September '22

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G R A P H I C S - P R O. C O M S E P T E M B E R 2 0 2 2 • G R A P H I C S P R O 6 3 on your monitor to display the gamut of your printer – using at the very least, calibration software or better still, a colorimeter and a spectrophotometer to create an accurate custom ICC pro- file. Calibration is about producing an on-screen image based on the actual numerical RGB values of the pixels as displayed in the most accurate window possible. If there are color problems, they can be detected and corrected. COLORCAST One of the most common problems is the colorcast. A color- cast is an undesirable tint of a particular color that globally affects an image. It can be caused by reflected light from a nearby object or a specific light source. For example, many photos taken using fluorescent lighting tend to have a greenish colorcast. (Fig. 1) In film, the wrong timing or imbalanced chemical mixtures can cause colorcasts during development. Colorcasts can occur in old photographs due to the fading and discoloration of dyes, particu- larly under the action of ultraviolet light. is type of color dis- tortion is usually correctable on a scanned version of the image with image editing techniques. TIGHTROPE Ba lancing color is about wa lk ing the color tightrope. Specifically, adjusting an image to eliminate a blue colorcast can potentially add too much yellow. e same is true with eliminat- ing red that adds cyan, and green, which adds magenta. e point is that these colors exist within color ramps, where the strength of one color indicates the absence of another. "A colorcast is an undesirable tint of a particular color that globally affects an image." BALANCE POINT In this article, I'd like to cover three specific techniques that are surefire cures to eliminating pesky colorcasts and guarantee a balanced image every time. I'm demonstrating these features on Adobe Photoshop, but Adobe Lightroom and Corel Paintshop Pro have similar features. ere are several methods used to con- quer the colorcast conundrum and perfectly adjust complex color relationships, so let's start with the most obvious - Color Balance. Click the little scale shaped icon on the Adjustments panel to reveal the Color Balance controls in the Properties Panel (Fig. 2). is dialog box controls color in three different tonal ranges that are chosen from the tone menu: Highlights, Midtones and Shadows. It's generally best to start with the midtone range because it overlaps both shadows and highlights. Click the Preserve Luminosity check box to maintain the tonal balance of the image and affect only the color and not the darks and lights. Each of the three-color sliders represents the two color opposites I previously mentioned. By increasing the amount of a specific color by moving the slider toward its name, decreases its opposite. To increase the amount of a color in an image, drag a slider toward it. To decrease the amount of a color, drag the slider away from it. If you push any of the sliders too far the image can develop an intense tint (Fig. 3). e task is to find the perfect balance of colors within each tonal range. While adjusting with the sliders, you observe the changes on screen in real time. is is called the eyeball technique. It works, but it's not the most accurate. For maximum precision, you need to be able to read and understand numbers because numbers don't lie. The green slider has been pushed to the extreme producing an intense green tint. 3

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