What is Gamma and How is it Used in Photography?

Why You Need to Calibrate Your Monitor

A photographer looks at his photos.
A photographer looks at his photos. JGI/Tom Grill/Getty Images

Gamma is a nonlinear operation used to code and decode brightness values in still and moving imagery. It is used to define how the numerical value of a pixel relates to its actual brightness.

While gamma is extremely difficult to understand in its entirety, it is important for digital photographers to understand how it applies to images. Gamma greatly affects how a digital image looks on a computer screen.

Understanding Gamma in Photography

The term gamma is applicable in photographic terms when we want to view images on computer monitors. The concept is important to grasp (even just on the surface) because the goal is to make a digital image that looks as good as possible on calibrated and uncalibrated monitors alike.

There are three types of gamma involved in digital images:

  • Image Gamma - Used by the camera or RAW image conversion software to convert the image into a compressed file (JPG or TIFF).
  • Display Gamma - Used by computer monitors and video cards to adjust the output of an image. A high display gamma will create images that appear darker and with more contrast.
  • System Gamma - Also called 'viewing gamma,' this is representative of all gamma values used to display the image: essentially, the image and display gammas combined. For example, the same image viewed on a monitor with a different display gamma will not look the same because the resulting 'viewing gamma' is different.

    From Camera to Monitor: How Gamma Works

    Each pixel in a digital image is given a value that determines its level of brightness. The computer monitor uses these values when displaying the digital images. However, CRT and LCD computer monitors must make use of these values in a non-linear way, meaning the values must be adjusted before they are displayed.

    Straight out of the box, a computer monitor usually has a gamma of 2.5. Most modern DSLR cameras shoot with a color space of either sRGB or Adobe RGB and these work on a gamma of 2.2.

    If a computer screen is not calibrated to match this 2.2 gamma then images from a DSLR can look too dark and completely unlike the images shot in the first place!

    Why is Monitor Calibration Important?

    For all of these reasons a set of standards has been set up so the image on your monitor will look like the same image on your neighbor's monitor. The process is called calibration and it is used to obtain a specific gamma reading that is similar to every other calibrated monitor in the world.

    No photographer, whether they be amateur or professional, should work with images without having a calibrated monitor. It is a small investment that will ensure that every photograph you share online or send to a photo lab to be printed looks the way you intend it to. It does absolutely no good to create an image that looks beautiful to you and looks horrible to everyone else!

    You can use a variety of methods for calibrating your monitor, including hardware and software options. 

    The average computer user is not likely to calibrate their monitor.

    This can pose an issue for photographers trying to show off (or sell) their images. However, if your monitor is calibrated, then you have done the best you can to show off your images in the best way possible. The best you can do is to explain calibration to any viewer who sees an image that is 'too dark' or 'too light.'