External monitor brightness control
September 6, 2017 6:33 AM   Subscribe

External monitor: can I force its brightness to actual zero without powering it off? (That is, without losing its window positions?)

I'm using a second monitor (Dell P2415Q) with a MacBook Pro 15" (early 2014, running OS 10.9).

On the Dell I have an arrangement of windows that's labor-intensive to recreate if I lose it. So I don't want to power off the Dell or physically disconnect it from the MacBook (because that snaps all windows back onto the MacBook's screen and I lose all my window positions on the Dell).

But often, I want to see only the MacBook's screen – I want the Dell to be at zero brightness. If I use the Dell's hardware buttons to turn its brightness all the way down to "0%," it's still very visible – when it's at what they call "0%," it seems to still be at 10% or more of its actual physical brightness.

Can I force the Dell down to true zero brightness, in a way that doesn't depend on traditional sleep/wake responses? (That is, can I have the Dell stay at zero brightness while I'm actively using the MacBook? I have one app that will always have windows open both on the MacBook screen and on the Dell, so I'll be 'active' in that app – also, I often accidentally move the mouse cursor into the external monitor's space.)

In other words, I want the Dell powered on and retaining everything currently on its screen, but not 'awakening' (not going above true-zero brightness) unless I mantually tell it to. Is this possible by any means?

Snowflake: I'm also running f.lux (on both screens) and I need a solution that will not override f.lux's control of gamma / color temps.
posted by kalapierson to Technology (8 answers total)
You're probably better off tackling the problem directly - i.e. finding a way of preserving window positions when monitors are plugged/unplugged.

Some apps that do this are Stay or perhaps Slate. See this helpful Stack Exchange answer.
posted by matthewr at 6:48 AM on September 6, 2017 [2 favorites]

Is there a way you can set a hotkey to trigger the screen saver on and off for that monitor, with the screen saver being a black screen? That's the direction I'd be looking in.
posted by Anticipation Of A New Lover's Arrival, The at 7:17 AM on September 6, 2017

I have a KVM to switch between my home (Mac) and work (Win 10) laptops which share a second monitor. Each thinks the external monitor is still attached when the KVM is active but the monitor is powered off. You could get a simple 2-port KVM and only use it for the monitor. Some are USB powered so you may have to connect one of the USB cables which will show up as an additional keyboard/mouse combo to the computer but this shouldn't cause a problem on a modern system. It's possible that you could power it using a USB phone charger or similar. This isn't the cheapest solution, but it should allow you to tun the power to the monitor off while the computer still thinks it's connected.
posted by Clinging to the Wreckage at 7:18 AM on September 6, 2017

In the meantime, while you're figuring out a tech-y solution, you could put a piece of black construction paper over the monitor. Or, if you're so inclined, a piece of artwork or one of those cheesy motivational posters.
posted by Elly Vortex at 7:47 AM on September 6, 2017 [2 favorites]

Yeah same as Elly my first thought was that this might be a problem best solved with a towel thrown over the monitor occasionally...
posted by brainmouse at 8:01 AM on September 6, 2017 [3 favorites]

Depending on how much heat the monitor produces, covering the back may not be good for the monitor, or fire safety.
posted by TheAdamist at 9:08 AM on September 6, 2017

I don't know how my setup is different, but I have a Macbook Pro (El Capitan) with an external Dell monitor set up as well. The Dell monitor is on the left of the laptop, and the display extends (isn't copied). When I turn off my Dell monitor, it just turns off. Everything stays where it is. Nothing shifts over to the laptop screen UNLESS I unplug the monitor from my computer.

So, maybe there's a setting you can use so you can just turn off the monitor. Or maybe it's the cable you're using. I have a dongle that I plug my monitor into that goes into a small square port on my macbook. I think it's called a MiniDisplay Port. The dongle I have is similar to this one or something like this.
posted by hydra77 at 12:03 PM on September 6, 2017 [1 favorite]

Response by poster: I don't think I've ever seen a wider variety of great ideas for one of my questions. Thank you all!
posted by kalapierson at 1:03 AM on September 8, 2017

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