Changes in exposure have the sum effect of either lightening or darkening colours, which means that even slight changes in exposure can have profound effects on the overall intensity of those colour and their relationships.
Colours have three distinct qualities:
- Hue — what most people refer to as the colour of an object
- Saturation — the purity of the colour
Exposure in photography controls the last factor in the same way that an artist can alter brightness by adding either white paint to lighten a colour or black or grey paint (or a particular colour’s complement) to darken the colour.
The highly subjective quality of exposure means that you get to experiment with it until you get the brightness levels for the colours that you think are correct. Adding or subtracting light strongly affects the apparent saturation of colours because as you add light the colour brightens and the saturation gets less intense and as you subtract light it appears to be more saturated. By changing brightness you are essentially altering the apparent purity of the colour. The shot of the Massachusetts barn, for instance, the red of the barn seems far more saturated on the underexposed half of the frame.
Because the LCD of a digital camera is a rather poor and inadequate way to judge exposure and colour, it’s often better to cover your own back with a backup exposure system. Far and away the best way to accomplish this is to take all of your photographs using the Raw exposure format (provided your camera offers that option). The Raw format allows gives you at least a four-stop range (two stops over and two under) exposure adjustment after the fact. Unlike other types of exposure correction (the curves or levels controls in Photoshop, for example), changing the exposure during the Raw conversion/import is a non destructive method of editing.
The auto-bracketing feature found in most cameras is a quick way to capture a series of exposure cariations for the same shot.
If your camera lacks the ability to capture images in Raw or if you don’t want to spend the time with the extra editing chores, another simple way to capture a range of different exposures is to use your camera’s auto-exposure bracketing feature. Most cameras (and certainly all DSLR cameras) will let you shoot a series of frames while varying the exposure for each individual frame—typically either in whole stops or incremental stops. The actual number of frames you can fire off in any one sequence depends on the range the camera offers, but even three frames exposed in full-stop brackets will provide a good range of exposure choices.
More importantly, by using HDRI techniques and HDR imaging software, you can actually combine this series of exposures into a single final exposure providing you with a vastly expanded dynamic range—and a more accurate and enhanced colour palette. By shooting a series of three exposures, for instance, you can shoot one frame that exposes for the shadows, one for the middle tones and a third for the highlight areas. In that way you can get a more accurate colour rendition for colours that fall within each of these distinct dynamic areas.
The Photographer’s Master Guide to Color is Jeff Wignall’s thorough course on colour and the role it plays in digital photography, giving you a new understanding of the important role colour plays in the creation of successful photos, and allowing you take outstanding colour photographs with any digital camera.