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The zone system was first developed in the early 1940’s by Ansel Adams, a reknown landscape photographer. The zone system is a method for determining optimal exposure by visualizing the final result of the photograph and then placing your exposure to achieve it.

The zone system starts at pure black and then increases exposure by 1 stop per zone till it reaches pure white. From pure black to pure white there are 11 zones, each 1 stop apart. The image below illustrates the tonal values of each of the 11 zones.

Zone 5 importantly is middle-gray. A light meter gives exposure settings to produce middle gray, so whether you point it at a white wall or a dark tar road, it will change its reading so that if you shot that object in black and white, it would come out as middle gray. A light meter gives the correct reading to make any object being measured come out as middle gray. By learning the different tonal values of each of the zones and the types of objects they accurately resemble in real-life, one can start to determine optimal exposure. For example, if you were to point your spot light meter (or zoom in with your camera’s spot meter) at a white piece of paper, and the exposure setting given by your meter was read at f8 1/60th sec, you’d know that this would be the correct exposure to use to make the paper middle gray or zone 5. But because you know that plain white paper should be about zone 7, you can now adjust your exposure to be two stops brighter and shoot at f4 1/60th sec and get the correct result. By using the zone system in this way, you can now ensure that you get accurate results from your exposure choices or alternatively use it to produce more creative work that you envision.

Zone system for a single object is easy, since you just have to match the zone to the object’s natural tone. When dealing with more complex scenes, one has to sometimes ‘shoot-to-process’. This is when capturing the scene accurately will not be in your best interest because parts of the scene may be lost to over-exposure or under-exposure. In the zone system, you can be confident of capturing detail from zone 3 to zone 8 – these are the zones at which texture is still fully captured. On either side of this range you begin to only notice gradations in tone, but it will be too dark or too light to distinguish detail. This means you have a 6 stop range to work with from lowest value that you want to capture detail in to highest value with detail. You may now have to adjust your exposure so that as much of what you want to capture can be included in that range.

For example: You are shooting a landscape with a rocky canyon in the foreground. You recognise that some of the darker rock should be zone 4. Your lightmeter reads this as 1/60th sec f5.6. – (the reading for middle gray, zone 5) Therefore you’ll want to expose at f8 to make the rock zone 4. When you meter the sky (excluding the sun itself) it comes out as zone 8 ½ to zone 9. You realise that this will produce a pretty much white sky and losing some detail, which is not what the seen looks like as you visualise it. Because the sky is important to your shot you adjust your exposure, knowing that you can safely expose the rock at zone 3 and still capture detail. This will bring the sky into the more acceptable range of zone 7 ½ to zone 8. You know that since you’ve got all the detail in your exposure you can now leave it up to digital processing to place the values where you want them to be. In photoshop, you can now boost the shadow tone to restore the rock to zone 4 and you can also adjust the highlights down to produce an even more dramatic sky. Using the zone system is both a tool for effective picture-taking and an intelligent way to plan how you will achive your results through manipulation at every stage of the process, from the capture your camera takes, to the processing and post-production you do on your computer. Zone system also has application in studio photography where you can exert more control over your lighting choices to produce your envisioned exposures.

Zone System Applied to Exposure Setting

	Exposure Settings: 1/60th sec; f8; ISO 100 At this setting the canyon is perfectly exposed with rock in the shadows falling into zone 4. The spot meter reading of the rock was f5.6. The sky area (not directly on the sun) though falls into the zone 8 1/2 to 9/12 zones, causing detail to be lost and resulting in a very bland image.
	Exposure Settings: 1/60th sec; f11; ISO 100 This shot was taken four minutes later and with the exposure adjusted down a stop, the sky area now shows more detail with values falling into zone 7 1/2 - 8 1/2. While the rock is now not ideally exposed it still falls into the zone 3, which means that the camera will still capture the detail and can be worked on later.
	This is a modified version of the above picture. Using photoshop, the lowlights can be increased by 1 stop back to where they should be and the highlights can be further underexposed to deepen the sky and make it more dramatic. It is important to note that this kind of post-production is only possible because the image detail was captured in a usable range.

Using the zone system is both a tool for effective picture-taking and an intelligent way to plan how you will achive your results through manipulation at every stage of the process, from the capture your camera takes, to the processing and post-production you do on your computer. Zone system also has application in studio photography where you can exert more control over your lighting choices to produce your envisioned exposures.