After 10.6.8 Mini Displayport to HDMI PROBLEM

Just tested with my 2009 iMac i7 with 11C73, and brightness DOES work. No question. So no idea why it's not working for you tom.davey.

Really? That's odd because the brightness control works perfectly for me in 10.7.2. Check your setup.

Grr. It may well be because I am using teleportd to control the iMac, but I'm not sure while it would make a difference. Obviously it does! So you guys all have two keyboard--one for your iMac and one for your mac using the iMac as a display?

*goes to eBay. begrudgingly buys an apple keyboard*

I use my existing Apple keyboard to control the brightness with my XBOX 360 or PS3 plugged into the iMac.

I've futzed with this for a while using a MBP and an iMac, both running 10.6.8. The problem is inconsistent for me, but seems to be linked to how long I've had the iMac on. If on chronically (as I usually leave it), the iMac tends not to respond to F1/F2 brightness keystrokes when I connect my MBP and use the iMac in target display mode. But if I reboot the iMac and then connect from my already running MBP, this restores brightness keystroke response. That is:

1) With MBP and iMac running, connect mini DP to start target display mode on iMac

2) If brightness keystrokes don't respond, disconnect mini DP and reboot iMac, leave MBP running

3) After booted to desktop on the iMac, reconnect mini DP - brightness keys should respond

This has worked consistently for me. Hope it works for you, too. Hope Apple fixes this permanently somehow soon, it sure is annoying.

Apparently I am late to the party but this is still not fixed...I am on 10.6.8. I have an mdp adapter for HDMI pluged into the iMac and the Ps3 and I can not go into Target Display mode.

Command F2 is not working. Display connector Status: No Display connected. But everything is pluged in!

I will say this, although Apple messed this one up, they broke functionality that wasn't broken in the first place but at this point since they did fix the same issue that was in Lion it's best to move on and upgrade to Lion. You have to face facts, Neither Microsoft or Apple or any other company for that matter is going to spend time and resources fixing small issues in their old software even if it's something they broke.

I moved onto Lion and love the system but not becuase of this issue but because I wanted some of Lion's new features. I certainly hope Apple realizes that this brightness control issue needs to be taken care of in SL but at this point I wouldn't bet on it and it's best to move on to Lion. Software developers and Apple are going to keep on giving their customers reasons to upgrade to Lion, it's inevitable.

DPJ there are those of us who can't switch to Lion because there are expensive and irreplaceable peripherals which will never get software past Snow Leopard. This issue has been going on since the release of 10.6.7 Apple has had quite a long time to deal with this and hasn't.

Any experiences with the new update (mountain lion 10.8)?

Does the brightness control works like in lion?

My experience of Mountain Lion is that something seems to be broken in the display port driver, or the default configuration on upgrade.

I have a 2011 Mac Mini Server with a Techlink iWires mini displayport HDMI cable (exclusive to Apple stores) bought at the same time. It worked flawlessly under Lion, but during then during the Mountain Lion upgrade the screen showed 'No Signal' and has not worked since (I will qualify that by saying that I performed the upgrade yesterday though).

The HDMI port on the Mac works fine, but I could really do with getting the much longer (5m) iWires cable to work.

A year later and this problem still persists. This is very discouraging. I bought a late 2011 MacBook Pro running Lion and plugged it into my 2010 iMac running 10.6.8 and BOOM! Eyes burning! Please Apple, help us!

OK, seriously? Just go buy Lion or Mountain Lion, and solve the issue. $30 is not worth a year of your life.

Can anyone confirm that Lion or Mountain Lion installed on the 27" iMac solves the problem? I can't get 36Joules solution to work, but occasionally stumble onto start/restart connect/disconnect combination that fixes the problem on my 10.6.8 iMac. When there's an automatic software update, the brightness controls ALWAYS start working again when it's in target display mode.

I've also found that there's some combination of Safe-Boot and start/restart that has works. Until it doesn't.

All said and done, I'd gladly upgrade the OS if that will solve it once and for all.

You can adjust it with utility in app store. I'm currently using macbook pro wich is connected to imac 27" through minidisplay cable. macbook lid is closed and I'm using 27" as external display. App is called "Brightness slider" and is available in app store. I downloaded it on MBP and now I can adjust brightness. Thanks god, because iMac almost killed my eyes!!

I have the same problem as well. Only just realised that all my problems i have been having for the last few months have been cause by this.

100% CPU usage, No audio over displayport, massive heat output from imac

I thought it was my PC and have bought a new power supply and 7970.