make use of the graph
Should I be using my camera’s histograms more? Ronnie Yeoman
Andrew says Anything that helps you get the exposure right in-camera is worth using – and that is exactly what the Brightness Histogram does. We’ve briefly touched on histograms in a past Photo Advisor, but if you are not sure what a histogram actually is, it’s simply a graphical representation of the tonal range in the image. There are 256 different RGB tones starting at black and finishing at white.
The histogram can be used to make sure that you aren’t either over-exposing (making it too bright) your photo or underexposing (making it too dark).
As a general rule, I try to shoot so that the tones in an image are pushed to the right as far as possible without over-exposing. This means I’m spreading the tonal range, and it gives me a good basis to work on in post-production.
When I look at the image in the LCD, I can get a good idea of whether the exposure is OK, but only the Histogram will really show me whether I can afford to dial in some exposure compensation for a better exposure. At this point I should add that there is no such thing as a perfect histogram – it all depends on the tonal range in the scene you are using. It is also possible that some overexposure or under-exposure is a natural part of your image: if you are shooting a silhouette, for example, then obviously part of that image will be black, and therefore technically underexposed. Conversely, if you are shooting a picture with the sun in it, then it’s likely the brightest area will be beyond what a digital camera is capable of capturing, and therefore over-exposed.
Essentially, the Brightness Histogram is a useful guide to help you make the right exposure decisions, but it’s not something I’d advocate you checking on every single photo during a frantic shoot. If you did that, it would be too easy to spend all your time ‘chimping’ on the back of the LCD and not enough time shooting. Just use it when you first start shooting or if you suddenly notice the light has changed dramatically, and I think this could well alter the exposure you need.
If you don’t know how to access the Histogram, check your camera’s manual. In many cases, it is activated by pressing the Info button when there is an image already being previewed. You can also view it while shooting in Live View.