After 10.6.8 Mini Displayport to HDMI PROBLEM

It works with the mountion lion upgrade. Brightness control is working well.

In 10.8.2 it is working? In this thread, a guy said that it wasn't.

https://discussions.apple.com/thread/3173142?start=0&tstart=0

Giving this thread a bump. I went through a long period where the problem could be fixed whenever it cropped up by restarting in Safe Boot mode, then restarting again. Had a good long run of success with that, but it ended today when I allowed Software Update to do it's thing -- security update, Java update, HP Printer update, iTunes update. BIG mistake!

No amount of reboot/unplug/replug displayport cable appears to do the trick. I saw the referenced thread that suggests Mt. Lion does NOT solve the problem, but with a single recent data point and at least one older that said Mt. Lion DID solve it, I'm left wondering. Anyone else see this problem resolved with Mt. Lion?

Anyone know how to revert the OS to 10.6.7 without a Time Machine backup?

Is it that the brightness controls aren't working, or it won't go into target display mode at all?

FOr mr mt lion is a work around at best.

I Can now use target display mode with out the iMac running at 100% amd over heating. I can also change the brightness but it resets every time I switch between computers.

MY solution is sell the iMac and buy a 27" standalone monitor with multiple inputs and a mac mini.

BUt the way apple is going I may just drop the mac altogether. The better experience of osx is being ruined by arrogance on apples part.

Brightness controls don't work. It never fails to enter Target Displaly mode when connected (via my Monoprice displayport-to-diplayport cable) to my MBPr's Thunderbolt port. It does NOT enter Target Display mode if connected (via the same cable) to my Thunderbolt Cinema Display's TB port, but I assume that's expected.

Oddly, Brightness controls are working after yet another Shut Down / Safe Boot / Restart cycle. The only difference between the latest cycle and the previous couple attempts: I accidentally left the displayport cable connected between iMac and MBPr-attached TB Cinema Display, and tried to put it into Target Display mode in while in Safe Boot, then again after restart. When the latter failed, I realized the cable was still plugged into the Cinema Display. Plugged it directly into the second TB port on the MacBook, put it in Target Display, and found the brightness controls are working again.

I've been running this setup long enough to know that the brightness controls won't work if, when I switch to Target Display mode, the iMac's screen doesn't automatically (and immediately) adjust itself to something dimmer than "blindingly bright."

@merve0o0: Are you saying that your displayport iMac 27" running Mountain Lion always responds to the brightness control keys when you switch it to Target Display mode? And if so, which rev (10.8.__) are you on?

TIA!

Yeah, I've been waiting to update to ML because I was worried about Final Cut Pro 7 not working. Now I've gotten into a good flow with Premiere. And I actually need to update for some software. I've bought it and have it running on my MBP. So this was the one thing still holding me back from updating to ML on the iMac. So it sounds like it's working ok then, after your update? I don't think I've done a system update on this iMac since I got it in 2010. I know that's not safe since I need the security patches, but I use this feature a lot.

My iMac is still on OS 10.6.8, but did run the Software Update this morning. No idea why the Brightness controls stopped working after the Update earlier in the day, nor why cycling through several iterations of the Shut Down / Safe Boot / Restart / Target Display steps failed to get them working, nor why they've started working again after one more cycle this afternoon.

Hope you'll post your experiences here if you do migrate your iMac to ML.

Yea the f1/f2 keys on my imac keyboard adjust the brightness everytime now. it just wont auto adjust like it used to on 10.6.7.

iMac is on 10.8.2

Ah, ok. I was thinking you were on ML. Yeah, I'm on 10.6.7 and it works perfectly. 10.6.8 is when the feature broke (the brightness controls stopped working).

I had it confirmed by someone that the feature was working correctly in the most up to date (that was January) version of Mountain Lion.

Here's the thread. Start with my post at #15.

http://forums.macrumors.com/showthread.php?t=1518665

So I would say go ahead and update to ML and you'll probably be set. Now that I'm thinking about it again, I'll probably do mine next week. If so, I'll post back. If you update first, let me know how it goes.

Oh, and btw, I recommend disconnecting any monitor (whether it's an input or output) when doing system/ OS updates. I had a terrible experience with my MBP a few years back when I did a software update and I think the cause was that I had it hooked up to a monitor at the time. It took a few months until the next update to fix it. I don't remember specifics, but it had to do with the display not turning off or turning on or something.

This is all why I thoroughly research any OS updates, and probably led to me not updating other software or mobile apps before I can confirm that it works properly.

Thanks for the feedback. I wonder if it will still work in ML 10.8.3? I don't have an install disk for ML, and presume an AppStore download would now be 10.8.3...

AFAIK, they stopped making install disks. So either an install from the App Store, or a download from the App Store that is put onto a bootable USB drive (not sure exactly how/ if that works) are the only ways. I would really, really hope that they didn't screw it up again that fast. But I guess it is worth checking to be sure. lol.

I'll let you know, but you're likely to beat me to it. Now that it's working again, I'm unlikely to toggle out of Target Display anytime soon. It may only be a correlation, but it seems like toggling in and out of Target Display a few times between iMac restarts has no impact on the iMac's f1/f2 buttons functioning properly. There always comes a point where toggling into Target Display brings the iMac's screen in at "Blinding Brightness" that cannot be turned down.

I know when I hit the point where the Safe Boot / Restart cycle fails consistently to restore the brightness controls, I'll make the leap unless you and/or others report that ML isn't a consistent solution. Thanks for sharing the link.