In this Understand Photography quick tip, Joe Fitzpatrick explains what a histogram is and how to use it to get better exposed photos.
Reviewing a photograph on the camera’s LCD screen can be misleading since the brightness level of the LCD can be changed, causing the photo to look darker or brighter than it actually is. The brightness level of your surroundings can also influence how you perceive the brightness of photos you view on the LCD.
The typical histogram is a chart that divides the photo into 256 levels of brightness and shows what amount of the photo is at each level. Darkest tones are to the left and brightest to the right. Some histograms also show the amount of each primary color and each level of brightness. The histogram can be displayed on the camera’s LCD while reviewing a photo. Many mirrorless cameras also have the ability to show a histogram in the viewfinder or LCD in real time before you take a picture. Since the information in the histogram is not affected by the LCD’s brightness level or the brightness of your surroundings, it provides an accurate and consistent guide to exposure.
Most post-processing applications will also show a photo’s histogram. This can be useful when adjusting the photo’s overall exposure, highlights, shadows, whites and blacks. The shape of the histogram will vary widely, depending on the distribution of brightness in the image.
An image that is just pure black and pure white will have bars at each end and nothing in the middle. An image with an even distribution of brightness levels will have the 256 bars all at the same height. To capture all the detail in a scene, the histograms should not climb either end of the chart. If it climbs the left hand side, that means the darkest areas of the photo have no detail. If it climbs the right hand side, that means that the brightest areas of the photo have no detail.
We expect to see detail in bright areas, not so much in dark areas. If you can’t capture the whole range of brightness levels in an image, it is generally better to expose so that the important parts of the photo have detail.
Often, the histogram display is turned off by default on your camera and must be enabled in your camera’s menu. Consult your camera’s manual to see how to enable the histogram. By regularly checking your photos histograms, you will get a feel for when and how much exposure compensation to add to get perfect exposures.
Photographer, instructor and speaker.
Peggy Farren is an award winning, professional photographer, author, instructor and speaker. She’s been interviewed and featured on TV and in many national and local publications.