However, before I extol its virtues you must realize that there are as many means in determining exposure and there are photographers doing it. To some photographers the Zone System comes naturally. To some it takes some time wrapping one's head around it. Some think it way to cerebral and that it takes away from the experience of photographing. So, the Zone System might not be for you. But I use it in all of my serious work.
In 1940, Ansel Adams and Fred Archer were teaching a photography class at the Los Angeles University School for the Arts. They wanted to create a system whereby students could determine their own exposure consistently. They did not want to lead the students by the nose but, rather, show them a way to do it themselves. After reading articles in the magazine U. S. Camera in that year they devised what would come to be called the Zone System. The premise is that film has a certain exposure latitude, a range of light values that will be rendered on film and in the resulting print. Using this system allows the photographer to determine what range of light is present in the subject and to 'place' those values into the negative and print.
Zone 0: Black. No useful detail.
Zone I: Near black. No useful detail and only minor tonal separation from Zone 0.
Zone II: Noticeably lighter than Zone I and containing the beginning of useful detail.
Zone III: This is the lowest zone where there will definitely be useful detail in the subject.
Zone IV: Lighter still.
Zone V: Middle Gray. 18% Gray. This is the value that most light meters are programmed to duplicate.
Zone VI: Lighter still.
Zone VII: This is the brightest zone where you can expect consistent useful detail.
Zone VIII: Lighter still. There is tonal separation in this zone from Zones VII and IX, the upper end of useful detail.
Zone IX: Near white. No useful detail and only minor tonal separation from Zone X.
Zone X: White. No useful detail.
When you are placing your subject into the zones you will find good detail in the values between Zones II and VIII. This is the Textural Range of the Zone System. There is good tonal separation in the values between Zones I and IX. This is the Dynamic Range of the Zone System.
Now, how to use it.
Log and Ferns - Bombay Hook NWR - Woodland Beach, Delaware - 2014
Take the photograph above. You can see the shades of gray throughout the photograph. There are some highlights, not white but very bright. There are also some deep shadows, perhaps not black but very close. The bark on the log just beneath its sunlit top is right at Zone V, middle gray. The sunlit bark on its top would be Zone VIII, very bright and still detail in the bark. The shadows beneath the center of the log and next to the trunk in the upper left corner are about Zone I, dark with no detail. You can go through the picture and assign exposure zones to the values you see to get the basic idea of how these zones are represented.
Note: Two terms for consideration. Placing: indicates an intentional action: by choosing an exposure setting a tone is placed on a specific exposure zone. Falling: by placing one tone on a specific zone, all other tones fall onto respective zones above and below the originally specified zone. Also, if you are adjusting your exposure on purpose, I would refer to this as increasing and/or decreasing exposure as opposed to overexposing and underexposing which generally refer to errors in exposure rather than a conscious departure of creativity.
If you came across this scene and, instead, wanted the bark on the top of the log to be darker, say just above middle gray, Zone VI, you could have adjusted your exposure settings and placed that value on Zone VI instead of Zone VIII. However, when you do this the rest of the values 'fall' onto corresponding zones. The bark on the bottom of the log would not be Zone III but Zone I and you would lose all detail there. If you were to decide to place the bark on the side of the log on Zone VII instead of Zone V the other values would fall onto higher zones. The bark on the bottom would have great detail on about Zone V but the bark on the top would be completely washed out in Zone IX or X.
Using the Zone System you can completely control the exposure of your film and where in the range of light values specific portions of your subject will fall based on your placement of a single portion of the subject. And it is essential to learn how to use a good light meter to achieve this control. The better your light meter, the more consistent your results will be.
Before we get into this in great depth a little explanation of how a light meter works is in order. LIGHT METERS ARE DUMB! Your light meter does not know that the snow you are metering is white anymore than it is aware that coal is black. If you meter a white wall and expose according to that reading then the wall will appear to be middle gray, 18% gray. If you meter a black road and expose based on that reading then the road will appear to be middle gray, 18% gray.
This is because all light meters are meant to only suggest to the photographer which exposure value will give an average and, most times, acceptable exposure. I said average, read: 18% gray. You might want that snow to be bright if not white. So you would need to increase your exposure anywhere form three to five stops to raise it from Zone V to between Zones VIII-X. You may just be on the edge and decide that the black asphalt should look, well, black. So you would need to decrease your exposure from three to five stops to lower it from Zone V to between Zones II-0.
See, you can control how your subject is captured on the film by metering your subject well. Meter the brightest important spot in the subject and note it down. Meter the darkest as well. The meter other areas and see what their values are in relation to the shadows and highlights. Settle on an exposure value and make your photograph.
Most handheld light meters have a wide angle of measurement, generally around 30 degrees. There are 5 degree and one degree spot meters that can allow you to meter a very local portion of the subject without needing to leave the camera's location, providing you with more accurate results as you will be metering the light reflecting to the camera as you will be standing by the camera. I use a one degree Soligor spot meter for my large format photography. It allows me to meter under the log, the top of the log, a single leaf on the fern, you get the idea.
Regardless of what gear you use, know its limitations and strengths. Use it to your advantage and you can be the master of your own photography.
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