10 Introduction to Filming in Low Light
There may be occasions when you need or want to film in low light conditions. It could be that there is no additional lighting available, or restrictions are placed on additional lighting or that by adding additional lighting you will interfere with the atmosphere at the event. Or you may simply be trying to create a scene which is supposed to look dark.
Filming in these situations will test the capabilities of your camera and your ability to capture images of sufficient quality. Each camera will require different levels of light to produce images without artificial ‘gain’ (electronic image enhancing) being added to the pictures either at the filming stage or in post production. Whilst using gain will increase the light sensitivity of your camera it will also introduce ‘noise’ or ‘grain’ to the picture. This will also be the result if you brighten the picture in post production.
10.1 Camera Performance
Cameras are rated by their ‘Lux’ rate. Lux is the SI unit (the International System of Units, abbreviated to SI from the French, Système International d’unités) of luminance. It is used as a measure of light intensity according to the human perception of brightness. The lower the Lux rate, the less light is required in order to produce a sufficiently bright picture without using artificial gain. To give you an idea of Lux levels: moonlight is generally measured at around 1 Lux; the average living room with tungsten lighting is around 50 Lux; and sunlight on an average day is measured at around 32,000 Lux.
10.2 Focus & Operation
Operating a camera under low light conditions can be difficult. Focusing will be particularly challenging, and Auto Focus will not be as accurate as in normal lighting conditions (or may not work at all) so should be avoided. In addition, your viewfinder or monitor will be more difficult to use. The temptation will be to increase the viewfinder brightness to adjust focus but this will not give you a true representation of the images being recorded. Adding gain will help to increase the camera’s sensitivity, but in extreme cases the resultant gain might warrant your pictures unusable.
10.3 Best Working Practices
Whilst filming in low light will result in compromises, the best method to adopt is to use shots with a short focal length. With video zoom lenses, the wider the lens is set (zoomed out), the shorter the focal length will be. Conversely, the more you zoom into the lens range, the longer the focal length will be. Adopting a shorter focal length will allow more light to fall on the camera’s image sensors therefore making the most of the available light.
By fixing the focus at a set distance (say, 3 metres), and ensuring that you are keeping the subject this distance from the camera lens at all times (and still maintaining a short focal length), will result in the best possible images in low light situations.