The Colour Photography Field Guide by Michael Freeman

Author:Michael Freeman
Language: eng
Format: epub
Publisher: Ilex Press/ Ivy Press
Published: 2013-04-15T00:00:00+00:00

AFTER

After applying the settings shown to the left, the tones have been stretched across the histogram, for a more contrasty image.

The process known as optimization is designed to make an image appear at its best by making the fullest use of the gamut of the monitor and printer. The first step is to spread the range of tones and colors captured as widely as possible over the 8-bit scale from black (0) to white (255). This is known as setting the black point and white point, and there is a choice of techniques. In Photoshop, the starting point is Levels. There are three sliders below the histogram, one each for black point (left), white point (right) and mid-point (center). Drag the black-point slider in from the left until it reaches the first group of pixels in the histogram. These are the darkest pixels in the image, and doing this will make them black. Then do the equivalent with the white-point slider. Click OK. To check the result, reopen the Levels dialog and you will now see that the histogram has been stretched to fill the full scale. A useful check when doing this is to hold down the Alt/Option key as you drag the sliders. With the black-point slider the image on screen will be pure white until you reach the first pixels—it will indicate at what point you begin to clip the shadows. With the white-point slider the same key has a similar effect, except that the base color on screen is black.

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