macOS Sierra no longer supports ultrawide monitors?

Hi, same problem with my late 2012 MacBook pro and my new (and working great in el cap) LG UltraWide 29UM58.

I want anyone else who has this combo to know that the SwitchResX fix did not work in my case, so just keep in mind that YMMV.

Why do you assume that among Apple's employees and testers that someone happens to have one of the monitors experiencing this issue?

It's inevitable that as soon as a product is released, issues like this turn up as Apple can't have one of every conceivable configuration, nor can testers necessarily have one.

I had the same problem with the 29" LG Ultrawide w/ HDMI only, while I didn't have any problem with the 34" LG Ultrawide w/ Thunderbolt.

I just upgraded to the latest Sierra 10.12.1 and it's fixed!

It's incredibly clear and way better than it was using SwitchResX which letterboxes left and right using 2560x1440 and loses the high resolution too.

Thank you apple!

I FINALLY found the fix! I've read so many threads on the Ultrawide monitors in the recent month. I'm using an LG 34" (IPS LED) Ultrawide "diagonal" monitor and was unable to view the image properly, it stretches horizontally and I'm using it behind an easel while painting with oils on canvas, referencing videos and photos is very important during the final glazes. Anyway, I tried various cables, various adapters, option key (of course), the SUDO command (reversed command after it did not work), all with the same image/display results; yes I could see the image but it was a maximum display of 1920 (or 1080p) and not showing the 2560x1080. The app idea is ok however, after reading the details, the app only scales/stretches instead of allowing or enhancing the actual quality of the image. I read above that the Apple customer service's last given advise was to use a "hub" and I had totally forgot that I use the Elgato hub, purchased one with each Mac, recently. The Thunderbolt 2 Dock does have drawbacks, in my opinion and during my experience, i.e., undocking or ejecting peripherals overnight, for instance, which is why I didn't connect it sooner.

Long story short, I'm attaching an image of what you want to see when using the UltraWide monitors, the display default is correct for the LG display (I bet the curve will work brilliantly for my requirements).

THANK YOU FOR ADDING THE INFORMATION TO FIX THIS!

Finally!

in Display pane double tap the scaled while using the option key.

Did you find a work around?

Hi,

i'm having the same problem but with my LG 25" ultra wide. Im trying the SwitchResX route, but not having much joy.

You got it to work ok then?

But the um68 was much better?

Thanks

Hi,

i'm having the same problem but with my LG 25" ultra wide. Im trying the SwitchResX route, but not having much joy.

You got it to work ok then?

But the um68 was much better?

Thanks

I had the same problem. Simply solved by replacing the mini Display to HDMI by a mini Display to Display cable. Cost less then 10 euro. Works for me under Sierra & High Sierra.

Hi - This is an old thread, by I own a lat 2012 MBP and am ordering a couple of LG UltraWide 29UM58 monitors. Were you ever able to fix this issue?

Thanks!