In Part 1 you looked at some of the basic principles of
the zone system that you should be familiar with if you are going to
understand its ideas fully. In Part 2 you are going to look at a few
more of the basic principles before you go on to apply them in
practice.
The exposure meter always assumes it is pointed at a
"normal" gray surface, even if the surface in reality is
black or white.
An exposure meter cannot tell what it is being aimed at. Is it aimed
at a light or a dark surface? An illuminated dark surface will give
you the same reading as a light surface in a dark room. Whether the
surface that the light meter is measuring is dark or light (in other
words, is reflecting a little or a lot of light), is something that
the meter cannot determine. It is only able to measure how much
light is reflected from the surface; it can give us an exposure
reading for the surface
By exposing the back camera-bag two stops less than the measured
value, it came out properly black. The white surface in the middle
comes out properly white when exposed 2 1/2 stops more than the
measured value.
Always gray
This brings us to something very important; the light meter always
assumes that the measured surface is supposed to be gray. The
exposure reading the meter produces is geared towards rendering the
object's tone as medium gray.
Exercise: Load your camera with black and white film, and go
out and take photographs of objects that have entire surfaces that
are monotone. Vary between white, black and gray surfaces. Colored
surfaces can also be used. Measure the exposure with the camera's
meter or a hand held meter. Expose all the surfaces exactly as the
meter suggests. The camera's automatic exposure can be used with
great advantage. Develop as usual, and print the photographs using
the same exposure time and a normal paper. Every finished picture
will have the same tone.
Deliberately controlling tone
Once you have grasped that using the settings suggested by the
exposure meter means that our photographs will have a medium gray
tone, you can start to think about how to change the overall tone of
the picture. This is done by choosing a setting different from the
one suggested by the meter for the shutter speed and/or the
aperture. If the meter tells us to use f8 and 1/125 seconds, you can,
by choosing f8 and 1/500 seconds, achieve a tone that is two stops
darker. 1/500 seconds is two exposure stops shorter than 1/125
seconds, the film will be two stops less exposed, and therefore the
picture two stops darker. You can also make the picture lighter by
choosing a longer shutter speed or a wider aperture.
The chapel of the Atlantic island Madeira, didn't have any
windows. The contrast was extremely high. The left picture was
exposed using an average measuring method. The result is a negative
with no details at all behind the door.
In the right picture exposure was calculated after measuring the
darkest parts with a spot-meter, ensuring negative details in the
shadows. The over-all contrast was reduced with less development of
the film. Once you know how to control the picture's tone, you can
photograph any object of any tone and get it right at the first
attempt. You simply choose a setting for the exposure that will give
us the correct tone.
Exercise: Load the camera with black and white film, and go
out and take more pictures of surfaces, only this time practice
altering the exposure. For example, when you shoot a dark surface
the exposure can be reduced two stops. Light areas demand an
increase in exposure, so try increasing two or three stops. Grey
areas should be exposed according to the meter's suggestions.
Develop as normal, and print all negatives on a normal paper with
the same exposure for all the negatives. Choose an exposure where
the gray surfaces come out gray, and the other surfaces will then
automatically come out right.
Making a comprehensive exposure scale
The next problem is that you do not know how much lighter or darker
the image will be when you change the exposure by a certain number of
stops. You are therefore going to create a test series of exposures
to establish the picture tone.
Exercise: Place a gray card outdoors so that it is evenly
lit. Point the camera, loaded with black and white film, at the gray
card without shadowing it. Focus on infinity. Measure the gray
card's exposure with the camera's meter or a hand held meter. Start
by decreasing the exposure by four stops: thus, if the meter reads
f8 and 1/125 seconds, set the camera to f11 and 1/1000 seconds. Take
the first picture. Increase the exposure one stop (to f8 and 1/1000
seconds) and take the second picture. Continue until you have taken
nine pictures, which will mean that you have a picture for every
setting from minus four stops to plus four stops. Develop the film
as usual, and print all nine negatives using the same exposure and a
normal paper. If they have been correctly printed, you will have a
scale ranging from totally black to totally white with seven stops
of gray in between.
Using this gray scale to help, it becomes much easier to choose
an exposure regardless of what you are photographing. It is makes no
difference if you are photographing a black, white or gray surface;
with an exposure meter and the help of your gray scale you can give
the photographed surface any gray tone you wish. All you have to do
is adjust the exposure in the appropriate direction. Increased
exposure (wider apertures or longer shutter speeds) provides tones
that are lighter than medium gray. Decreased exposure (smaller
apertures or faster shutter speeds) provides tones that are darker
than medium gray.
Underexposure
By decreasing the exposure by 3.5 stops, you reach the limits of
underexposure. By decreasing the exposure by more than 3.5 stops
from the measured value, the negative will be blank and the picture
will print as totally black. This limit has to be watched out for.
It is best to make sure than none of the object's detail ends up
beneath this limit.
The threshold for under-exposure is situated 3 1/2 stops left of
(under) the measuring point for the exposure meter (the arrow).
Knowing this will make it easier to expose black and white film
correctly. Confronted with an object to photograph, you start by
identifying the darkest and measuring the exposure there, and you
then adjust the exposure to ensure that this area ends up slightly
above the underexposure limit. The exposure the meter will suggest
will give this a medium gray tone, but you do not want the darkest
part of the object medium gray; you want it to be black. Thus you have
to decrease the exposure. The gray scale will help us decide by how
much you need to decrease the exposure. Two stops may be sufficient.
If the exposure meter gives a reading of f4 and 1/30 seconds, we
should set the camera to f5.6 and 1/60 seconds. This will make sure
that the darkest part of the object will appear on the negative. Set
your exposure according to the shadows.
Ansel Adam's exposure zones
Ansel Adams chose Roman numerals for the exposure stops, which he
called zones (exposure zones). He probably did this to give the
different exposures separate names rather than talk about minus one
stop or plus two stops. In Adam's terminology, the 'normal' exposure
is called Zone V. A Zone V exposure is the exposure you get if you
use the reading the meter provides, without changing it. If you
decrease exposure one stop you get a Zone IV exposure. If exposure
is increased three stops, you get a Zone VIII exposure. In other
words, the numbering system starts from the normal Zone V exposure
and then adds or deducts one for each of the stops by which the
exposure is increased or decreased.
Zone 0, which is so underexposed that the negative will come out
blank, is five stops beneath the normal exposure. Zone I is also
under the underexposure limit: it may give you some detail in the
negative, but it is still essentially useless to print from. To be
able to distinguish detail from the wholly black in the finished
photograph, it has to be exposed at least in Zone I 1/2 and
preferably in Zone II. Detail exposed in Zone III will be very
distinct in the finished print.
Brighter details need to be exposed using the higher zones. Zone IX
will be totally white when printed. Zone VIII will be almost white.
Details that are supposed to appear white should be exposed
somewhere within Zones VIII to VIII 1/2.
The zone scale
The gray scale described earlier can also be called a zone scale,
which is arrived at by numbering the grays with Roman numerals from
I to IX. The scale is used to help us see what the different zones
(and their exposures) will look like in the finished photographs.
The advantage of the zone system
Getting the exposure right is probably the most important part of
the zone system. When you have learnt how to determine the correct
exposure using to the zone system, you no longer risk ending up with
underexposed negatives. You can photograph the most difficult
objects without losing fine detail, and a correctly exposed negative
is the most important prerequisite for photographs that are rich in
tone. It is not a disaster if the contrast is not spot on - that can
always be adjusted in the printing - but an underexposed negative
will never give you a good picture. If you choose too fast a shutter
speed or too small an aperture, inevitably important detail will be
lost that cannot be retrieved in the dark room.
<- The Zone System - Part One (previous)
The Zone System - Part Three -> (next)
