Automatic display brightness in iMac behaves wrong and is only semi-automatic

I use the automatic display brightness function in the System Preferences and I have noticed that it is doing totally wrong. When I turn the feature off and set the brightness to let‘s say maximum and turn the feature on again, the maximum will be used as the standard lighting. So when I set the maximum in a dark room, it will stay this bright. I tired it with 90 % brightness. When I open my windows to let light into the room, it goes up to 100 % and by closing the windows to a totally dark room it‘s going back to the 90 %. And sometimes when I set it to like 10 %, the iMac doesn‘t even react to my flash light. After a little time of tweaking around it works again.

I have restarted the iMac a couple of times, but it didn‘t help at all.

How can I fix that stupid behavior? My iPhone does fine. It uses the real ambient lighting.

What i did is to cover the sensor, set the brightness to as low as possible and activate automation. Putting the hand away set it to an optimal level. Is this how it‘s done?

– iMac Late 2015 27" (Mojave up-to-date, freshly installed a week ago)

– iPhone 8 Plus (iOS up-to-date)

Solution 1:

I found the solution: How to reset the System Management Controller (SMC) on your Mac

Simply turn the Mac off, pill the power chord for 15 seconds and connect and start it again. The brightness is now properly responding to the environment. I will better not touch the slider again.