Konica Minolta IV instruction manual Histogram corrections

Histogram corrections

The histogram indicates the distribution of pixels with specific brightness or color values in the image. Using the histogram can maximize the output of the image data. Changes made with the histogram are also displayed on the tone curve.

Input shadow slider		Input highlight slider
	Input gamma slider		Input shadow text box
				Input gamma text		box
					Input highlight text box

Output shadow slider				Output highlight text box
		highlight slider
	Output		Output shadow text box

The color histograms can be displayed with the channel list box or with keyboard shortcuts. While holding the control key (Windows) or command key (Macintosh), press 0 (zero) to display the RGB channel, 1 to display the red channel, 2 to display the green channel, or 3 to display the blue channel.

The histogram can be used to maximize the distribution of the pixels in the image. The highlight level, shadow level, and gamma can be set manually with the sliders or text boxes.

The gamma slider defines the mid-tones of the image. Dragging the gamma slider to the right will darken the image, and dragging it to the left will brighten it. Similar to the tone-curve correction described on page 62, the gamma slider allows the brightness of the image to be adjusted without loosing image information.

The input highlight slider sets the white level. As the slider is moved to the left, an apparent increase in contrast can be seen in the displayed image. All pixels to the right of the slider are set to 255 and any image detail they may contain will be lost. This can be an important tool for improving copy images of text on a white background. Uneven illumination, or faded or stained paper can be distracting when copying text or line art. By adjusting the white level, the imperfections of the white background can be eliminated leaving only the darker text visible.

64 ADVANCED IMAGE PROCESSING