Use this menu to select the Color Space of the source image, if it is known. This can make the correction more accurate since the tool will be able to take the natural gamma of the color space into account as part of the correction. If the color space that the image uses is unknown, leave this menu at its default value.

The white balance tool can operate using one of two methods, a Custom method and a color Temperature method.

The Custom method requires the selection of a pixel from the scene that should have been pure grey.

The tool uses this information to calculate the color correction required to convert the pixel so that it actually is grey. When that correction is applied to the entire image, it generally white balances the entire shot.

The color Temperature method requires that the actual color temperature of the shot be specified.

This checkbox locks the Black, Mid and White points together so that the entire image is affected equally. Unchecking the control will provide individual controls for white balancing each range separately. This control affects both methods equally.

These controls only appear if the Custom method is selected. They are used to select a color from a pixel in the source image. The white balance tool will color correct the image so that the selected color is transformed to the color set in the Result color picker below. Generally, this is grey. A color that is supposed to be pure grey but is not truly grey for one reason or another should be selected.

If the Lock Black/Mid/White checkbox is deselected, different references can be selected for each color range.

For example, try to select a pixel for the black and white references that is not clipped in any of the color channels. In the high end, an example would be a pixel that is light pink with values of 255, 240, 240. The pixel is saturated/clipped in the red, even though the colour is not white. Similarly, a really dark blue-grey pixel might be 0, 2, 10. It is clipped in Red as well, even though it is not black.

Neither example would be a good choice as a reference pixel because there would not be enough headroom left for the white balance tool.

These controls only appears if the Custom method is selected. They are used to select the color to which the tool will balance the reference color. This generally defaults to pure, midrange grey.

If the Lock Black/Mid/White checkbox is deselected, different results can be selected for each color range.

Use this control to set the color Temperature of the source image. If the Lock Black / Mid / White checkbox is deselected, different references can be selected for each color range.

Use this control to set the target color temperature for the image. If the Lock Black / Mid / White checkbox is deselected, different results can be selected for each color range.

This checkbox selects whether the tool will take the gamma of the image into account when applying the correction, using the default gamma of the color space selected in the menu at the top of the tab.

The Ranges Tab contains the controls used to specify which pixels in an image are considered to be shadows and which are considered to be highlights. The midrange is always calculated as any pixels not already included in either the shadows or the highlights.

Spline Display

The extent of the ranges is selected by manipulating the spline handles. There are four spline points, each with one Bezier handle. The two handles at the top represent the start of the shadow and highlight ranges, whereas the two at the bottom represent the end of the range. The Bezier handles are used to control the falloff.

The midtones range has no specific controls since its range is understood to be the space between the shadow and the highlight ranges.

The X and Y text controls below the Spline Display can be used to enter precise positions for the selected Bezier point or handle.

Preset Simple/Smooth Ranges

These two buttons can be used to return the spline ranges to either Smooth (default) or Simple (linear) settings.