LG ultra wide screen

This worked for me as well, but only after I adjusted a few more of the parameters (maybe we have slightly different LG models?) I started with the parameters from the "Export EDID" file and then edited the pixel clock to 148.50 as you did. My settings :

Posting in case anyone gets here from Google the same way I did. In summary, these are the steps I took to make this work:

1. Disable SIP

2. Install SwitchResX

3. Select your monitor in the SwitchResX Preferences

4. Export EDID and save to a file on your desktop

5. Open the file

5A) In the "Monitor Description blocks" section, find the resolution you want (in my case 2560 x 1080 @ 60.000Hz)

5B) Also find the resolution that your computer is currently using (in my case 1920 x 1080 @ 60.000Hz)

6. Create a custom resolution for your monitor. Copy the exact settings from step 5A. If the vertical and horizontal polarity are negative, uncheck the "Positive sync" checkboxes.

7. Save (requires your Mac password) and reboot. If it works, great. If monitor says "Out of range", continue to step 8:

8. Find the Pixel Clock setting from step 5B (not 5A!) and use that for your custom resolution. This should cause the Vertical scan rate setting to change to something other than 60 Hz; this is fine. Save & reboot, and your monitor should work.

Yes, me too.

this display was working perfectly in 2560x1080, but now with sierra the best resolution from system preferences is "1080p". I also tried a custom resolutions 2560x1080 with SwitchResX, but it is not working.

any idea?

I have exactly the same problem. And is very annoying. Right now, I have to work with the screen of my macbook pro, waiting for a solution from Apple or LG.

Instead of using SwitchResX try doing this natively in OS Sierra:

1. Make sure display is plugged into the coputer
2. Open "Apple Menu" -> "System Preferences..." and select "Displays"
3. One window should open up on each connected display. Each window corresponds to settings for that particular display
4. On the LG's window, hold down the Option Key while selecting "Scaled" next to "Resolution"
5. You should now see more resolution 'options' than normal. I think thats why they call it the option key.

I hope this helps!

The max. option that allows me is 1080p, and I had, with OSX 10.1, 2560 x 1080...

Thank you, anyway

I will follow this post for solutions.

thank you for help. But already did this without success... :-(

same problem here, this *****!!!!!

Also experiencing the same issue. Hope they patch this soon or we'll be forced back to PC....

I have this problem for both a 15in retina macbook pro and 17in macbook pro, with thunderbolt and HDMI. Have tried the option key on display and also the 3rd party display software. My best guess is the newer sierra HDMI driver is not recognizing all the possible resolutions sent over by the LGultra wide display

Temporary solution :

Go to the monitor setting and change aspect ratio as 'original' from the monitor side.

monitor menu/quick settings/ratio/original.

Hope it works for you,, i was on the chat with some pretty smart people yesterday. We did all sorts of things to try and make it work. I ran out of time after a few hours. We tried these things and they didn't work

(1) sudo defaults write /Library/Preferences/com.apple.windowserver.plist DisplayResolutionEnabled -bool true

(2) reset pram

(3) reload OS from restore

(4) try with thunderbold to hdmi converter

we came to the conclusion that the HDMI driver for sierra is not getting the same information that El Capitan driver got. I guess we have to wait for a fix,

I reported this "bug" in the feedback with macOS Sierra Beta. Really! I got believe that something like is can slip through QA; why ask for beta feedback if no is going to take heed of them.

I could make my LG ultrawide monitor work properly with SwitchResX, but after 2 more steps:

1 - I disabled System Integrity Protection before installing SwitchResX (http://www.madrau.com/support/support/srx_1011.html)

2 - I created a custom resolution based on the 1080P60 (automatically detected), just changing the first resolution parameter from 1920 to 2560 (don't forget to save and reboot the computer after creating the custom resolution - check the status column next to the resolution created). Those are the parameters of the custom resolution:

I've been searching and trying fix this problem for three days, after upgrading to Sierra. I hope it helps!!