GRAPHICS PRO

November '20

Issue link: https://nbm.uberflip.com/i/1300666

Contents of this Issue

Navigation

Page 62 of 118

5 8 G R A P H I C S P R O N O V E M B E R 2 0 2 0 G R A P H I C S - P R O. C O M S I G N A G E & P R I N T I N G T H E D I G I T A L E Y E Select the Histogram panel in the Win- dow menu and observe the graph. A his- togram is a graph composed of lines that show the relative distribution of tonal values within an image. The more lines the graph has, the more tonal values are present within the image. The height of a line represents the relative quantity of pixels of a particular brightness. The taller the line, the more pixels of a particular brightness the image contains. The histogram looks like a mountain range on some images, because a total of 256 tonal values can be represented at one time, and the lines are so close together that they create a shape (Figure 8). The dark pixels, or shadows, are represented on the left side of the graph; the light pixels, or highlights, are on the right. The midtone ranges are in the central areas of the graph. Furthermore, the Histogram panel can be expanded to display indi- vidual color channel information. CONTRAST DEFICIENCIES The histogram can tell us about the tonal characteristics of an entire image or a se- lected region; therefore, histograms can indicate deficiencies in color and contrast. For example, a histogram devoid of lines on both the left and right sides of the graph indicates that most of the pixels are in the midtone range and are devoid of highlights and shadows. Histograms like this indicate poor contrast, as you can see in Figure 9, and require a tonal adjust- ment to restore the dark and light areas. ESSENTIALS Measuring color is critical to producing vibrant, clean images that have impact. It is essential to measure color when performing color corrections like levels, curves, or color balance adjustments. The human eye is an accurate device for see- ing color, but unfortunately the brain im- poses its subjective opinions, which can be inaccurate. The one real rea- son to measure color is that num- bers don't lie. What you read in the Info or Histogram panel is the indisputable truth and that's the best possible place to begin your corrections. GP STEPHEN ROMANIELLO is an artist and educator, teaching digital art at Pima Community College in Tucson, Arizona, for over 29 years. He is a certified instruc- tor in Adobe Photoshop and the author of several books on the creative use of digital graphics software. Steve is the founder of GlobalEye Systems, a company that offers training and consulting in digital graphics software and creative imaging. Figure 8 (left). The histogram looks like a mountain range because all 256 tonal values are represented. The lines are so close together that they create a shape. Figure 9 (below). A histogram devoid of lines on both the left and right sides of the graph indicates that most of the pixels are in the midtone range. The image lacks highlights and shadows and is of poor contrast. dow menu and observe the graph. A his dow menu and observe the graph. A his togram is a graph composed of lines that togram is a graph composed of lines that show the relative distribution of tonal show the relative distribution of tonal values within an image. The more lines values within an image. The more lines values within an image. The more lines the graph has, the more tonal values are present within the image. The height of a line represents the relative quantity of pixels of a particular brightness. The taller the line, the more pixels of a particular brightness the image contains. range on some images, because a total of 256 tonal values can be represented at one time, and the lines are so close together that they create a shape ( dark pixels, or shadows, are represented on the left side of the graph; the light pixels, or highlights, are on the right. The Figure 8 (left). range because all 256 tonal values are represented. The lines are so close together that they create a shape. Figure 9 (below). the left and right sides of the graph indicates that most of the pixels are in the midtone range. The image lacks highlights and shadows and is of poor contrast.

Articles in this issue

view archives of GRAPHICS PRO - November '20