Hybrid Log-Gamma (HLG) is an HDR standard designed for live broadcasts that works on both modern 4K TVs and older SDR screens without needing metadata.
You just bought a new 4K TV. You see acronyms like HDR10, HDR10+, and Dolby Vision plastered on the box. Then, you dig into your picture settings or tune into a live sports match, and you see a new term: HLG.
This isn’t just another marketing buzzword. It solves a specific problem that other formats cannot fix.
Most High Dynamic Range (HDR) formats are great for streaming movies on Netflix or playing Blu-rays, but they are terrible for live cable or satellite TV. Broadcasters needed a way to send high-quality signals that wouldn’t look broken on older, non-HDR televisions. HLG is that solution.
How Hybrid Log-Gamma Technology Works
To understand HLG, you have to look at how TVs handle light. Standard televisions use a “gamma” curve to determine how bright specific parts of an image should look. This works well for standard content but limits the detail in very bright or very dark areas.
HLG combines two different methods into one signal:
- Gamma curve: Handles the darker parts of the image and the mid-tones. This is the signal that standard, older TVs recognize.
- Logarithmic curve: Handles the extremely bright highlights. This extra data sits on top of the signal, which only HDR-compatible TVs can read.
This combination allows broadcasters like the BBC or DirecTV to send out a single video feed. If your TV is new, it reads the “Log” part and displays brilliant HDR highlights. If your TV is old, it ignores the “Log” part and just displays the standard “Gamma” image. This backward compatibility makes HLG unique in the display market.
Origins of the format
Two major broadcasters developed this standard specifically to fix transmission headaches. The BBC (British Broadcasting Corporation) and NHK (Japan’s public broadcaster) created HLG. They needed a format that didn’t require massive amounts of bandwidth or separate feeds for different TV models.
Comparing HLG To HDR10 And Dolby Vision
Most consumers know HDR through streaming services. When you watch a blockbuster movie, you are usually watching HDR10 or Dolby Vision. HLG operates differently from these formats.
The Metadata Difference
HDR10 and Dolby Vision use “metadata.” This is extra instruction code sent alongside the video that tells your TV exactly how to tune the brightness and color for every scene (or even every frame). While this produces stunning quality, it is difficult to encode during a live event like the Super Bowl or the World Cup.
HLG does not use metadata. Instead, it relies on the physical properties of your display. The TV takes the signal and calculates the light output based on its own capabilities. This makes HLG slightly less precise than Dolby Vision for cinematic movies, but it makes it infinitely faster and easier to transmit over cable and satellite waves.
Quick comparison:
- Dolby Vision: Uses dynamic metadata. Best for movies. Not backward compatible with SDR TVs.
- HDR10: Uses static metadata. Standard for discs and streaming. Not backward compatible.
- HLG: No metadata. Best for live TV. Fully backward compatible with SDR.
Why Broadcasters Prefer HLG
TV networks operate on tight bandwidth budgets. Sending two separate signals—one for 4K HDR owners and one for standard HD owners—is expensive and technically difficult. It doubles the amount of data they must push through the pipeline.
According to the International Telecommunication Union (ITU) standards, efficiency is key for global broadcasting. HLG allows networks to use a single distribution workflow. A camera operator at a soccer stadium shoots one feed. That feed goes to the production truck, up to the satellite, and down to your house. Your TV decides how much of that data it can use.
This efficiency is why you will see HLG popping up mostly on:
- Live Sports: The Olympics, World Cup, and Premier League broadcasts often utilize HLG.
- News Broadcasts: Some high-end news productions test this for studio lighting.
- User-Generated Content: YouTube supports HLG uploads because it simplifies playback across billions of different devices.
Using HLG For Photography And Video
HLG is not limited to your living room TV. It has become a favorite tool for videographers and content creators. Cameras from Sony, Panasonic, and Canon now include HLG recording modes.
Why creators shoot in HLG:
- Speed: Creators can shoot high-dynamic-range footage that looks good immediately without spending hours color grading on a computer.
- Safety: It preserves highlight details (like bright skies) that would normally blow out to pure white in standard recording modes.
- Workflow: It integrates easily into editing timelines meant for YouTube HDR delivery.
If you own a modern mirrorless camera, you might see “HLG1,” “HLG2,” or “HLG3” in your picture profile settings. These modes allow you to capture more dynamic range while keeping the file easy to view on standard monitors.
Checking If Your TV Supports HLG
The good news is that hardware support for HLG is widespread. Since the standard was finalized around 2016, almost every major TV manufacturer has adopted it. If you bought a 4K HDR TV from Samsung, LG, Sony, Vizio, or TCL after 2017, you likely have support built-in.
Steps to verify support:
- Check the manual: Look for “Hybrid Log-Gamma” or “HLG” in the specifications section.
- Run a YouTube test: Search for “4K HLG HDR test” on the YouTube app built into your TV. If your TV switches into HDR mode (often indicated by a small popup badge in the corner), you are set.
- Inspect input settings: Some TVs require you to manually enable “Enhanced HDMI” or “Deep Color” on specific HDMI ports to accept HDR signals from cable boxes.
Tech tip:
Just because a TV supports HLG doesn’t mean it handles it perfectly. Because HLG relies on the TV’s own brightness capabilities, a budget TV with low peak brightness (under 400 nits) might make the image look dimmer than standard HD. This is a hardware limitation, not a flaw in the signal itself.
Troubleshooting Common HLG Picture Issues
Sometimes switching to an HLG channel makes the picture look washed out or grey. This usually happens when there is a mismatch between the cable box and the TV.
Fixing washed-out colors
If the colors look flat, your TV might not be detecting the HLG flag in the signal. You can usually force the TV to switch modes.
- Open Picture Settings: Navigate to your TV’s expert or advanced picture menu.
- Find Gamma Settings: Look for an option labeled “Gamma” or “EOTF” (Electro-Optical Transfer Function).
- Select HLG: Manually change this setting from “2.2” or “BT.1886” to “HLG.”
Once you make this switch, the contrast should snap back to normal, with bright highlights and deep shadows. Just remember to switch it back to “Auto” when you are done, or your normal TV channels will look strange.
The Future Of Broadcast Standards
Streaming is moving toward Dolby Vision and HDR10+, but broadcast TV moves slower. Changing the infrastructure of satellites and cable lines takes decades. Because HLG bridges the gap between the old and the new, it remains the standard for broadcast TV for the foreseeable future.
For more deep dives into broadcast technology, BBC R&D maintains excellent documentation on how they deploy these signals globally.
As live sports production shifts entirely to 4K, HLG will ensure that viewers with top-tier OLEDs get the brightness they paid for, while viewers with older 1080p sets can still watch the game without a glitch.