A Histogram is a graphical representation of the tonal values of your image. It illustrates how the pixels in a photo are distributed across brightness levels ranging from black (0% brightness) to white (100% brightness). Histograms are a useful way to judge the exposure and contrast of a photo and is widely used by advanced amateur and professional photographers.
Reading a Histogram
Histograms are read left to right. The left edge depicts pure black. As you progress to the right you move through the shadows, mid-tones, and highlights. The right edge depicts pure white. As you move the sliders for Exposure, Shadows, Highlights, Blacks, and Whites in the Tone adjustments, you’ll notice that the Histogram adjusts as tones are changed.
In addition to representing Luminance values, a Histogram also depicts Red, Green, and Blue color channels. By default, the luminance and color values are shown together in the RGB view. However, you can view each channel separately by clicking on the Histogram and choosing between RGB, Red, Green, Blue, and Luminance. These different views help spot color balance and other issues.
Highlight clipping is when detail is lost in the brightest areas of a photo. Shadow Clipping is when detail is lost in the darkest areas of a photo. The clipping warning, when activated, will overlay clipped highlight areas in red and clipped shadow areas in blue.
To activate or hide the clipping warning:
- Use the J key on your keyboard to show/hide both Highlight and Shadow clipping.
- View Highlight clipping by opening the Histogram and clicking on the light grey circle in the upper right of the Histogram.
- View Shadow clipping by opening the Histogram and clicking on the light grey circle in the upper left of the Histogram.