The obvious difference between color prints and black and white prints is that the black and white prints have no colors. Color as a medium of information is very important in color prints, so to compensate for this in black and white photography You have to be much more aware of the problems of working with a gray scale. The gray scale is the black and white print's 'color', the most important provider of information, and in order to master the gray scale You must control the contrast.
Fortunately it is much easier to control the contrast in black and white film than it is in color. All negative color films are developed to the same contrast, and generally there is only one contrast grade of color paper. Slides are also developed to the same contrast. The most important way of limiting contrast in color pictures is to pre-expose (or post-expose) the film slightly, which will decrease contrast in the darkest areas.
Even though You hardly ever do anything about the contrast in color prints, most of the time You still accept them as good pictures.

Black and white contrast
When you work with black and white there are many ways of controlling the contrast. The most common is to use a different grade of paper or to filter a variable contrast (VC) paper.
Most people working with black and white follow one set of instructions, and hardly ever change the development time. Development time is in fact an excellent tool for controlling the contrast in black and white film. Shorter development times give you a low contrast negative and longer times give you a high contrast negative.
As with color film, you can also decrease the contrast by slightly pre-exposing the film before use. This can also be done to the paper while printing. Pre-exposing the paper decreases the contrast.
These different methods of controlling the contrast affect the final photograph in various ways. An alteration in the development time changes the contrast evenly. A strongly reduced development time may make even the darkest shadows disappear, something that has to be compensated for by increasing the exposure.
Different paper grades also affect the whole tonal scale more or less evenly. If you are forced to use a really high contrast paper (Grade 4 or more) the detail in the darkest shadows and brightest highlights may be lost. VC papers will not give you as even a change in contrast as graded papers, although it should be noted that some VC papers will have a more even effect than others.
Pre-exposing the film reduces the contrast only in the darkest shadows, while pre-exposing the paper reduces the contrast in the brightest highlights.

Aim to use a normal paper
In his final version of 'The Negative', Adams recommended using the film development time to control contrast, but he also warned against becoming obsessive about it. Despite all claims to the contrary by many zone system experts, the idea is to be able to print every negative on a normal paper. According to Adams, you should try to find a development time that works with Grade 2 paper, but that said, having to use a Grade 1 or Grade 3 paper is not a disaster. The reason for aiming to use Grade 2 paper is that you can then use Grade 1 or Grade 3 if you have to. If you set out to use a Grade 3 paper you may end up having to use Grade 4, loosing shadow and highlight contrast in the process.

Which contrast?
There are many reasons why you should vary the contrast when making black and white prints. The contrast inherent in the object varies. Soft light that casts no shadows requires a negative or paper with a high contrast. Harsh light creates pictures with too much contrast if not compensated for by a low contrast negative or paper.
Some objects do best with less contrast, others need more if they are to come out well in the final print. Tastes differ. Some people prefer soft pictures, others prefer them with a higher contrast.
Before You go further into the zone system's method of contrast control, and the terms used to describe this, You will take a closer look at the zone scale and the different zones.

A schematic picture of a zone scale from 0 to X. The border between black and almost black is marked between zone I and II (zone I 1/2). The border between white and almost white is between zone VIII and IX (zone VIII 1/2).

Blackpoint and whitepoint
There are two very important points indicated on the zone scale shown in the figure the blackpoint and the whitepoint. The blackpoint comes between Zones I and II, and the whitepoint between Zones VIII and IX.
The blackpoint is the point where totally black becomes nearly black. Details that are exposed so they fall into a zone beneath Zone I 1/2 will be more or less absent from the negative, and the print will be wholly black and devoid of all detail. Details exposed in Zone I 1/2 and up will appear on the negative.
At the other end of the scale, details exposed beyond the whitepoint at Zone VIII 1/2 will come out totally white in the print if You do not do something lower the contrast. Unlike those at or beyond the blackpoint, these details are present on the negative, and by choosing a low contrast paper or by using post-exposure You can make these details appear in the print.

The different zones
Zones 0 and I will always appear totally black when printed. Occasionally you may be able to obtain some tone in Zone I, principally if you have used a short-toed film and paper with a short shoulder.

Zone II will be distinguishable from totally black on the negative and the paper. Very dark details in shadow should be exposed in this zone.

Zone III shows distinct texture.

Zone IV will be slightly darker than medium gray. Skin tones in shadow and dark foliage are suited to this zone.

Zone V is the one to which exposure meters are adjusted. The intent is to make Zone V appear medium gray in the finished picture. Since the choice of film and paper affects the tone, do not try to follow the gray card too closely when printing Zone V.

Zone VI is light gray. Well-lit pale skin tones come out best in this zone, as do snow and white sand in shadow.

Zone VII approaches white, but can reproduce detail with distinct texture.

Zone VIII is almost completely white.

Zones IX and X are usually completely white. Using a softer paper, shorter development time or post-exposure when printing, You may be able to make even these zones appear in the final print.

Zone placement
When using the zone system to decide upon the exposure and development, you normally use a type of exposure meter called a spot meter. This measures the light for only a very limited area of the object. Many modern cameras have a built in spot meter that can be used for this purpose. You take a selective measurement of a small part of the object.
However, before you measure the exposure, you have to consider how you want the different details of the object to appear in the finished picture. The best way is to look for details that will be reproduced as relatively dark in the picture.
Say You start by finding a detail You will want reproduced in Zone III. You want it to appear as very dark in the picture, but You also want to maintain its texture. Point the spot meter at this area and take a measurement. Since the meter will always want the exposure to be in Zone V (making everything medium gray), the exposure has to be adjusted to Zone III. Since Zone III is two stops darker than Zone V, You will have to reduce the exposure by using a smaller aperture or a faster shutter speed. If the meter suggests f8 and 1/30 seconds (8/30), You can choose to use 8/125 to get an exposure in Zone III. You will set the camera to 8/125 when You photograph the object. To use zone system terminology, You say that You placed the detail in Zone III.
When the placement - and thus the decision on the whole exposure - has been made, the next job is to check where the remainder of the object details fall. All this really means is that You check the contrast. Point the spot meter at the brightest area on the object and read off the value. Calculate how many stops brighter than Zone III it is. Take the difference and add three (since the placement was made in Zone III) and you will know which zone the brighter detail falls into. For example, if the reading for the bright area is 8/1000, it is five stops brighter than the dark area You measured first (the difference between 8/30 and 8/1000). 5 + 3 = 8, thus the bright are falls into Zone VIII, which will be almost completely white in the finished picture.

Normal development
The zone system uses the terms plus, normal, and minus development. Normal development is used when you are satisfied with the zones the different areas of the object fall into. If, in our example, You were happy for the bright area to fall into Zone VIII, You can develop as normal. Normal development produces a good average contrast suitable for pictures taken in light that is neither unnaturally soft nor harsh.
What constitutes a normal development time is decided by calibration or experience. You will take a closer look at calibration in Part Four.

Normal development. The contrast of the object corresponds with the zone scale. You are content with the result and do not have to adjust the development.


Minus development
If, on the other hand, You are not satisfied with the way the other details fall, You will have to adjust the contrast. Assume that You do not want the bright area to fall into Zone VIII as being too white, and that You would prefer to have it in Zone VII. If this is the case, You want to reduce the picture's contrast. To do this You use minus development, and since You want to adjust the detail down one stop, You do a minus 1 development. You could also achieve the same reduction by printing onto a softer paper.

Minus development. The contrast of the object do not corresponds with the zone scale. The contrast is too high and needs to be reduced. Zone VIII in the object has to be moved down to zone VII on the scale. You will have to reduce the development. A minus 1 development is a proper development in this case.

Plus development
Equally well, You can find ourselves in a situation where You need to increase the contrast. Perhaps the light when You took the picture gave too low a contrast, leaving us with soft negatives and pictures as a result. Alternatively, the contrast in the picture is low simply because the object was low-contrast.
You will notice this when you measure the object with a spot meter. The exposure is chosen by measuring the darkest parts of the object, and placing the dark detail in the corresponding zone. When we measure the other details You may discover that they fall in too low a zone, resulting in a low-contrast picture. If, for example, we want to move a detail from Zone VI to Zone VIII, it means a two-stop move, and thus a plus 2 development. Later, You will take a closer look at how you calibrate exposure and development more precisely.

Plus development. In this case You are going to move zone VI in the object, up to zone VIII, in order to get the result You have visualized. Two stops up calls for a plus 2 development.