Avoiding gamma shift when exporting from Resolve

In this post, I describe how to fix two types of gamma shifts in Resolve

• Gamma tag gamma shift
• Use Mac Display color profiles for viewers gamma shift

Rec709-A gamma tag gamma shift fix

Video files from Final Cut Pro X and other sources are often tagged as Rec.709-A, even if they were graded on monitors calibrated to 2.4 gamma. This can lead to inconsistencies in color representation across different platforms and workflows.

In some cases, you may need to set the Timeline Color Space in DaVinci Resolve to Rec.709 Gamma 2.4. One such instance is when converting a 2.4 gamma video file to a Digital Cinema Package (DCP), as discussed in my previous post.

When exporting a DCP back to a video file from a Rec.709 Gamma 2.4 project, the video that was originally tagged as Rec.709-A will be tagged as 2.4 gamma. This can result in the film appearing darker than the original when viewed in QuickTime Player on Macs or on platforms like Vimeo and YouTube.

To address this issue, use the Rec.709-A gamma tag as the output color space when exporting from Resolve, while maintaining the timeline color space as Rec.709 Gamma 2.4. This approach ensures that the exported, converted video file will appear consistent with the original when opened in QuickTime Player on Macs or viewed on Vimeo and YouTube.

Method 1 – Changing Project Settings

In Project Settings – Color Management – Color Space & Transforms
Tick Use separate color space and gamma
In Timeline color space – Rec.709 – Gamma 2.4
In Output color space -Rec.709 – Rec709-A

Method 2 – Changing Advanced Setting when exporting

Project Settings – Color Space & Transforms – Color Space & Transforms
Output Color space – Same as Timeline (default)

When exporting in the deliver pane, you change the tag in:
Advanced Settings
-Color Space Tag – Rec.709
-Gamma Tag – Rec.709-A

Checking the gamma tags in Quicktime Player (Mac)

The original QuickTime from Final Cut X had these tags:
Color Primaries: ITU-R BT.709
Transfer Function: ITU-R BT.709
YCBCr Matrix: ITU-R BT.709
Code Points: (1-1-1)

The Quicktime with the Rec 709, 2.4 gamma tag that was darker than the original,
was recognized in QuickTime player as:
Color Primaries: ITU-R BT.709
Transfer Function: Unspecified (2.4)
YCBCr Matrix: ITU-R BT.709
Code Points: (1-2-1)

The exported Quicktime with the Rec.709-A tag has the same tag as the Final Cut X QuickTime and does not have a gamma shift in Quicktime player or YouTube.

Color Primaries: ITU-R BT.709
Transfer Function: ITU-R BT.709
YCBCr Matrix: ITU-R BT.709
Code Points: (1-1-1)

Use Mac Display color profiles for viewers gamma shift fix

Using Rec.709 -A as the timeline and output color space

When working on a Mac with “Use Mac Display color profiles for viewers” enabled in DaVinci Resolve, using sRGB as the timeline color space will prevent gamma shifts between QuickTime Player and Resolve. However, it’s important to note that the sRGB tag is not recognized by popular streaming platforms like YouTube and Vimeo.

For deliveries intended for YouTube and Vimeo, a more effective approach is to set both the timeline color space and output color space to Rec.709-A. This configuration ensures consistent gamma representation across these platforms, avoiding unintended shifts in brightness or contrast.

Project Settings – Color Management – Color Space & Transforms
In Timeline color space – Rec.709 – A
In Output color space – Same as Timeline

The Rec-709-A tag is expected and matches Resolve, QuickTime player, Youtube, and Vimeo.

Rec709-A in Resolve compared to Rec709-A in Quicktime player

There is no gamma shift

Rec709-A in Vimeo compared to Rec709-A in Quicktime player

There is no gamma shift

Rec709-A in YouTube compared to Rec709-A in Quicktime player

There is no gamma shift