Looking on the back of the camera to see if you got a shot properly exposed can be misleading. The LCD may not be calibrated showing a too dark or a too light image. Or the sun hitting the LCD can be laying tricks on you.
Yet there is a tool, that is often ignored that can give you a very quick and good indication if you exposed correctly – The Histogram.
In a nut shell, the histogram is a graph that show how many pixels of each brightness level are present in a frame. John Greengo of CreativeLive give a full back to basics course on photography, in this installation he discusses the Histogram in very easy to understand manner.
Generally, John mentions that you would want a histogram that looks like a mountain with a strong peak in the middle and a slope that goes out to either end. While specific captures may be unique, (such a capturing snow, or night shots), a strong peak on the right may indicate an over exposed image, while a strong peak on the left may indicate an under exposed image.
Here a sample image from John’s course that illustrates the point. Remember, the shape of the “mountain” in the middle may vary, but you are probably good if you don’t see any peak that touches the left or right edges.
How To Display The histogram on Your Camera:
Canon DSLRs – While in review mode, hit the info button. A histogram will appear next to the image. Hit the info button again to show the RGB histograms. You can do the same while in Live view – hit the info button to show a histogram while in live view.
Nikon DSLRs – This kinda depends on your model. While in review mode hit the 4-way selector up or down until you get to the histogram overlay mode. If up/down moves between photos, press the left/right arrows. Sadly, Nikon changes the way up/down and right/left work around 4 years ago.
Sony DSLRs – Press DISP (Display Contents) repeatedly in shooting mode to display histogram.
Pentax DSLRs – Press info and then the right and left arrows to get to the histogram view. then use the up down arrows to toggle standard/RGB histograms.