hdmi-vs-displayport-settings

Overview

LG 4K HDR monitors have different settings available depending on connection type. Some settings are HDMI-only because DisplayPort handles them automatically (in theory).

HDMI-Only Settings

Black Level

What it does: Adjusts RGB range between Limited (16-235) and Full (0-255).

Low = Limited RGB range (16-235) - for devices outputting limited range
High = Full RGB range (0-255) - for PCs outputting full range

Why HDMI-only: DisplayPort defaults to Full RGB automatically, so the setting isn’t needed.

HDMI Ultra HD Deep Color

What it does: Unlocks full HDMI 2.0 bandwidth for 4K@60Hz with full color.

Setting	Result
OFF	Limited to 4K@30Hz or 4K@60Hz with 4:2:0 chroma
ON	Full 4K@60Hz with 4:4:4/4:2:2 chroma support

Why HDMI-only: DisplayPort natively supports full 4K@60Hz bandwidth without needing a special mode.

To enable:

Open monitor OSD menu
Navigate to Picture/Input settings
Find “HDMI Ultra HD Deep Color”
Set to ON for the HDMI port you’re using

Problem: DisplayPort Shows Washed Out Blacks

Symptoms

Blacks appear gray/washed out on DisplayPort
Same monitor looks correct on HDMI
Colors look dull or faded

Cause

macOS sometimes sends Limited RGB (16-235) over DisplayPort, but the monitor interprets it as Full RGB (0-255). This mismatch causes:

Black (16) displayed as dark gray
White (235) displayed as off-white
Overall washed out appearance

This is a known macOS bug, especially on Apple Silicon Macs.

Solutions

Solution 1: Disable HDR (Try First)

System Settings → Displays
Select the DisplayPort monitor
Uncheck “High Dynamic Range”

Solution 2: Change Color Profile

System Settings → Displays
Select the DisplayPort monitor
Try different color profiles:
- “Generic RGB”
- Any non-HDR LG profile

Solution 3: Use BetterDisplay App (Recommended - Works!)

BetterDisplay can force RGB Full Range mode on DisplayPort.

brew install --cask betterdisplay

Step-by-step:

Launch BetterDisplay (runs in menu bar)
Click the menu bar icon → find your DisplayPort monitor (e.g., “LG HDR 4K”)
Expand Color Mode section
You’ll likely see it defaulted to something like “10-bit YCbCr 4:2:2 Limited Range”
Select: “8-bit SDR RGB Full Range”
Blacks should improve immediately
Click “Configuration Protection” to make the change persistent across sleep/restart

Why this works: macOS defaults to Limited Range over DisplayPort. BetterDisplay forces Full Range, matching what your monitor expects.

Solution 4: EDID Override (Advanced)

Force RGB output by creating a custom display profile:

See GitHub Gist for M1 Macs
Generate override plist for your display
Install to /Library/Displays/Contents/Resources/Overrides/
Sleep and wake Mac to apply

Solution 5: The Sidecar Trick

A quirky workaround that resets color output:

System Settings → Displays
Enable AirPlay/Sidecar mirroring to any device
Immediately disable it
Colors often reset to correct values

Solution 6: Toggle Refresh Rate

System Settings → Displays
Change refresh rate: 60Hz → 50Hz
Change back: 50Hz → 60Hz
This can reset the color mode

Solution 7: Use USB-C to DisplayPort Cable

macOS Sonoma (14) and Sequoia (15) reportedly output correct RGB when using USB-C to DisplayPort cables instead of native DisplayPort.

Why HDMI Works Correctly

On HDMI, you can manually set Black Level to match what your Mac outputs:

Mac outputs Full RGB → Set Black Level to High
Mac outputs Limited RGB → Set Black Level to Low

DisplayPort lacks this monitor-side adjustment, so you must fix it on the Mac side.

Recommended Setup

Connection	Settings
HDMI	Enable “HDMI Ultra HD Deep Color”, set Black Level to match Mac output (usually High for PCs)
DisplayPort	Use BetterDisplay or EDID override if blacks look washed out