Setting The Brightness on an External Macbook Monitor

You can always tell the difference between Broadcast Engineers and IT professionals. Broadcast Engineers will be at least one software update behind on their phones and gadgets!

There’s good reason for this - the latest software updates are nearly always untested in a real-world environment and in the broadcast world this can make the difference between being on air and falling off air. As a result we tend to err on the side of caution and only update when there’s plenty of time to do a thorough test of important functionality. It’s the classic case of “if it ain’t broke, don’t fix it”.

Today’s battle was a small but annoying one that occured after updating a Macbook Pro to Monterey. An external Apple HD LED Cinema display decided that it would reset brightness to 100% every time the macbook woke from sleep.

This display was in an edit suite with carefully balanced lighting to aid viewing and colour correction of broadcast video. So this peculiar bug resulted in an intense retina-destroying brightness that would cause even the most acclimatised Gremlin to shout “Bright Light!”

Gizmo Gremlin Bright Light

With the monitor being out of support it’s unlikely Apple will be in any hurry to sort this issue, because that doesn’t generate sales of new monitors of macbooks does it? We’re expected to toss our expensive electronic product in the bin and immediately upgrade to the latest model.

Fortunately there is a solution: ddcctl.

ddcctl allows the user direct access to the DCC or Display Data channel, which is a collection of protocols that enable the display and the computer to talk to each other. Amongst other things, these commands can be used to change the brightness and contrast of the external display from the computer.

Follow the instructions on the github page to install it on your mac (I used homebrew as I already had it installed):

I then used terminal to issue the command: ddcctl -d 1 -b 50

This tells the macbook to set monitor 1 (the external monitor) to a brightness of 50%.

I just need to write an apple script or similar script to issue this command everytime the macbook wakes or the screen is plugged in. That’s work in progress and I’ll update this page as soon as I’ve completed it.

But for now, this utlity and command might help you prevent the logo of an apple being permanently part of your persistence of vision!

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