What term describes a graphical representation of a digital image?

• A. Histogram
• B. Brightness map
• C. Pixel map
• D. Tone curve

Answer: (A)

The main idea being tested is how the tonal content of a digital image is summarized in a single graphic. A histogram exactly shows this by plotting how many pixels in the image fall at each brightness level, from dark on the left to light on the right. This gives a quick sense of exposure and contrast and can reveal clipping at the shadows or highlights. The other terms aren’t standard graphs of pixel brightness distributions: a brightness map isn’t a widely used term for this kind of chart, a pixel map refers more to locations of pixels than their tonal values, and a tone curve is an editing tool that maps input brightness to output brightness rather than a display of the image’s current distribution. So the graphical representation of the image’s brightness distribution is the histogram.