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Exploring adjustment filters
Corel PHOTO-PAINT provides you with many filters to adjust the color and tone of images. Some of these filters offer the same controls that can be found in the Image Adjustment Lab. However, most of these filters are advanced tools that give you greater control over the image correction process or let you change colors for specific effects. Many of these filters are also preset lens types. For more information about using lenses, see “Working with lenses.”
The Auto adjust filter equalizes the shadows, midtones, and highlights in an image by automatically redistributing the significant pixel values throughout the tonal range. This adjustment is performed on each color channel of the image, resulting in changes to the color and tone of the image.
The Contrast enhancement filter lets you adjust the tone, color, and contrast of an image while preserving shadow and highlight detail that is lost when you adjust the brightness, contrast, and intensity of an image. An interactive histogram lets you shift or compress brightness values to printable limits. The histogram can also be adjusted by sampling values from the image.
The Local equalization filter lets you enhance the contrast near image edges and reveals details in both light and dark regions. The filter uses neighboring pixels to create a stylized effect.
The Histogram equalization filter lets you view the tonal range of an image and redistribute the balance of shadows, midtones, and highlights in the composite channel or in individual color channels according to a preset histogram model.
The Sample/Target balance filter lets you shift the tonal range of an image by sampling specific image areas. You can take samples from shadow, midtone, and highlight areas, and set target tonal values by choosing colors from a color model. For example, if you want to increase the tonal range, you can sample a shadow area to set the target color to black, and then sample a highlighted area to set the target color to white. You can also shift the tonal range for a specific color channel. The tonal range is displayed as a histogram.
The Tone curve filter lets you perform color and tonal corrections by adjusting either individual color channels or the composite channel (all channels combined). Individual pixel values are plotted along a tone curve that appears in a graph and represents the balance between shadows (bottom of graph), midtones (middle of graph), and highlights (top of graph). The x-axis of the graph represents the tonal values of the original image; the y-axis of the graph represents the adjusted tonal values.
The tone curve shows the balance between the shadows, midtones, and highlights of an image. The original (x) and adjusted (y) pixel values are displayed side by side when you drag the tone curve. This example shows a small adjustment to the tonal range, in which pixel values of 152 are replaced with pixel values of 141.
You can fix problem areas by adding nodes to the tone curve and dragging the curve. If you want to adjust specific areas in an image, you can use the Eyedropper tool and select the areas in the image window. You can then drag the nodes that appear on the tone curve to achieve the effect you want.
Left to right: Original image; the image with adjusted tonal range.
The histogram lets you view the adjusted tonal range and evaluate the results. For more information about histograms, see “Using histograms.”
To fine-tune your adjustments, you can choose a curve style from the Style list box. For example, you can redraw the curve by using freehand lines or straight line segments.
You can adjust the color and tone of an image by applying a preset. To access a preset, click the Open button to the right of the Presets box. You can also save tone settings as presets to use with other images.
In addition, you can equalize the tonal range of an image by clicking Auto balance tone. To specify the outlying pixels (clipped pixels) at each end of the tonal range, you can click Settings and type values in the Auto-adjust range dialog box.
Auto Balance tone
The Auto balance tone filter equalizes shadows, midtones, and highlights in an image by automatically redistributing the pixel values throughout the tonal range.
The Brightness/Contrast/Intensity filter lets you change the brightness, contrast, and intensity of an image. You can shift pixel values up or down the tonal range. Adjusting the brightness lightens or darkens all colors equally. Contrast and intensity usually work together because increasing the contrast can wash out detail in shadows and highlights; however, increasing the intensity can restore this detail.
The Gamma filter lets you reveal detail in a low-contrast image without significantly affecting the shadows or highlights. With this filter, the tonal correction of the image is based on the perception of tones relative to the surrounding area. For example, if you place a circle filled with 10 percent gray on a black background, and an identical gray circle on a white background, the circle surrounded by black appears lighter than the circle surrounded by white, even though the brightness values are identical. The Gamma filter affects all image values, but it is curve-based; consequently, changes are weighted toward the midtones.
The Desaturate filter creates a grayscale image without changing the color mode. For example, you can apply the Desaturate filter to a color photo to create a black-and-white photo effect. It automatically reduces the saturation of each color to zero, removes the hue component, and converts each color to its grayscale equivalent.
The Hue/Saturation/Lightness filter lets you change the hue, saturation, and lightness values of an image or channel. Hue represents color; saturation represents color depth or richness; and lightness represents the overall percentage of white in an image. Color ribbons display the shift in hue.
The Selective color filter lets you change a color by changing the percentage of the component process colors (CMYK values) in a color spectrum (reds, yellows, greens, cyans, blues, and magentas). This filter also lets you add process color to the grayscale tonal component of an image. Selective color modifications increase and decrease the percentage of cyan, magenta, yellow, and black pixels that make up each primary color in the color spectrum. For example, decreasing the percentage of magenta in the reds spectrum results in a color shift toward yellow. Conversely, increasing the percentage of magenta in the reds spectrum causes a color shift toward magenta and an overall increase in red. The extent of color modification depends on the adjustment percentage method you choose.
You can mix color channels to balance the colors of an image. For example, if an image has too much red, you can adjust the red channel in an RGB image to improve image quality. For more information about mixing channels, see “Working with color channels.”
The Replace colors filter lets you replace one image color with another color. A color mask is created to define the color to be replaced. Depending on the range you set, you can replace one color or shift an entire image from one color range to another. You can set the hue, saturation, and lightness for the new color.
The Color balance filter lets you adjust the color balance of an image by shifting the colors between complementary pairs of the primary RGB color values and secondary CMY color values. This method is useful for correcting color casts. For example, if you want to tone down the red in a photo, you can shift the color values from red to cyan. You can also change the hue values to change the colors used in an image.
The Color hue filter lets you change the hue of an image by clicking sample thumbnails. For example, you can remove a yellow cast from an image by clicking a thumbnail that adds blue. The intensity of the effect increases by a specified amount each time you click the thumbnail. The thumbnails also let you preview the color hue adjustment.
The Color tone filter lets you change the brightness, saturation, and contrast of colors by clicking sample thumbnails. The intensity of the effect increases by a specified amount each time you click the thumbnail. The thumbnails also let you preview the color tone adjustment.