Adjust definition in a photo in Photos on Mac
You can change a photo’s definition settings to add contour and shape as well as midtone definition and local contrast.
Note: You can also adjust the definition of a video. See Change and enhance a video.
In the Photos app on your Mac, double-click a photo, then click Edit in the toolbar.
Click Adjust in the toolbar.
In the Adjust pane, click the arrow next to Definition.
Drag the slider until you’re satisfied with the results.