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User profile for user: FrankPixel
FrankPixel Author
User level: Level 1
8 points

Resolution issue on macbook pro with dual 4k monitors

hey y'all, 


Ive looked thru the forum for help but I cant find an answer for my particular situation so I am hoping someone could offer some advice or insight.

I am probably not understand the capabilities of my Macbook and its relationship to my monitor setup


I have the i7 MacBook Pro (2.6, 16 gb, Intel UHD Graphics 630, Radeon Pro 555X 4 GB graphics)


I have 2 4k LG 27s, these here...

https://www.amazon.com/gp/product/B01C3BZIIC/


I have them connected via hdmi > adapters > thunderbolt or usb3? (I'm confused about this but currently looking it up). 

Here is a image to better explain...

https://share.getcloudapp.com/Z4uz2BXO


When going under display settings, the system allows me to put both monitors on 3840x2160 resolution. No problem, works fine, small lag but that is a separate concern and not the main issue. 


The problem is...


I cant seem to allow both monitors to be at the 2560x1440 resolution. I notice a difference in the setting options....

https://share.getcloudapp.com/L1uYylwD

You could see that LG1 has a different 'Resolution: Scaled..' options setup than LG2 (which does allow for the desired resolution) 


I am not understanding why my macbook is treating the two monitors different in this way and not allowing them to be on the same 2560x1440 resolution. Is it a limitation with the graphic card of the macbook or maybe the adapters I am using? Or are the combinations with the macbook and the kind of monitors I got no good?


I have tried switching around the hdmi cables and ports, this produced the same results. Individually, the monitors act the same way. Even without two monitors plugged in at the same time


Just for reference, I am mostly doing graphic design/media creation. 


There are probably other bigger questions that are related that I might need help understanding for example...

- I notice a slight lag with movement of mouse and browsers, opening apps, etc. I dont notice this when I am using just the machine without external monitors. Is this because 2/4k monitors at that display size 27inch) are expected to create such lag? Did I get the wrong monitors?

- If I am not using the 4k (3840x2160) resolution, is there any reason to even have these monitors be 4k? Could I return these and get something in the $150 price range with very low quality loss OR does using a 4k monitors at a lower resolution create much better quality than the lower end (non 4k) monitors. 


I should have asked this before the purchase but I think I got a bit excited and rushed into some of these decisions. 


Any guidance would be much appreciated :)

Thank you in advance

MacBook Pro 15”, macOS 10.14

Posted on Nov 9, 2019 11:18 AM

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
132,775 points

Posted on Nov 9, 2019 1:09 PM

(Actual) resolution, used for graphics, is shown as 3840 by 2160 one each of those two displays, in Deep 30-bit color. But with so much un-necessary data to re-paint the screen over HDMI, it can not keep up with the 60Hz refresh rate on both.


ONLY Text (NOT graphics) is scaled by 1.8 to resemble the size of a 1920 by 1080 display. That is the "User interface look like" number. Scaled text has more smooth edges than text at that actual size, because the diagonals and edges are anti-alised with more fill-in pixels during the scaling process.


If you use DisplayPort instead, it stops resending the entire screen every 60th second, and there will be time to have 60Hz refresh on BOTH displays at 30-bit deep color

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
132,775 points

Nov 9, 2019 1:09 PM in response to FrankPixel

(Actual) resolution, used for graphics, is shown as 3840 by 2160 one each of those two displays, in Deep 30-bit color. But with so much un-necessary data to re-paint the screen over HDMI, it can not keep up with the 60Hz refresh rate on both.


ONLY Text (NOT graphics) is scaled by 1.8 to resemble the size of a 1920 by 1080 display. That is the "User interface look like" number. Scaled text has more smooth edges than text at that actual size, because the diagonals and edges are anti-alised with more fill-in pixels during the scaling process.


If you use DisplayPort instead, it stops resending the entire screen every 60th second, and there will be time to have 60Hz refresh on BOTH displays at 30-bit deep color

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
132,775 points

Nov 9, 2019 12:02 PM in response to FrankPixel

1) It is a mistake to hook up these modern display using "Legacy" protocol HDMI. HDMI continues the tradition (needed for CRT displays) of sending the ENTIRE screen every 60th second. This clutter is completely un-necessary, as these fine displays have a display buffer and can be connected via DisplayPort family adapters.


2) If you wish to see the accurate information about displays running Scaled, use:


 Menu > about this Mac > ( system report) > graphics & displays...


... to get report like this one:


Displays:

Display:

Resolution: 2560 x 1600

UI Looks like: 2560 x 1600

Framebuffer Depth:


this will show the OVERALL resolution of the display, and also show that the TEXT ONLY is scaled so that the User Interface UI Looks like a larger size to avoid its being illegibly tiny.




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User profile for user: FrankPixel
FrankPixel Author
User level: Level 1
8 points

Nov 9, 2019 12:21 PM in response to Grant Bennet-Alder

Thanks for the response Grant.


I did see the DP cables that came with the monitors and from what I understand from your reply and what I have read about (HDMI vs DP) I should be using the DP cables for best results.

It looks like I will have to get adapters for that, but Im looking forward to seeing the results.


I did get that report


LG Ultra HD:


  Resolution: 3840 x 2160 (2160p 4K UHD - Ultra High Definition)


  UI Looks like: 1920 x 1080 @ 30 Hz


  Framebuffer Depth: 30-Bit Color (ARGB2101010)


  Main Display: Yes


  Mirror: Off


  Online: Yes


  Rotation: Supported


  Automatically Adjust Brightness: No


  Connection Type: DVI or HDMI


  Adapter Firmware Version: 7.55


LG Ultra HD:


  Resolution: 3840 x 2160 (2160p 4K UHD - Ultra High Definition)


  UI Looks like: 1920 x 1080 @ 60 Hz


  Framebuffer Depth: 30-Bit Color (ARGB2101010)


  Mirror: Off


  Online: Yes


  Rotation: Supported


  Automatically Adjust Brightness: No


  Connection Type: DVI or HDMI


  Adapter Firmware Version: 7.55


I understand that the default resolution is 3840x2160 but its being scaled down to 1920 so that the text doesn't seem so tiny which it is on 4k, but I am still unsure on how or why I cant have both monitors be at 2560x1440. Or are you suggesting that this will be allowed once I start using DP cables?


Thanks

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Resolution issue on macbook pro with dual 4k monitors

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