How do I use the Zone System?
Click on this link to see a pdf file on using a Pentax Digital Meter with the Zone System. Note this meter does not come with the Zone system overlay. You can be purchased it separately for $3 from Calumet or make your own.
The late, great photographer, Ansel Adams, devised the Zone system as a way to think about all the shades between pure black and pure white. He divided that range into ten Zones, each one one stop different from the preceding and the the following. Middle gray he set as Zone V.
Every reflective meter on every still camera and every spot or reflective meter reads Zone V. That means, if you take a reading with your reflective meter, and expose your film at the reading, what you pointed your meter at will expose as middle gray, Zone V. How can that work? It turns out that the average light on a scene is Zone V except in extreme conditions. So if you are looking through your Nikon camera and the meter tells you to expose at say 5.6 with a 1/50th shutter, the meter has averaged out the scene to tell you this setting and unless the scene is severely backlit or the central character is a small blip in a scene of black or white, your exposure will be pretty good.
When it comes to using 1° spotmeters, these meters cannot average out a large scene. But what they can do is very accurately tell you where each element in the scene falls. The wide-spread way to think with a meter such as the Minolta Spot is, "Oh, I'm pointing at a caucasian face. The meter tells me to expose at T-8. If I do that, the face will be too dark since it will be exposed as if it were middle gray. Therefore I should open up 1 stop to compensate and expose at T5.6."
I find such thinking confusing. Enter the Zone system. Unfortunately at this time the only meter that easily reads out Zones is the Pentax Spotmeter, either the old analog version, or the newer digital one which is more sturdy, smaller, and easier to use.
There are two different ways to proceed with the Pentax. Either use it to first set the base exposure for the scene, and then check where elements within the scene fall, or use an incident meter to set the base exposure and then, again, check where elements within the scene fall.
To use the Pentax digital spot to determine base scene exposure you can:
The next step is to see where do other elements in the scene fall, and do I want to change the lighting on of these. Leaving the dials exactly where we placed them for our base exposure, we can now point the meter at different parts of the scene.
Unfortunately, we have to know something more: how does the negative we are shooting respond to the full spectrum from black to white. Some stocks, such as Kodak 52/7229, have very flat curves at the toe and shoulder, and so can read into the shadow and highlights quite well. Other stocks, such as Kodak 52/7245, block up quickly. So it's not exactly correct to say each Zone is 1 stop different from it's neighbor. It may be somewhat less, or somewhat more. But the Zone system is a great starting point to thinking about and previsualizing each scene we shoot.
Over the years I have found I rely on my spotmeter and the Zone system more and more and more. Of course, other cinematographers will have different methods. For the beginner, I cannot emphasize enough that learning to use this system is an excellent way to wrap your mind around exposure.
Here is a table of Zones. I have not attempted to reproduce the correct grays for each.