I noticed that we could turn down the screen brightness - at least to a level that my wife and I could live with. PLUS the settings remained after a restart. Something that was NOT happening with the 24" model.
So - we exchanged the 24" for a 20". Frankly we are a LOT happier. The Safari/Firefox issue is still carried over to the 20". However it is not nearly so noticable on the smaller screen.
Plus the USB headset did not cause the same Sound Preference issues.
So - Thanks for the speedy return/exchange of the iMac. But someone needs to look at this from the programming side of things.