Levels Adjustment

Find out how to use the Levels tool to control the tonal distribution and alter the contrast. The Levels tool can also be used to correct color casts in the individual color channels.

An overview of the Levels tool

The Levels tool in Capture One, when in the combined RGB mode is used to adjust the contrast and brightness in an image. This achieved by modifying the tonal values of your image, typically expanding the tonal range shown in the Levels’ histogram. It is especially useful with low-contrast images such as those taken in flat lighting or heavily-diffused light, such as hazy or foggy daylight that contain compressed tonal values with few if any clipped areas. However it will depend on your creative intent.

Selecting an Auto Levels in the combined RGB Channel mode, Capture One will attempt to set the shadow and highlight sliders to either side of the histogram, thereby increasing contrast and altering the brightness. Some small number of pixels are allowed to go to pure black or white, such as specular highlights, without substantially affecting the overall contrast.

Adjusting the shadow and highlight sliders maps the pixel values at those points to the selected output values (shown above the histogram). If the output sliders or output values are left to the defaults, the points will be mapped to 0 and 255. For example, adjusting the input shadow slider to level 8 maps all pixels and below that value to 0 (pure black). If the highlight slider is moved to left at level 250 it will map all at those pixels at that level and above to level 255 (pure white).

These end-points represent the levels at which both shadow and highlight pixels start to clip and lose detail (known as the black and white 'clipping' points, respectively). A middle-slider is provided to adjust the adjusts brightness, or gamma, of the mid-tones. Moving it to the right compresses the shadows and lightens the highlights, while moving it to the left compresses the highlights and lightens the shadows. While the remaining RGB values are re-distributed to avoid color shifts, the combined RGB mode will not correct any inherent color in-balance.

The Levels tool can, however, also be used to adjust the color balance of the image. If a color shift is present you can adjust the Levels using the individual Red, Green and Blue Channel mode instead. Adjusting each histogram end-point manually is possible, however, it is quicker to switch channel mode and apply an Auto Levels on the individual channels. This often provides a very realistic-looking result. A shortcut to the application preferences is provided from the Levels tool’s action menu.

Setting Levels mode

The Levels tool has two channel modes (combined RGB, and individual Red, Green and Blue) which you can switch between manually using the tabs. However, to apply auto levels correction, or use the shadow and highlight pickers for each, you must select the appropriate mode from the application preferences.

  1. Select an image from the Browser.
  2. Go to the Exposure Inspector and head to the Levels tool.
  3. From the Level’s tool title bar, click on the Action button (… icon), and select Preferences…
  4. Alternatively, from the main menu, select Capture One/Edit (macOS/Windows) > Preferences. The preferences dialog window opens.
  5. From the Levels Tool area select the appropriate Channel Mode from the fly-out menu.

Auto adjust brightness and increase contrast Pro

When set to the default combined RGB Channel mode, the Auto option automatically sets black and white points that widens the tonal range thus increasing contrast and modifying the overall brightness.

The Auto option will provide an good initial result, but further fine-tuning of the input sliders is usually necessary, depending on your creative intent. Select the shadow point (left), mid-tone (middle), or highlight (right) point sliders underneath the histogram and drag to the left to lighten or to the right to darken the image.

When making adjustments, toggle on and off the highlight warning option in the tool-bar while assessing the image for clipping, as the red warning mask will inhibit adjustment.

In most cases, adjustment will be based on the final destination whether in print or the web. If the latter, then it is usually a case of adjusting brightness using the mid-tone slider.

With print, close attention is necessary when dealing with highlight detail, though be aware some print output profiles attempt to lighten the shadows. That is also the case when BPC is enabled when printing directly from Capture One. When assigning values, the shadow picker should be used. For more information, see below.

  1. Select an image from the Browser.
  2. Go to the Exposure Inspector and head to the Levels tool.
  3. Select RGB and verify the tool is in the Auto RGB Channel mode by the inclusion of shadow and highlight pickers (eye-droppers) in that tab.
  4. From the Level’s tool title bar, click on the A icon. New black and white points are set under the histogram, and the histogram is adjusted (usually expanded). The image in the Viewer will display more even brightness and an increase contrast.
  5. Optional. Adjust mid-tone (gamma) brightness slider to suit (left to lighten, right to darken), and fine-tune black and white point sliders to reduce clipping if present.

Manual adjustment of brightness and contrast

Manual adjustment of the Levels tool to improve contrast and brightness is possible instead of an Auto Levels correction. Alternatively, adjustment can be made afterwards as part of refining the settings based on the intended output or creative intent. Adjustment of the combined RGB Levels is not only confined to color but it is especially useful for improving the tonality of black and white images.

First set the black point slider to lessen clipping, or blocking, then the white-point slider while checking on-screen for clipping of highlights (see below for more details). Once selected, adjust the middle slider to the left to lighten or to the right to darken the image without clipping either end-point. In most cases this will be subjective, depending on the image content. 

If the final destination is in print and the image contains nuanced detail in the highlights that you would like to retain, adjust the highlight clipping point slider to just less than pure white at 255 (e.g., 250), making the image slightly darker.

If the image contains specular highlights (highlights without any detail), it is common practice to leave these to clip and adopt the same hue of the paper.

  1. Select an image and go to the Levels tool, and select RGB (combined channel mode).
  2. Optional. Click on the tool’s action menu and select Preferences… The application preferences opens. Add a check mark to Enable Shadow Warning.
  3. Select Show Exposure Warnings from the main tool bar (cmd/ctrl-E).
  4. Set the black point in the image by moving the left end-point slider beneath the histogram to the point where the histogram begins to rise on the left (i.e. to define the darkest shadow). Stop when the blue-colored shadow warning is displayed in areas of the image that are being clipped. Zoom into the shadow areas to confirm.
  5. Adjust the white point slider to the point where the histogram rises on the right (i.e., the brightest highlight). Areas denoting the on-screen highlight warning should be minimal, with the exception of specular highlights (light sources or reflections) which can be left to clip.
  6. Optional. Adjust High Dynamic Range tool’s Highlight slider to the right to reduce clipping.
  7. Modify brightness with the middle (gamma) slider, moving to the left to lighten or to the right to darken. Adjust to individual taste.

Adjust brightness and contrast using shadow and highlight pickers (optional) Pro

The shadow and highlight pickers can be used to select the black and white points in the Viewer. Although it can be difficult for inexperienced users to decide on the correct areas to select, you can use the Levels’ orange histogram marker derived from the cursor tool’s position to target the end points.

The pickers can also be used to select shadow or highlight points in the combined RGB channel mode and assign target values to specific parts of the image to new output values.

Although you can set the output values directly from the Levels panel, using the provided text boxes, the values can be set from the application preferences when they're required on a permanent basis.

To use the pickers to set shadow and highlight color, you must switch mode to the individual Red, Green and Blue channel mode from the application preferences. If you use the pickers be aware that they undo previous auto or manual adjustments.

The following description relates to setting shadow and highlight points using the combined RGB mode.

  1. (Optional). Go the application preferences and select the Exposure tab. Enable Pick Target Levels and adjust the sliders to set the required values.
  2. Go to the Exposure Inspector.
  3. From the Levels tool, select combined RGB mode to set shadow and highlight points.
  4. Select the Shadow Picker and click on an area of your image in the Viewer that's the darkest shadow with detail. You may need to zoom into the image.
  5. Select the Highlight Picker and click on an area that is the brightest highlight with detail in your image.
  6. (Optional, depending on intention.) Adjust the middle slider to the left to lighten or to the right to darken mid-tones, as desired.

Auto correct color casts and contrast

Before the Auto correction of color can take place, the Levels tool must be set to the indvidual Red, Green and Blue Channel mode.

In many cases, the Auto Levels correction of color yeilds a more pleasing result than the Auto levels in the combined RGB mode.

The channel mode is changed from the application preferences - a shortcut is provided from the tool’s Action menu button (… icon).

The levels tool automatically corrects color casts, and sets histogram end points, however, manual adjustment of the color balance in each color channel is also possible.

Each slider modifies the shadows, mid-tones and highlights, respectively, by adding or removing color. For example, moving the shadow slider in the Blue channel to the left adds blue to the shadows. Moving it to the right removes blue, revealing a green tint.

While Levels is useful for basic corrections, for precise control consider using the more intuitive Color Balance tool or Curves, if familiar with it.

  1. Select an image from the Browser.
  2. Go to the Exposure Inspector and head to the Levels tool.
  3. Confirm the Levels tool is set to the individual channel mode. (See above for details.)
  4. From the Level’s tool title bar, click on the A icon. The individual channels are re-mapped to new values and histograms are adjusted, if within the 0 to 255 levels. Color casts will be corrected and the image will display increased contrast.
  5. Optional (advanced). Adjust color tone using mid-tone, shadow and highlight sliders. For example to add red, click on the Red channel tab and adjust individual sliders to suit.

Adjust output levels Pro

Output levels can be set manually by adjusting the sliders at the top of the histogram, or by entering values in the boxes directly above. Input levels are re-mapped to those new output values.

When used this way the Levels tool can be used to compress the tonal range and reduce the contrast in the combined RGB channel mode, giving the image an offset look in the shadows for example, or using the individual color channels to introduce color shifts in different tonal regions. 

Output values can be set before adjusting input values or afterwards, depending on your intent. For example, when reducing contrast or adding a slight offset, it is usually performed after setting the input values. 

  1. Go to the Exposure Inspector.
  2. From the Levels tool, select the RGB mode 
  3. Select A or adjust by pulling the shadow and highlight point sliders until they’re just touching either ends of the histogram.     
  4. Check Highlight and Shadow warnings to identify any clipped pixels, and adjust as needed.
  5. Adjust the middle slider to lighten or darken mid-tones as desired. 
  6. Adjust upper shadow and/or highlight sliders or add values in the text boxes to reduce output values, while observing the effect in the Viewer.
  7. Optional. Select the individual Red, Green or Blue tabs to access and adjust separate color channels and modify the color balance using the output sliders.
  8. Levels settings may be saved as a preset and applied to multiple images.

Modify Auto Levels clipping thresholds

Capture One’s default settings for Auto Levels' allow 0.1% of the pixels to clip at the black and white points. This prevents those few pixels from adversely affecting the rest of the image in terms of contrast and tone.

The range for each is adjustable between 0.00 to 10% but in most cases it is unlikely that a value as high as 1% would be adopted, even when taking a moderately large area of specular highlights into account.

Before deciding on the modified values, however, if the final destination is in print, it is recommended that test prints are made to determine the individual characteristics of your printer, including specific paper and inks.

  1. Select an image from the Browser.
  2. Go to the Exposure Inspector and head to the Levels tool.
  3. From the Level’s tool title bar, click on the Action button (… icon), and select Preferences…
  4. Alternatively, from the main menu, select Capture One/Edit (macOS/Windows) > Preferences. The preferences dialog window opens.
  5. From the Levels Tool area go the Auto Levels Clipping Thresholds section and add values to the relevant Shadows and Highlights text boxes. (Note you can only type in values).
  6. Once the values are set, they’re saved. As there’s no need to close and re-open Capture One you can return to making adjustments after closing the preferences dialog.

Preview exposure warnings

You can preview clipping in the highlight and shadows while working on various tools in Capture One that alter the exposure. The warnings are an essential aid in determining when image detail is lost during adjustment.

The feature is not restricted to working with the Levels tool alone, but it is particularly useful when manually adjusting the shadow and highlight sliders to the clipping points. Clipped points are either pure black or pure white, and lack any image detail.

The Exposure Warning indicator is located in the right-hand group of the main tool bar. The preview displays a red colored mask in the highlight areas, warning that at least one color channel (red, green or blue) is clipping and image detail may be lost as result. Check the histogram in the Levels tool to see which channel is clipping; it will spike against the wall.

The default setting for the shadow warning is disabled. However, this can be enabled from the application preferences (Capture One/Edit (macOS/Windows) > Preferences… > Exposure tab > Exposure Warning > Enable Shadow Warning. When enabled, the clipped shadow areas are displayed in blue.

The clipping thresholds and the color for each of the masks can also be modified from the application preferences. Click on the color window and select from the swatch.

Note the default highlight clipping threshold is below 255 (pure white) at 250, to allow a small number of pixels to clip. In most cases, the sliders can be left to the defaults.