Curves Adjustment

Discover how to use the Curve tool and accurately adjust the overall color and contrast in the shadow, mid-tones and highlights in the combined RGB mode, as well as control color in the individual color channels.

An overview of the Curve tool

The Curve adjustment tool is one of the most versatile tools in Capture One. After adjustment in Levels the Curve tool is used to further adjust the contrast and color balance.

In the Capture One Curve tool there are five curves in total, and like the Levels tool, these are adjusted independantly. The combined RGB curve and optional Luma curve are both used to adjust contrast and brightness, with the latter having 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 (Red, Green and Blue) color channels.

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) and, by adjusting it, 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 shadows mid-tones and highlights, particularly when the panel is undocked from the Inspector and expanded.

Curves adjustment can be applied to layers for selective adjustment, see the Layer Adjustment section for details.

Improve contrast Pro

Curves enables users to further adjust the overall tonal distribution of an image within the shadow and highlight limits that are set by the Levels tool. Like Levels, the Curve tool has several channel modes to choose from depending on your intent. The combined RGB mode is used to adjust contrast and lighten or darken an image, collectively known as tonality.

  1. Go to the Exposure Inspector.
  2. From the Curve dialog, select the RGB tab.    
  3. Click directly on the slope to add a control point in the tonal region that you want to adjust. (The upper-right of the slope adjusts highlights, and the center adjusts mid-tones. The bottom or lower-left adjusts the shadows.)
  4. To lighten or darken the selected region, select and drag (or scroll) a control point up or down respectively, to form a curve.
  5. To decrease or increase contrast in the chosen region, click and drag the control point to left or right respectively.
  6. Add more points to the curve to adjust other areas. (To remove a control point, click and press delete/backspace or drag it off the curve.)
  7. As an option, you can also add points by selecting the Curve Point Picker and clicking on the area of your image that you want to adjust in the Viewer.

Improve contrast without altering saturation Pro

The combined RGB mode is usually the first choice for fine-tuning contrast in most images, however, increasing contrast typically results in an increase in saturation. This can be confirmed by checking the color values, before and after adjustment.

It may be acceptable in landscapes but for certain images such as portraits, an increase in saturation may not be desirable. When that's the case the Luma mode should be adopted instead. In most respects the Luma curve can be adjusted in the same way that you would adjust an RGB curve. In fact, with more extreme adjustments, the Luma curve has a more realistic response. 

  1. Go to the Exposure Inspector.
  2. From the Curve panel, select the Luma tab.
  3. Click directly on the slope to add a control point in the tonal region that you want to adjust. (The upper-right of the slope adjusts highlights, and the center adjusts mid-tones. The bottom or lower-left adjusts the shadows.)
  4. To decrease or increase contrast in the chosen region, click and drag the control point to left or right.
  5. To lighten or darken the selected region, drag a control point up or down.
  6. Add more points to the curve to adjust other areas. (To remove a control point, click and press delete/backspace or drag it off the curve.)
  7. As an option, you can also add points by selecting the Curve Point Picker and clicking on the area of your image that you want to adjust in the Viewer.

 

Set black and white points (optional) Pro

The tone curve has moveable anchor points located at either end, one in the shadows and another in the highlights. They enable you to set black and white points (remap the darkest and lightest values in the tonal range), like the Levels tool. Indeed, if the black and white points have been previously set using the Levels tool, it is not necessary to make adjustments to the anchor points.

  1. Go to the Exposure Inspector.
  2. In the Curve Tool, position the cursor on one of the anchor points – a guideline will be displayed to help with the positioning.
  3. Click and hold the anchor point and then drag it to the desired position. For example, to remap the tonal range, move the anchor points inwards horizontally so that the guidelines just touch the edge of the histogram.
  4. Repeat the procedure with the second anchor point.

Correcting color casts Pro

Like Levels, the Curve tool can be used to correct color casts. If they've been corrected already, using the individual Red, Green, Blue Channel mode of the Levels too, then there's likely no need to do so in the Curve tool.

If however only a combined RGB adjustment was made (i.e., setting the black and white clipping points), then the Curve tool is arguably the best tool. It can also be used to add color in the shadows, mid-tones or highlights. Alternatively, consider using the Color Balance tool instead.

When adjusting individual color channels, the Curve tool may be duplicated in the Inspector for each tab. Left click on the tool and select Add Tool > Curve. Repeat for each channel.

  1. Go to the Exposure Inspector.
  2. In the Curve panel, select individual Red, Green or Blue channels to adjust the color balance.    
  3. Click directly on the slope to add a control point in the tonal region that you want to adjust. (The upper-right of the slope adjusts highlights, and the center adjusts mid-tones. The bottom or lower-left adjusts the shadows.)
  4. Click on a control point and either drag or scroll up to add the chosen color, moving it down removes it.
  5. Click and drag the control point to left or right to lower or increase contrast in the chosen region.
  6. Add more points to the curve to adjust other areas. (To remove a control point, click and press delete/backspace or drag it off the curve.)
  7. As an option, you can also add points by selecting the Curve Point Picker and clicking on the area of your image that you want to adjust in the Viewer.

Apply a preset

The Curve tool has several built-in presets that are useful as a starting point.

  1. Go to the Curve tool and select the Manage Presets (hamburger) icon. The Presets menu opens.
  2. Select a preset from the list as a starting point.