For now, however, we will confine ourselves to the range of printable values in a straight print, Zones 0 to 9. I have mentioned several times that by doubling the exposure, you can jump from one zone to the next higher one; but how do you double the exposure? Simple! A quick glance at your camera shows that the shutter speeds are (in fractions of a second) 1, ½, ¼,
There is another way to open up or close down a zone: by closing the aperture (i.e., the opening) of the lens. Look at the aperture settings, also known as the f/stops. They are f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, and perhaps f/32, f/45, and f/64. Each of these numbers represents a halving of the aperture from the previous setting. Thus, f/5.6 admits half the light that f/4 admits. F/16 allows only half the light through the lens that f/11 allows. The higher the number, the smaller the aperture and the less light passes through the lens. Again, the camera and the zone system work together in harmony
The photograph contains a full range of tonalities from black to white, yet there appear to be no jarring contrasts. There are small amounts of dodging and burning, but no extensive alterations.
Figure 8-2. Stairway to Cittá Alta, Bergamo, Italy
Table 8-1. Negative density and print tonal scale
Negative Density and Print Tonal Scale
THE NEGATIVE
ZONES
THE PRINT
″
″
″
″
12
13
Double the exposure of Zone
11
12
Paper Base white
Double the exposure of Zone
10
11
Paper Base white
Double the exposure of Zone
9
10
Paper Base white
Double the exposure of Zone
8
9
Paper Base white
Double the exposure of Zone
7
8
Very light gray—no visible textures, but tonally darker than pure white
Double the exposure of Zone
6
7
Light gray—clearly visible light textures
Double the exposure of Zone
5
6
Medium light gray
Double the exposure of Zone
4
5
Medium gray—the 18% gray card
Double the exposure of Zone
3
4
Medium dark gray
Double the exposure of Zone
2
3
Dark gray—clearly visible textures
Double the exposure of Zone
1
2
Very dark gray—no visible textures, but tonally lighter than black
First obvious density
1
Black (no real difference from Zone 0)
No density—film base fog
0
Maximum black
The other confusion comes from the fact that the f/stop number is actually a ratio of the lens opening to the focal length of the lens, so we are really dealing with an inverse amount, or ¼,
The two methods of doubling or halving the exposure, via aperture or shutter speed, point out a very important relationship: one zone is equal to one stop. When you “open up a stop—for example from f/11 to f/8—you are at the same time giving one zone more exposure. In the same way, when you change the shutter speed from, say,
Now that you know what the zones are and how you can jump from one to another with your camera, set that information aside for a while as we look at the workings of the light meter. By combining the knowledge of the zones with an understanding of the light meter, the zone system becomes immediately clear.
Note
As a brief technical aside, it is worth explaining aperture numbers, which seem so arbitrary and senseless at first. The formula for the area of a circle is A=πr2, where A is the area of the circle, r is its radius, and π=3.14159. If you square each of the aperture numbers (i.e., multiply it by itself) and plug them into the formula as r2, they form a simple geometric progression: 4, 8, 16, 32, 64, 128, 256, 512, etc., so that each opening is half or double the previous one.
The Light Meter—How it Works
In order to fully understand the light meter, let’s refer to it by a different name for awhile. The name “light meter” is a bit confusing. We’ll call it a “gray meter” because its only function is to tell the proper exposure for medium gray, or Zone 5. All gray meters do the same thing: they average light within the viewing angle of the meter and give you a reading of the proper exposure for Zone 5. That is the only thing they do!
Note
All gray meters do the same thing: they average light within the viewing angle of the meter and give you a reading of the proper exposure for Zone 5. That is the only thing they do!
The gray meter has no idea what it’s pointed towards. It could be a dark coat in a hallway, a field of snow under bright sun, a person’s face under overcast skies, or anything else you can think of. All it knows is the amount of light that impinges on its lightsensitive cells. Since it has no idea what it’s looking at, it cannot give the proper exposure for the item, so it gives the Zone 5 exposure! For this reason, it should logically be called a gray meter.
Zone 5 may be just the right exposure for many things—perhaps a person’s face under overcast skies (though it seems a bit too dark to me)—but it surely is not the proper exposure for sunlit snow! The difference between you and the gray meter is that you can think! Recognizing that the meter always gives a Zone 5 reading, you can supply your knowledge of the tonal scale to determine the proper exposure.
Let’s take the case of sunlit snow. If the snow has modulations—small hills and valleys—and perhaps even some shadows, you may want it somewhere between Zone 7 (easily seen light gray textures) and Zone 8 (very light gray, almost white—no real textures). Even though snow is white, you probably want to avoid a blank white area lacking in detail. Suppose the gray meter reads f/16 @