What is a histogram?

What is a Histogram?

By Derek Leath

A camera histogram is a graphical representation of the tonal distribution in an image captured by a camera. It displays the number of pixels at each tonal value, from dark to light, allowing photographers to analyze the exposure and overall brightness of the image.

By examining the camera histogram, photographers can evaluate the exposure of an image. A well-exposed image typically has a histogram that is spread out across the tonal range, without any areas excessively concentrated on one end or the other. If the histogram is skewed towards the left side, it indicates underexposure (too dark), while a skew towards the right suggests overexposure (too bright).

This image shows an underexposed photograph (too dark).

As you can see, most of the image lacks any sort of bright detail. Histogram clearly shows a strong shift to the left side with most tones in the shadow range, and some are even clipped (completely black).

In this image, there are barely any tones at the extreme left-side of the histogram, where blacks are shown, which means there is no detail lost in shadows. It is sufficiently dark, yet still bears enough detail.

This image is overexposed (too light). Many tones are very bright and there are basically no darker tones. A large portion of the image is blown-out (completely white) and bears no detail at all. As you can see, the histogram confirms that the image is much too bright – it is shifted strongly to the right.

Photographers can use the histogram to make exposure adjustments while shooting. By analyzing the histogram, they can determine if the image is properly exposed or if adjustments need to be made to the camera settings, such as aperture, shutter speed, or ISO, to achieve a better exposure.

Histograms are available in many digital cameras, and they can also be viewed and analyzed during post-processing. Histograms are valuable tools for understanding and adjusting the tonal distribution in an image and ensuring proper exposure.

In post-processing, histograms are helpful for fine-tuning the tonal range of an image. By adjusting the brightness, contrast, or levels based on the histogram, you can enhance the overall tonal balance and improve the visual impact of the image.

Histograms are a valuable tool for photographers to assess exposure, adjust settings, and make informed decisions about capturing and processing images.

About the Author:

Derek has been a photographer since his parents bought him a Kodak film camera at age 9, (which he still has by the way). Derek moved on to 35mm cameras in the mid 70’s.

He was one of the newspaper and yearbook photographers at Ladue High School and won the Kodak Scholastic Award twice for the state of Missouri in 1980. He built a darkroom in the basement and learned to process and print.

Later he became a professional photographer, after working as an assistant for several top photographers in St. Louis. He started his own photography company DL Images and went on the study graphic design and large format printing.

He has one of the largest film camera collections in St. Louis and continues to shoot film as well as digital cameras. Most of his work is black and white.

Derek recently joined the Photo Pros because he loves working with people and enjoys helping them with their photography skills. Derek was a previous Creve Coeur Camera employee and he continue to teach camera basics, film photography and more at the Photo Pros.

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