Sign & Digital Graphics

March '20

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6 6 • M A R C H 2 0 2 0 • S I G N & D I G I T A L G R A P H I C S is composed of lines that show the rela- tive number and distribution of tonal values within an image. The lines may appear to look like a mountain range, that's because they are so close together on the graph. In the Panel Options menu select Expanded View and All Channels View and Show Channels in Color. Also click the tri- angle with the exclamation point to dis- play the uncached histogram. (Figure 3). The left side of the histogram represents dark pixels with low values called shadows. The right side of the graph represents light pixels or highlights. The central areas of the graph represent the image's midtones. When an image is deficient in contrast the left and right sides of the graph are void of lines. Correcting Contrast The easiest method for improving contrast is to apply a quick Levels adjust- ment. First, click on the Levels icon in 3 Click the triangle with the exclamation point to display the uncached histogram. 4a 4a Drag the shadow and highlight sliders until they touch the lines of the histo- gram to improve the contrast. the Adjustments panel to generate a Levels adjustment layer. I recommend that you always use adjustment layers for these types of corrections so that you can later refine your adjustments if necessary. The Properties panel displays the Levels control that also displays a histogram. The Levels properties panel enables you to reconfigure the graph, and therefore the image's brightness levels by dragging Shadow, Midtone and Highlight sliders. Brighter Brights, Darker Darks Poor contrast is a result of lighter colors not being light enough and the darker colors not being dark enough. Pictures with poor contrast have a gray- 4b 4b 5 The Curves Properties panel. ish tinge because the brightness values of the image are clustered in the center of the histogram. What you want is brighter highlights and darker shadows and this can be achieved by extending the range of the graph. Drag the right highlight slider to the left until it touches the right side of the histogram's lines. Conversely, drag the left shadow slider to the right until it touches the left side of the his- togram's lines. (Figure 4A) You can also adjust the overall brightness by drag- ging the midtone slider. Voilà! Contrast improved! (Figure 4B) This is the quickest fix for adjust- ing contrast. There are more detailed and sophisticated methods that map the images brightness to specific white and black points, or adjustments to targeted ranges of color by applying a dedicated curves adjustment and these techniques require broader knowledge of the nature of digital color. The method described above however is fast and simple and almost always provides a vast improve- ment to image contrast. Color Deficiencies More times than not, a contrast adjustment isn't enough. If the contrast has been adjusted and the colors seem to be a bit out-of-whack then a targeted color adjustment will correct the color values and make the image "pop". This fix requires a slightly more complex Curves adjustment.

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