The Curve adjustment tool is one of the most versatile tools in Capture One. After making adjustments in the Levels tool, the Curve tool is used to further adjust the contrast and color balance.
There are five curves in total in the Capture One Curve tool. Similar to the Levels tool, the curves are adjusted independently. The combined RGB curve and optional Luma curve are both used to adjust contrast and brightness. The latter one has the additional benefit of not increasing saturation.
The Luma curve also prevents banding and abnormal artifacts that are sometimes visible in transitions between colors, even when making more extreme adjustments. Images processed using earlier versions of Capture One Pro must be updated using at least the Capture One 9 engine before being able to edit images using the Luma curve. Capture One’s Curve tool may also be used to adjust color balance of the image using the individual color channels (Red, Green, and Blue).
All five curves share similar characteristics. The lower-left and upper-right zones of the slope denote the shadow and highlight regions of the image respectively, while the area in the middle represents the mid-tones. By adding control points to the slope, you define the input values (represented by the horizontal axis). By adjusting it, you define the desired output values (represented by the vertical axis of the graph).
When modifying the slope to that of a curve, the tool applies the contrast and color adjustments by either stretching or compressing tones in the shadow, mid-tone, and highlight areas.
Although the Curve tool can be used to set the black and white points, it is usually best to do so with the Levels tool. The Curve tool allows greater flexibility and control of shadow mid-tones and highlights, particularly when the panel is undocked from the tool tab and expanded.
Curves adjustment can be applied to layers for selective adjustment.