MacBook Air not filling entire screen on External Monitor

Question

MacBook Air not filling entire screen on External Monitor

I'm having trouble with my MacBook Air not filling the entire screen of my new Dell U2415 External Monitor.

There is a small black gap, all the way around the external monitor, when the MacBook Air is connected:

I tested the same monitor with a borrowed MacBook Pro, and it works perfectly. With the MacBook Pro, the screen is completely filled, using the same Mini Displayport cable:

It seems the issue is not with the Mini Displayport cable or the monitor, but with the MacBook Air.

What I've tried so far, with no results:

Replacing the Mini Displayport to Displayport cable with an Mini Displayport to HDMI cable
Resetting the NVRAM and SMC
Reinstalling macOS Sierra
Sprouting gray hairs in frustration
Gone through all of the resolutions in the macOS Display settings (while option-clicking)
(The closest I got to solving the problem was to choose an interlacing resolution. That got the screen all the way out to the edges, but had the disturbing side effect of making the image blur and shake)
Gone through all the monitor display settings on aspect ratio, color and presets

Setup and Specs

MacBook Air (13-inch, Mid 2013), 1.3GHz i5, 4GB RAM, Intel HD 5000
macOS Sierra 10.12.4
Dell U2415 External Monitor
Mini Displayport to Displayport cable

Does anyone have ideas to how to solve this issue? Thank you!

MacBook Air, macOS Sierra (10.12.4)

Posted on May 3, 2017 8:05 PM

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Answer 1

Top-ranking reply

Tobias Jensen Author

Level 1

15 points

May 4, 2017 5:36 PM in response to tjk

Hi tjk,

Thank you for looking into this.

Underscan

Unfortunately, the Underscan slider doesn't appear in the display settings for the Dell monitor, when I connect with the Mini Displayport to Displayport cable:

(The Underscan slider also doesn't appear if I connect the monitor with Mini Displayport to HDMI)

Exact matching resolution

I've looked into your other point, that my MacBook Air and my Dell monitor doesn't have a resolution that matches up exactly. It seems like my MacBook Air is outputting the exact native resolution of the Dell monitor (1920x1200 px). Here is what that looks like for me in the display settings:

Borrowed MacBook Pro (where the Dell monitor works)

I've looked into the specs for the borrow MacBook Pro, where the Dell monitor works exactly right when connected. I believe the model is a MacBook Pro (13-inch, Mid 2014), 2.6GHz i5, 8GB RAM, Intel Iris 5100, running macOS Sierra 10.12.4. For some reason, the MacBook Pro uses the entire display when outputting the 1920x1200 px native resolution to the Dell monitor, where the MacBook Air leaves a small black gap around the display when outputting the 1920x1200 px native resolution to the Dell monitor.

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Answer 2

Jan 10, 2018 10:50 AM in response to Tobias Jensen

Hi Tobias,

Wondering if you ever solved this issue. Interestingly enough, I have the opposite issue: black borders when I connect my Macbook Pro (late '13, Sierra) to a U2415. SwitchResX can help the issue but the resolutions that solve this issue result in a low resolution / jumpy image.

When I connect it to my friend's Macbook Air (early '15, Yosemite) - no bars / border. After scouring the web, I've seen a few suggest it's a graphics card issue.

Any updates on the predicament 8 months later?

Thank you.

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Answer 3

Rysz

Level 8

44,421 points

May 3, 2017 8:12 PM in response to Tobias Jensen

When you mirror your Mac Book to the external monitor, it displays pixel-for-pixel the same r solution on your external oontor, if the two resolutions are different, that's what you get. Change the redolution on your external monitor yo match the Display resolution on your MacBook.

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Answer 4

May 3, 2017 9:26 PM in response to Rysz

Hi Rysz,

Thank you for your reply. I have turned off the checkbox "Mirror Displays" in the macOS display settings, so that I'm running both my MacBook Air display and my external Dell monitor at their maximum native resolution (1440x900 and 1920x1200, respectively). The issues is that on my external Dell monitor, there is a small black gap all the way around the screen. For some reason, even though the resolution for the Dell external monitor is set to 1920x1200 in macOS display settings, there is still unutilized black pixels around the edge of the monitor.

This doesn't happen when I use a borrowed MacBook Pro. Using the exact same settings with the MacBook Pro, there is no black gap around the external Dell monitor (see the pictures above).

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Answer 5

tjk

Level 9

51,142 points

May 4, 2017 6:43 AM in response to Tobias Jensen

Hi,

It sounds like you have Underscan turned on. Mine does this when connected to a TV via HDMI with Underscan turned on, but not with my external display, which has a resolution which my MBP can match exactly. Go to System Preferences > Displays > click on Arrangement > select Mirror > click on Display > select the Dell monitor > Optimize for: Dell > Best for Dell > move the Underscan slider to Off.

If this isn't the issue, then your MBA and the TV don't have a resolution that will match exactly, so the TV is doing its own underscanning. Exactly which MBP is the borrowed one? It must have a resolution that matches up with the TV.

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Answer 6

tjk

Level 9

51,142 points

May 4, 2017 6:06 PM in response to Tobias Jensen

I was sure one of those would be the answer. 😟

Obviously something has to be different between the two Macs, and all I can think of is their native resolutions, but given what you've tried/seen, I don't know....

The only things that would seem to affect it, and I don't know how to fix it (unless there's a setting inside the Dell's menu, which I would definitely look at), are that the native resolutions of the two Macs are different, and one uses Thunderbolt 2 while the other is Thunderbolt. Somehow one of these two things, or something in the Dell's settings, must be affecting things.

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