What is the Zone System?
Developed by the legendary Ansel Adams and Fred Archer, the zone system remains as the definitive way to properly meter a scene. It was developed back in the 1930s and is still being used today by photographers. If you are thinking that it is inconsequential in the context of modern digital photography, think again. It is very much applicable.
Once you understand the core concepts of the zone system, you would never look at a backlighting scene or for that matter any difficult lighting condition with the same amount of trepidation. You would walk into any lighting situation and be able to meter it correctly.
Metering in photography
One of the most difficult things in photography is to meter a scene manually. By the way, your camera’s built-in metering system is not exactly full-proof. It averages scenes based on luminosity and tries to make them 18% gray or middle gray. That becomes a problem at certain times.
For example, a pure white background and a pure black background will both appear middle-grey when you shoot in the matrix (evaluative in Canon cameras) metering mode.
This is because the camera’s metering system has been designed to make everything middle gray.
The camera sees something very bright, like a patch of snow or white clouds, and deduces it is too bright and under-exposed. On the other hand, when it sees something very dark like a big elephant, it decides to over-expose it.
The zone system developed by Ansel Adams and Fred Archer
The zone system divides any scene into 10 different zones based on their luminosity. It is a system that starts from pure black, which is ‘0’ and goes all the way to pure white which is ‘X’ (ten in Roman).
Right at the middle of that scale at zone ‘V’ is middle-grey or average luminosity. Each zone is a stop different from the zone next, in terms of luminosity, by one stop. That means if you move from ‘V’ to IV’ there is one stop loss of luminosity and if you move from ‘V’ to ‘VI’ you gain one stop.
Applicability of the zone system in digital photography
In digital photography, however, that entire 0 to X scale of luminosity is not used, rather, not applicable. A scaled down version which starts from zone ‘V’ and goes two stops either way. i.e.; ‘III’ and ‘VII” is used. ‘III’ is where the darker bits of the image would be and ‘VII’ is where the brighter bits would be.
Anything beyond zone ‘III’ and it would be pure black (no discernable details) and anything beyond zone ‘VII’ would be pure white, completely blown out. When metering for a scene you should look to
When metering for a scene you should look to place the brighter areas (but not the blown-out bits) right about in zone ‘VII’. This should ensure that the middle gray is in zone ‘V’ and the darker bits to be in the zone ‘III’.
Using the modified zone system to meter a scene
The best way to use the adapted version of the zone system is to use it in conjugation with exposure compensation. Also, this adaptation will work better if your select spot metering instead of partial or evaluative metering modes.
Start by placing a bright area of the image as the point of metering. This considers that you have already switched to manual mode before doing this, adjust the exposure for this point. Now, use this as a reference point and dial exposure compensation so that it is set to positive 2 stops. This is your zone ‘VII’ (remember, zone VII is two stops brighter than zone V).
Following this rule, the darker bits in the image should fall in the zone ‘III’. But it is just a guideline. There may be scenes where the darker bits are beyond zone ‘III’, say in zone ‘II’. But we as photographers are only considered till zone ‘III’. In such a situation you could either choose to keep the brightest aspects in zone ‘VII’ or the darkest bits in the zone ‘III’, as fitting both in the right zones is impossible.
Shooting in RAW gives you that extra leg room to salvage details and correct the exposure in post-processing in such really difficult lighting conditions.
Related Post: Shooting in High Dynamic Range