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Zone SystemChapter 5 Film Development and Density

Film density

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What is film density?

Black and white negatives usually have some dark areas and some clearer areas. Film Density is a measure of thedarkness or opacity of the film at a given area of the negative.

There is a correlation between the range of film density on a negative and the way the negative prints on a paper ofany given contrast. There are other complicating factors too. Let's start with something you can measure with a

light meter. If you take a sheet of photographic paper, expose half of the paper to a strong light white light but keep

the other half unexposed, then develop the paper fully, you will have a piece of paper that is half black and half

white. If you measure the one side then measure the other side using a light meter, you will find that the paper

reflects roughly 5 F-stops more light from the white side than the dark side. Common sense will allow you to see

that no matter how great the range of light in the original subject you choose to photograph, the reproduction is

going to be limited to the range of light between the light side and the dark side of the paper you print on. These

two print values are known as Dmax and Paper base White or occasionally Dmin.

Introducing The Abominable Snowman to the picture

Suppose you have a negative that prints perfectly on a certain paper. Imagine that the original subject had no pure

white areas in it -- just a range of grays from very dark to pretty light. Let's also say that you developed the film for

9 minutes in your favorite developer. When you print the negative, everything just works out perfectly. You have

nice rich shadow values and nice open detailed highlights. The film and your paper are working together perfectly.

Okay, now suppose that at the moment of exposure the abominable snowman, dressed in a white tux, suddenly

jumped into the middle of a shaft of light in the middle of your picture. Now you have a valuable image in your

camera. Wow, the abominable snowman, you'll be famous! If you take the film back to your lab and develop it for

the same 9 minutes that was working for the picture before, you will get a negative that prints great, just like

before -- except in the area of the abominable snowman. The darn thing, under similar printing conditions you were

previously using, is going to be just a big award-losing white blob in the print. The reason is that Abby reflected abunch more light than the rest of the image and therefore made a big dense blob on your negative that is going to bedifficult to print.

We have faith in you. You'll find a way to print the negative and achieve the rewards of capturing Abby on film.For now, just imagine that printing the film will be more difficult because you now have some areas that are too

dense for your normal printing techniques.

The thing that is really happening is that the range of film densities is too great for your normal paper to handle

effortlessly. A typical grade 2 paper (Normal contrast) likes to print a negative that has a density range of about 1.5

between very dark areas and very light areas. If your negatives have that sort of density range, they'll print readily

on papers of normal contrast.

The table below gives a bit more detail and descriptions about 11 points along the gray scale. These points are

given the names Zone 0, Zone 1,Zone 2, Zone 3, Zone 4, Zone 5, Zone 6, Zone 7, Zone 8, Zone 9 and Zone 10.

Their definitions are basically the information in the chart below ( also found elsewhere on this server). Some

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thinkers divide the gray scale differently using more than 11 key points, or less than 11, or 11 but different ones.These are the key points as described by Ansel Adams in his bookThe Negative. The film densities represented

here are from independent testing done by one of my students under my supervision.

This particular way of dividing the gray scale into 11 named areas turns out to be exceptionally photographically

convenient. In addition to using this web site, you should get a copy ofThe Negative by Ansel Adams and read itcarefully. Then reread it. That is the book for anyone seriously interested in the Zone System. Before using any

other volume for reference material I suggest that you look at the photographs actually created by the authors and

compare them to Adams' photographs. Then if you still are tempted away from Adams's book, make 100% positivethat any other reference includes good writing about film testing, plus-and-minus development, pre-exposure of

film and more. Stick with Adams, you'll be better off in the end. Don't worry if the going is slow; it's worth it.

Table 5.1: Zone System Chart

Description, Textural Properties, Film Densities

ZoneZone

0

Zone

I

Zone

II

Zone

III

Zone

IV

Zone

V

Zone

VI

Zone

VII

Zone

VIII

Zone

IX

Zone

X

Descr.

ofprint

value

Dmax.

pureblack.

1st

perceptibl

e valuelighter

than

black.

very verydark gray

fully

textured dark

Gray

dark

middlegray

middle

gray 18%reflectance

light

middlegray

fully

texturedlight

Gray

very verylight gray

1st

perceptible

graydarker

than white

Dmin.

paperbase

white

Textur

e

none none suggestionof texture

fulltexture

fulltexture

fulltexture

fulltexture

fulltexture

suggestion

of texture

none none

Film

Density

.02 .11 .21 .34 .48 .62 .76 .97 1.18 1.33 1.44

Notes:

The figures above came from a series of tests performed by Martha Milsaps during the summer of 1991

(I think :-). Martha tested 35mm Kodak T-Max 100 film for printing on a condenser enlarger; I oversawthe test procedures and results. These figures may differ from your own; they represent appropriate film

densities for the particular equipment Martha was using in the darkroom. If you are using a different

film or are using a different enlarger, then you figures *should* be different from these. So do not worry

if your test results vary somewhat from these. Even so, these densities are an excellent representative set

that you can use as known good values to compare to your own film test results.

Next: Practical Implications of Film Density

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