特殊:Badtitle/NS100:Photos/CorrectColor

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1. title Correcting the Color of a Photo

If you have a discolored, tinted or poorly-exposed photo, you may be able to correct the photo by using one of the color correction tools available in the GIMP Image Editor.

Note: Color correction tools are available in other applications too. For example, in F-Spot Photo Manager, select a photo, press Edit -> Adjust Color... and adjust the sliders to correct the photo.

Brightness and Contrast

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If you have photos which are too bright or dark, or look washed-out, you can adjust the brightness and contrast.

• Press Tools -> Color Tools -> Brightness-Contrast...
• Adjust the sliders to change the Brightness and Contrast
• Press OK to apply your changes

See the GIMP Documentation for more information.

Tips

• Increasing the contrast too much will make noise/speckles in your photos look more obvious
• Increasing the contrast by a moderate amount should help make certain features stand out more

Color Balance

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Changing the color balance of a photo can help to fix problems such as poor exposure and color casts. After correcting the color balance, you will normally need to adjust other settings (such as brightness and contrast) to fully correct the photo.

• Press Tools -> Color Tools -> Color Balance...
• Identify which color is too prominent in the photo
• Find the color level slider which corresponds to that color
• Move that slider away from the color which you identified
• Press OK to apply your changes

You can change the color balance for different ranges of brightness in the photo:

• Shadows - darker areas of the photo, such as shadows and dark objects
• Midtones - the middle range of brightness
• Highlights - bright areas of the photo, such as white objects

Changing the color balance of the midtones will generally have the greatest impact on the overall color balance of the photo, but if you have a particularly dark or bright photo, you will probably want to make changes to the shadows or highlights first.

See the GIMP Documentation for more information.

Example

Take a photo which is very blue, possibly due to using the wrong exposure setting on your camera:

• Move the first slider towards Red. This will reduce the balance of Cyan in the photo
• Move the third slider a little towards Yellow to reduce the other blues in the photo
• Optionally, move the second slider towards Magenta to enhance the red colors in the photo
• Adjust the brightness and contrast

Hue, Lightness and Saturation

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If you have a photo in which certain colors are too bright or too dull, you can change how prominent a color is by altering its hue, saturation and lightness.

• Press Tools -> Color Tools -> Hue-Saturation...
• Select a color to modify, or select Master to modify all colors at once
• Adjust the sliders as appropriate:
  • Hue - Changes the color of the original colors in the photo. If you have one color selected, it will replace that color with a new color.
  • Lightness - How bright the selected color looks. This can lead to patchy areas on photos if used with single colors, so is normally best used on the photo as a whole (i.e. with Master selected).
  • Saturation - How 'intense' a color looks. Increasing the saturation will result in a color appearing brighter and more intense, whereas reducing the saturation will dull the color and make it look more grey.
• Press OK to apply your changes

See the GIMP Documentation for more information.

Tips

• Making large adjustments to a single color can cause 'patches' to appear on the photo. Avoid making large adjustments if possible.
• If you changed a color but would like to undo your changes, select that color and press Reset color.
• Changing the Hue for all colors (i.e. with Master selected) can lead to some interesting artistic effects (blue grass, red skies and so on).
• If you have a color which appears too bright on the photo (e.g. someone wearing a bright red jacket in a mostly green photo), decrease the saturation of that color to reduce its impact.

Levels

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The Levels tool lets you adjust the 'balance' of colors in a picture (see also the Color Balance tool). In particular, you can adjust the white balance of a photo to make the colors of objects seem more realistic/true to life.

See Wikipedia for more information on white balance.

Automatically adjusting the white balance

The Levels tool can automatically adjust the white balance of your photo by guessing which parts of the photo are pure black and pure white.

• Press Tools -> Color Tools -> Levels...
• Under All Channels, press the Auto button. The white balance will change
• Press OK to apply your changes

Manually adjusting the white balance

For more control over the white balance of a photo, follow the instructions below:

• Press Tools -> Color Tools -> Levels...
• Under All Channels, press the white point button (far right)
• Click on a spot on the photo which is as close to a pure white color as possible (such as a white cloud or white paper). The white balance will change
• Under All Channels, press the black point button (immediately to the right of the Auto button)
• Click on a spot on the photo which is as close to a pure black as possible (such as black shoes or a dark shadow). The white balance will change
• Press OK to apply your changes

See the GIMP Documentation for more information.

Color Curves

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The Color Curves tool lets you fine-tune the brightness of colors across the whole range of colors in the photo. It is useful for making photos look more vivid or 'moody'.

• Press Tools -> Color Tools -> Curves...
• Select a color channel to modify (Value, Red, Green or Blue). Changing the Value channel will change all color channels at once
• Click on the line on the graph to add a new node
• Drag the node around to change how much a given part of the color range is changed
  • An indication of the part of the color range that a node is in can be seen on the thin strip just below the graph
  • Moving the node up will make that part of the range lighter
  • Moving the node down will make that part of the range darker
  • Moving the node across will stretch or compress part of the range, increasing or decreasing its impact on the photo
• Press OK to apply your changes

See the GIMP Documentation for more information.

Tips

• Moving the curve down slightly in the shadows (the left of the graph) and up slightly in the highlights (the right of the graph) can often improve photos. This simply makes dark tones darker and light tones lighter, making the photo look a little more vivid.
• If you click on the photo while the color curves window is selected, the color of the point which you clicked on will be indicated on the color curve graph.
• Instead of moving points around on a smooth curve, you can draw the curve yourself (which can lead to some interesting effects). Press the Freehand button under Curve Type to switch to freehand curve drawing.

Colorise

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The Colorise tool allows you to apply a tint to a photo.

• Press Tools -> Color Tools -> Colorise...
• Adjust the sliders to obtain the desired effect (see below)
• Press OK to apply the effect

See the GIMP Documentation for more information.

Options

The following options are available:

• Hue - Changes the color of the tint.
• Saturation - Changes how 'vivid' the tint is. A high saturation will give a very bright color, a low saturation will give quite a muted color and zero saturation will appear grey.
• Lightness - Changes how light the photo is. To make the photo look dark, use a negative value. To make it look bright, choose a positive value.

Useful settings

<tablestyle="text-align:center" rowstyle="background:#DBBA75"> Tint

Hue

Saturation

Lightness

Sepia tint

50

60

0

Rose tint

0

50

0

Sky (blue) tint

216

64

0

More Information

• Enhancing photographs with GIMP