The Zone System was created by the famed photographer Ansel Adams.  Ansel Adams did a lot of innovation in his day to advance the theory and technology of photography, and it can be seen through his work.  He actually wrote books about developing not just film, but your own film emulations and how to find the ISO of your own films.  A lot of that came because he started off hauling around a darkroom because thats what the technology was when he began, and although a lot of what he wrote about seems a little out-dated, much of it is still important to know today; the zone system is one.

Essentially, the Zone System is a way of determining exposure not only for your initial in-camera exposure, but then to a print.  Previously I have talked about exposure and this was one of the first things that I learned about so I am sharing it summed up for you here.

Here is a graphic for Ansel Adams Zone System. These are 4 parts in this graphic (top to bottom):
1.  The 11 Zones separated into sections
2. A simple gradient representation
3. The Zone Numbers
4. Grayscale Values

So, hows it work?

First, this is basically set up for Black and White photographs, although the general idea is for proper light exposure.  Even if you are shooting in color these principles will still help you to understand exposure and make your photographs better. With that understood lets take a look at how it works.

With the zone system there is a zone associated with all levels of brightness in an image.  The darkest parts of the image are Zone 0, while the brightest parts are X.  A more in-depth description is below.

When taking a photograph you are trying to capture all the detail around the II -VIII range.  The extremes of the zones represent what would be completely black or completely white. You might notice that Zone V is slightly bold in the graphic above, and this is because the general idea is that your exposure captures middle grey is historically what meters look for, so by exposing your photograph properly all the details will be represented across the spectrum.

The Zone System allowed Ansel Adams to make an exposure, and then match the negative with the prints he produced.  It is still applicable today because in every scene, by exposing for the middle ground will give you the shadows and the highlights appropriate for the scene, whether for Black and White or Color images.