Zone system Development Test

Simply stated, in black and white photography exposure determines density and development determines contrast.

Exposure controls the amount of density in dark tones of the scene (zones I-IV. Its effects are felt equally across the tonal range. A one-stop exposure increase will raise the density readings 0.3 in the low zones as well as the higher ones.

Development controls contrast or the difference in density between the zones at the lower end of the tonal range and those at the higher end. Overall contrast is the difference between the lowest printable density (zone iii) and the highest (zone viii). Printing contrast is the rate of change between individual densities in the image.

The goal in determining the normal film developing time is to keep the brightest highlight (usually zone viii) printable and at the proper pre-visualized relative brightness.

Normal Contrast and Development

An average normal contrast subject has a brightness range of 7 to 7½ stops between the lightest and darkest areas of the scene, this does not include specular reflections and light sources in the photo. Normal contrast subjects have a brightness range of about 5½ stops between the areas you would place on zone iii (the darkest tone with detail) and those you would place on zone viii (the lightest tone with detail). The darker or lighter areas in the print, zones I, II, and IX will appear as shapes with tone but without detail. A negative could be considered normal contrast if a full range scene prints on grade two paper without any dodging or burning. In terms of density measurements a normal contrast negative has:

Zone I density of FBF + 0.10 to 0.15

Zone VIII density of FBF +1.00 using a condenser enlarger

Zone VIII density of FBF +1.20 using a diffusion enlarger or contact printing

Normal development otherwise called N produces a full range negative as defined above. A low contrast subject has a compressed brightness range 6 stops or less to print well the negative density range should be increased by more development, called normal plus or N+. A high contrast scene, one with an 8 stop range needs decreased development called normal minus or N-, so to produce a full range negative. When discussing development the number of zones a tone is shifted + or - will follow the development notation. (E.g. N+1, N+2, N-1, etc)

Making Test Exposures

Set up a target, white, gray or any medium color will do. It should be large enough to fill the frame from six feet away. The target should be smooth - wrinkles can cause shadows or uneven brightness.
Light the target evenly. Meter readings in the center and at the edges should not vary more than 1/3 of a stop.
Set your meter your true film speed or EI. Not the manufacture’s speed.
Take a reflected meter reading of the target; choose a shutter speed that will allow you to bracket without using the slowest or fastest speeds.
Set your camera for manual exposure; any auto-exposure setting will make the test meaningless.
Record your exposures as you make them.
Make the following exposures

Meter reading - Zone V

Blank frame - FB+F film base plus fog

4 stops less than the meter reading -Zone I to double check the film speed

1 stops more than the meter reading - Zone vi

2 stops more than the meter reading - Zone vii

3 stops more than the meter reading - Zone viii

4 stops more than the meter reading - Zone ix

5 stops more than the meter reading - Zone x

Develop the film normally. Using the developer, time temperature you usually use.

Evaluating the test

To get the true normal developing time you must determine which test exposure produces Zone viii. There are two ways to do this: you could make a visual determination by judging prints or you could use a densitometer. The densitometer is more accurate but you need to have access to the equipment.

The Densitometer Method

Take a reading of the blank frame (exposure b)

Take readings of all other frames; the frame with 1.0 more density (or 1.2 more if you are print with a diffusion enlarger) than the blank frame (b) the true zone viii

If test frame f is the true zone viii you developed the film normally.

If test frame e is the true zone viii you over developed the film N+. Repeat the test with but give it the film 15% less development.

If test frame g is the true zone viii then you underdeveloped the film N-. Repeat the test but give the film 15% more development.

Save your data. They may provide clues as to what N+1 or N-1 may be.

For example: You tested Kodak Tri-x, your EI is 200 and the blank frame (c) reads 0.23 and you print with a condenser enlarger

Frame e reads 1.43

Frame f reads 1.25

Frame g reads 1.15

Frame e is 1.02 above FBF so you developed the film normally

The Visual Method

Print a test strip from the blank frame

From the test strip choose the shortest exposure that turns the paper maximum black. If your not sure what maximum black looks like compare your test to a piece of paper that has been exposed to white light then developed.

Print frame c -zone I- if it does not print a tone that is just a bit lighter than maximum black you must redo the test because you did not expose the film properly.

Print frames e zone vii, f zone viii, g zone ix, on separate pieces of paper. Before making the exposure mark the frame id on the back of your test print. Then mark an ‘x’ on the left side of the emulsion side of the paper. Cover the marked side of the print with a piece of cardboard during the exposure. This is so you will have a sample of the white paper base near your test print.

Make your exposures but do not develop them. Put them in a light tight box for safe keeping

Develop all test print together; stop, fix, wash and dry them before judging the tones. Most papers will dry darker.

Look for the sample that that shows a distinctly different tone than paper base white.

If frame f zone viii shows the proper tone you developed the film normally

If frame e zone vii produces the required tone then you overdeveloped the film. N+. Repeat the test with but give it the film 15% less development.

If frame g zone ix shows the proper tone then you underdeveloped the film N-. Repeat the test but give the film 15% more development.

The Practical Method

This method is not as scientific or accurate as the densitometer tests however it works. You will need a gray card for this method

Choose an evenly lit stationary subject of normal contrast. (i.e. one with a five stop range between zone ii and zone viii). Place a gray card in the scene.
Set your meter at the EI you determined in the film speed test.
Meter and place zone iii tones 2 stops lower than the meter reading; choose a shutter speed that will allow you to bracket without using the slowest or fastest speeds.
Set your camera for manual exposure; any auto-exposure setting will make the test meaningless.
Record your exposures as you make them.
Make the following exposures.

Blank frame - FB+F film base plus fog
5 stops less thank the determined reading. (close down the lens, you may need to increase the shutter speed don’t forget to put it back at your original setting as soon as possible) - Zone 0
4 stops less than the determined reading -Zone I
3 stops less than the determined reading - Zone II
2 stops less than the determined reading - Zone III
1 stop less than the determined reading - Zone IV
Determined reading - Zone V
1 more than the determined reading –Zone VI
2 more than the determined reading –Zone VII
3 more than the determined reading –Zone VIII
4 more than the determined reading –Zone IX
5 more than the determined reading –Zone X

Repeat the bracket several times.

Develop the film normally. Using the developer, time temperature you usually use.

Evaluating the test

Contact the film or print each frame for the minimum time it takes to reach maximum black. Choose the frame where the zone viii tones are correctly represented.

If in frame g – zone Viii is correct then your developing time is correct.

If in frame h – zone Viii is correct then your film needs about 15% more development

If in frame f – zone Viii is correct then your film needs about 15% less development.

Finding N+ and N-developing times

Development that is more than normal (N+1) or less than normal (N-1) moves tones up or down the gray scale. The higher the exposures step the greater the movement. An area that produces a zone ix will move farther than an area that produces a zone vi. This is because unlike exposure development does not affect the tones in a linear fashion. The measurable amount of change is relative to the film and developer combination. . N+1 expands the printable tonal range of the negative, N-1 contracts it. Generally speaking modern films can be expanded or contracted up to two stops without objectionable changes to the midtones or the grain. However this should not prevent you from making greater changes based upon your previsualization. Rules are meant to be broken.

To plan accurate N+ or N- development you must test each film/developer combination. It is not advisable to extrapolate your results to different films or developers due to the fact that not all developers act on film the same way.

Test Exposures

Expose sets of test frames on one or more rolls of film. You will need at least three sets; more are better. You can fit three sets of exposures on a 36 exposure roll by exposing frames 1-7, 15-21, 29-35. Leave the rest blank.

Set up the test target as described above; set your camera for manual exposure and the ISO in your reflected light meter to your EI. Make and record your exposures as follows:

Meter reading zone v

Blank frameFB+F

Meter reading - 4 stops zone I to double check the film speed

Meter reading + 1 stop zone vi

Meter reading + 2 stop zone vii

Meter reading + 3 stop zone viii

Meter reading + 4 stop zone ix

Meter reading + 5 stop zone x

Development

Open the cassette and cut the sets of exposures apart. If you have a 36 exposure roll then loop it into thirds and cut between them. Identify the clips before you load them on the developing reels, use a ticket punch to make 0,1,2,3,4 holes in the clip end.

Using fresh developer develop each clip for a different amount of time:

20% less than the normal

Normal

20% more time

At the proper intervals and in the dark remove the top reel. Dropping each one into stop bath and then fixing. If you do not use stop then rinse as you normally would.

Please note. It is very important to completely fill the tank with chemistry and to use the total number of reels that the tank can hold even if one or two reels are empty. This will help you eliminate uneven agitation by controlling the amount of air in the tank and preventing the reels from sliding to and fro as you invert the tank.

The Densitometer Method

Evaluating the test

Using a densitometer read frame f, (zone viii) from the Normally developed clip. Check to be sure that it is 1.00 - 1.10 (assuming your aiming for condenser enlarger specs; 1.20 - 1.30 for the diffusion type) more than the FB+F reading. This reading will become your reference reading. Read the densities of frames b-f on the remaining clips and compare them to the reference

If a (x) frame on any given clip reads:

Frame e -zone vii is equal to the reference frame, then that clip was developed for N+1

Frame d -zone vi is equal to the reference frame, then that clip was developed for N+2

Frame g -zone ix is equal to the reference frame, then that clip was developed for N-1

Frame h - zone x is equal to the reference frame, then that clip was developed for N-2

For example

Your reference frame reads 1.32

Frame g = 1.32

This means the clip was developed for N-1. Whether you developed it 20% or 15% less your normal time is not as important as the fact that this will be the time you use when developing film containing scenes with extended brightness range (8 - 10 stops).

If frame h = 1.30 then your test clip would have been developed for N-2.

If the test results do not match the reference frame zone viii, estimate how much more or less development is required and repeat the test.

The Visual Method

Print a test strip from the blank frame (b)
From the test strip choose the shortest exposure that turns the paper maximum black. If your not sure what maximum black looks like compare your test to a piece of paper that has been exposed to white light then developed.
Print frame c -zone I- if it does not print a tone that is just a bit lighter than maximum black you must redo the test because you did not expose the film properly.
Print frames: d zone vi, e zone vii, f zone viii, g zone ix, h zone x, on separate pieces of paper. Before making the exposure mark the frame id on the back of your test print. Then mark an ‘x’ on the left side of the emulsion side of the paper. Cover the marked side of the print with a piece of cardboard during the exposure. This is so you will have a sample of the white paper base near your test print.
Make your exposures but do not develop them. Put them in a light tight box for safe keeping
Develop all test print together; stop, fix, wash and dry them before judging the tones. Most papers will dry darker.
Look for the first sample that that shows a distinctly different tone than paper base white.

If frame d zone vi shows the proper tone then that clip was developed for N+2

If frame e zone vii produces the required tone then that clip was developed for N+1

If frame f zone viii shows the proper tone you developed the film normally

If frame g zone ix shows the proper tone then that clip was developed for N-1

If frame h zone x shows the proper tone then that clip was developed for N-2

The Practical Method

This method is not as scientific or accurate as the densitometer tests however it works. You will need a gray card. You must repeat this test for every contrast type for which you wish to find a developing time.

Choose an evenly lit stationary subject of x contrast. (i.e. N+1 is one with a 4 stop range between zone iii and zone viii, N-1 is one with a 6 stop range between zone iii and zone viii,). Place a gray card in the scene.
Set your meter at the EI you determined in the film speed test.
Meter and place zone iii tones 2 stops lower than the meter reading; choose a shutter speed that will allow you to bracket without using the slowest or fastest speeds.
Set your camera for manual exposure; any auto-exposure setting will make the test meaningless.
Record your exposures as you make them.
Make the following exposures.

Blank frame - FB+F film base plus fog

5 stops less thank the determined reading. (close down the lens, you may need to increase the shutter speed don’t forget to put it back at your original setting as soon as possible) - Zone 0

4 stops less than the determined reading -Zone I

3 stops less than the determined reading - Zone II

2 stops less than the determined reading - Zone III

1 stop less than the determined reading - Zone IV

Determined reading - Zone V

1 more than the determined reading –Zone VI

2 more than the determined reading –Zone VII

3 more than the determined reading –Zone VIII

4 more than the determined reading –Zone IX

5 more than the determined reading –Zone X

Develop the film accordingly; N+1 requires about 15% more time than the normal you found in the previous test.

Evaluating the test

Contact the film or print each frame for the minimum time it takes to reach maximum black.

Choose the frame where the zone viii tones are correctly represented.

If in frame g – zone Viii is correct then your developing time is correct.

If in frame h – zone Viii is correct then your film needs about 15% more development.

If in frame f – zone Viii is correct then your film needs 15% less development

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