Gamma Correction

Gamma correction is a brightness adjustment that mostly works on the midtones. Unlike a plain brightness control, which moves everything by the same amount, gamma changes the middle of the range and leaves the shadows and highlights mostly alone.

Here is the idea behind it. The brightness values stored in a video file do not line up evenly with the brightness you actually see on screen. A pixel sitting at the middle value does not display at exactly half brightness. A gamma curve describes that uneven relationship.

In video, gamma is usually a number between 1.0 (linear, rare in video) and 2.4 (the standard for Rec.709 broadcast). Higher gamma makes the midtones darker. Lower gamma makes them brighter. Either way, true black and true white stay about the same.

Common gamma values in video:

• Gamma 1.0 (linear). No correction. Used inside some workflows, rarely the final target.
• Gamma 2.2. A common standard for computer screens. The sRGB color space sits near it.
• Gamma 2.4. The standard for Rec.709 video (HD broadcast).
• Gamma 2.6. Sometimes used for cinema in dark theaters.
• PQ (Perceptual Quantizer). An HDR gamma curve made for high dynamic range content.
• HLG (Hybrid Log-Gamma). An HDR gamma made for broadcast that still works on standard screens.
• Log gammas (S-Log, V-Log, C-Log). Camera curves built to capture the most dynamic range. Log footage needs a gamma change to look right.

In real grading, gamma is one of three connected controls:

• Lift. Works on the shadows.
• Gamma. Works on the midtones.
• Gain. Works on the highlights.

The “gamma” in lift, gamma, gain is the midtone control, which matches what a gamma value does to the midtones.

Here are a few reasons gamma is so important in video.

It delivers the right color space. Different platforms expect different gamma. Broadcast TV expects Rec.709 gamma 2.4. Web video expects an sRGB-like gamma. Matching the target is key to accurate color.

It transforms log footage. Modern cameras shoot in log curves (S-Log, V-Log, C-Log) to capture the most range. Straight out of the camera it looks flat and gray. A gamma change brings it back to a natural look.

It adjusts the midtones on their own. Gamma controls the brightness in the middle of the range. Faces, products, and main subjects usually live there. So you can change how they look without touching the shadows or highlights.

It matches the screen. Different screens handle gamma differently. Mastering at the correct gamma helps the image look the way you meant on the target platform.

It handles HDR and standard video. HDR uses different gamma curves (PQ or HLG) than standard video (Rec.709). Gamma changes are part of moving between the two.

It shifts the feel of brightness. Gamma does not change the true brightest or darkest values, but it does change how bright the midtones feel. Raise it and things feel darker. Lower it and they feel brighter.

It works with contrast. Gamma and contrast affect each other. Changing the midtones changes how the shadows and highlights relate.

It is the foundation of a grade. Most grading starts with the right gamma. Get it wrong at the start and every later step is fighting that error.

It is camera-specific. Different cameras need different gamma changes. The same scene from two cameras may need different gamma to match.

For commercial work, gamma is mostly handled for you by color management. Modern software reads the source gamma and applies the right change. Hands-on gamma work is usually just for fine-tuning or special cases.

For log footage, the gamma change is the first big step in grading. Without it, log footage looks plainly wrong.

Here is how editors work with gamma.

Set the project’s working color space. Most color management setups let you pick a working space (Rec.709, Rec.2020, ACES, and so on). The right gamma comes along with it automatically.

Apply an input transform for log footage. Log footage needs a log-to-Rec.709 transform (or similar) to look right. Most software handles this with an input transform (an IDT in ACES) or a LUT.

Use the gamma control for the midtones. In the lift, gamma, gain controls, gamma handles the midtones. Raise it to brighten them, lower it to darken them. It is one of the most-used controls in basic correction.

Watch the waveform. The waveform shows how brightness is spread out. Gamma shifts the midtone values, and the waveform shows you exactly what is happening.

Apply an output transform for delivery. On export, your working space gets converted to the delivery space if they differ. ACES setups handle this with an output transform (an ODT).

Match gamma across cameras. A multi-camera project may have footage shot with different gamma. Bring it all to a matching base before any fine adjustments.

Be careful with gamma in compositing. Compositing steps like alpha blending and motion graphics can behave differently in different gamma spaces. Working in linear gamma for those steps, then converting back, gives cleaner results.

Lean on color management. Modern tools (DaVinci Resolve Color Managed, ACES, Premiere Pro’s interpretation settings) handle most gamma for you. Setting color management up correctly matters more than adjusting gamma by hand everywhere.

Save transforms as presets. When you use the same cameras a lot, saving the gamma transform as a preset speeds up the work.

Test on different screens. Gamma looks different from screen to screen. A pro reference monitor shows it accurately, while everyday screens vary.

Check the platform’s specs. Each platform documents its gamma requirements. YouTube, Netflix, broadcast, and theaters all have their own.

In most commercial work, gamma is mostly automatic through color management. Hands-on gamma work is reserved for log footage and fine adjustments.

Here are a few things that tend to go wrong with gamma.

Wrong gamma for log footage. Log footage left without the right transform looks flat and gray. The fix is applying the proper log-to-Rec.709 transform.

Mismatched gamma across cameras. A multi-camera project with different gamma on each camera. Without matching them, the cuts between cameras look obviously different.

Wrong working space. Setting the project to the wrong color space and gamma. Every later adjustment then fights that base error.

Skipping the output transform. Working in one color space but exporting without converting it. The delivered file ends up with the wrong gamma.

Compositing in the wrong gamma space. Compositing in a non-linear gamma blends incorrectly. You get edge artifacts, halos, or odd color shifts where layers meet.

Heavy gamma to fix exposure. Using extreme gamma moves to rescue badly exposed footage. It sometimes works, but often leaves banding or color shifts.

Wrong gamma for HDR. HDR needs specific gamma curves (PQ or HLG). Mastering with standard gamma for an HDR delivery gives wrong results.

Inconsistent gamma across the project. Different shots with different gamma applied. The whole piece feels uneven.

Crushed midtones from extreme gamma. Pushing gamma very high or very low makes the midtones look unnatural. Faces look off and skin turns unflattering.

Ignoring color management. Adjusting everything by hand when the software could automate it. The manual route is more error-prone.

Wrong gamma for the platform. Mastering at gamma 2.2 for broadcast (which expects 2.4), or the reverse. Subtle but real differences in how it shows.

For commercial work, gamma is mostly a technical detail that color management handles. Knowing what gamma is doing still helps when something goes wrong or when the automation does not get it right.