Light meters are very useful tools in photography. They are small devices that can measure the levels of light in an area or near a subject and display aperture and shutter settings to give a ‘good’ exposure, as long as the photographer has entered the correct ISO settings. However, light meters do not have smart technology. The readings they give out wouldn’t take into account the full tonal range of the proposed image, simply an average of the tonal range or ‘Middle Grey’. A good example of this is when taking a black and white image of a snow scene, the snow wouldn’t come out brilliant white as it naturally is, but would come out as a dull shade of grey.
And so, the photographer Ansel Adams invented a very useful zone system referring to the different tones in black and white images, which allows the photographer to pre-visualise the image, and become a Pro Active Photographer (The camera says what the photographer wants to say, rather than just recording the image). The zonal system is shown below, with each number representing a different tonal area:
- 0 – Pitch Black – No Detail
- 5 – Mid Grey
- 10 – Bright White – No Detail
As I mentioned before, the settings given out by light meters gives an exposure at the Mid Grey level or level 5, and so Ansel Adams then used these settings to decide whether to under expose or over expose the image. He did this by reading the levels and then adjusting the camera settings accordingly. For example when taking an image where the photographer wanted to create a silhouette, and the light meter gave out an aperture of F5.6 and a shutter speed of 80, then the photographer could adjust the settings to expose the light rather than the subject, which would remove the detail and create a silhouette.
By keeping this method in mind the photographer can create the exact image that they want and make the scene look how they want it to look. This method is extremely useful for digital and analogue photography, with adjustments being done in the developing stage of the film to either over develop or under develop the film.