How to Use a Histogram

Digital camera users have found a valuable tool for checking correct exposure on their images - the histogram. For owners of Single Lens Reflex (SLR) digital cameras and certain point-and-shoot digital cameras, the histogram provides an easy way to guarantee a well-exposed image.

To use the histogram, take a photograph with your camera. The light meter in your camera will be a good guide for correct exposure. This will be your initial exposure. Note the ISO setting, the f-stop aperture and shutter speed. Many cameras will record this information for you to easily retrieve later. Now consult the built-in histogram in your camera. How to access the histogram will vary between cameras. Check the camera's owner's manual for instructions.

It is important to view the histogram. Your image may appear properly exposed, dark or bright in the LCD screen. Do not depend on this viewing for determining the image's exposure captured by the camera. A bright LCD screen, for example, will make an image look brighter than reality. The histogram, on the other hand, graphs the image's real brightness and darkness.

Look through the LCD screen and view the histogram. This is how it appears in a Canon EOS digital camera.

The histogram is a graph that shows the range of light values in your image, ranging from dark/black on the left side to light/white on the right side. The middle areas are the gray values. The peaks represent the different colors in the image. The higher the peak, the more of that color there is in the image. The peaks and colors are not important. The range of where the image falls between light and dark are what is important for proper exposure. In the optimal image, the graph will be situated in the middle, not extending all the way to either side.

When an image falls to either of the edges, the light values at those edges will either be black or white. The edges do not contain gray so the more the image falls to either side the more image details will be lost by being either being completely black or completely white.

Looking at the graph, it will let you know if the image is too dark or too light. If it is too dark, the graph will be on the left side. The farther on the left, the more area of the image will be black. If the image is too bright, the graph will be on the right side. The farther on the right side, the more area of the image will be white. If your image is properly exposed the graph will be centered.

Correct your image by adjusting your exposure and retaking the image. Use the numbers from your initial exposure to help you adjust the exposure. To correct an image that falls to the left side (too dark), manually change the exposure settings by either increasing the ISO setting, lowering the shutter speed or using a wide open aperture f-stop such as f/1.8. To correct an image that falls to the right side (too bright), manually change the exposure setting by either decreasing the ISO setting, increasing the shutter speed or using a smaller aperture f-stop such as f/13.

Retake your image and check the histogram again. Repeat until you get the proper exposure.

While you can change the brightness with post-processing, you cannot retrieve parts of an image (black or white) where details have been totally lost. By changing your images while still taking the images with your camera you will get the better results and a great image from the beginning.

Remember to use your camera's histogram to get the best image exposure and decrease your post-processing time.

Shop at the Scrapbook.com Superstore for all your Scrapbooking Supplies!
Enjoy 5-Star service, HUGE selection and LOW prices!
Click here to start shopping!