The reality of photography is that scenes are rarely lit by a single, uniform light source, day-lit landscapes being the exception. Rather, many spaces reflect light from multiple different sources, each with its own colour temperature and characteristics.
Generally, there are three approaches to dealing with mixed lighting, the easiest being to simply set your camera to Auto white balance and let it determine an average colour temperature for the scene. Depending on how diverse the various light sources are, this can work quite well: greys and whites may be skewed a bit, but no single colour will be completely off-target. Or you can go the opposite route and set your white balance for only one particular light source, leaving all other colours to shift accordingly. This can be a good approach if one light source is dominant, and the inaccurate colours aren’t too distracting.
The final and best option for colour correcting mixed lighting involves adjusting each light source separately, and can be done only in post-production. There are a few different approaches here, but the most effective is to use the Replace Color tool in Photoshop: Image > Adjustment > Replace Color… . This allows you to isolate one particular colour and shift its hue, saturation, and lightness independent of all other colours, bringing it into harmony with the rest of the scene.
City lights can be considered the ultimate style of mixed lighting. Vapour lamps are now a common choice to light municipal areas, and require a deft diagnosis of which variety is being used. In combination with this, a shop-lined street will often shine forth a row of tungsten-lit frontages, while neon is used overwhelmingly in certain other districts.
The light within shops, malls, and other commercial buildings is meticulously designed to encourage consumers to linger, persuade them to move on more quickly, or plot a particular course through a retail space. For this reason, the current trend is to use a mixture of incandescent, vapour discharge, and fluorescent lighting to achieve the desired effects, and this must be accounted for by the photographer. Fortunately, the effort put into the lighting design pays off with a well composed and delicately balanced scene, which is often simple to photograph. Indeed, high-end shops and galleries go to great lengths to ensure their ambience is worthy of their expensive goods and services, offering up lush photographic subjects.
Learn to “read” light in this complete course on the building blocks of photography. Michael Freeman teaches not only how to see the subtle nuances of light and shade, but also how your camera views and records them, to make sure you approach each scene with the optimal settings and appropriate technical know-how.