The processing required to produce a quality product of any particular film varies with different developer and film combinations, time and temperature of the process, agitation, the film exposure, and the skill of the darkroom worker. A good, high-quality image is one that is free from all processing faults, including scratches and dirt, and so forth.

When processing black-and-white film, your goal is to produce a normal negative that is as fault-free as possible. Normal is a rather vague term; however, a normal negative is one that yields a pleasing print or reproduction of the original scene when printed without a printing filter or with a No. 2 printing filter.

When film is exposed and processed properly, it is a normal negative. However, when a negative varies from normal, you should be able to determine what conditions caused the deviation.

A negative has several basic characteristics to consider when evaluating quality. These basic characteristics are as follows:

General negative density or opacity to light.

Image highlights or areas of greatest density.

The shadows or areas of least density.

Contrast or the differences between highlight and shadow densities.

Tonal gradation or the range of grays between the highlights and the shadows.

Graininess or the appearance of silver grains in a clumps determines the degree of graininess in the processed material.

All the basic characteristics of a negative are affected to some extent by a combination of exposure and development. By studying these characteristics, you can usually determine the cause of an error or poor quality in a negative.

DENSITY

Density determines how much of the incident light falling upon a negative passes through the image. When a small amount of silver is present in the negative, the image appears thin (transparent), and it has low density. When there is a large amount of silver present, only a small amount of light passes through the image, and the negative is said to have high density.

A low density, thin negative can be caused by underexposure or underdevelopment or by a combination of the two. A heavy or dense negative is the result of either overexposure or overdevelopment or a combination of the two.

HIGHLIGHTS

The highlights, or dark areas, of a negative for most purposes should not lack detail. When detail is lacking because the highlights are too dark, the highlights are too dense or blocked up. Excessive highlight density is caused by overexposure and/or overdevelopment. When both the highlights and the shadow areas are too thin and lack detail, the negative is probably underexposed. Thin highlights are caused by

underexposure and/or underdevelopment.

This may seem like a repetition of the previous discussion on density. However, a negative could and may have overall good density except in the highlight areas. This situation is a result of exposure latitude that is not great enough for the scene brightness range.

SHADOWS

The shadows, or the more clear areas of the negative, also should contain image detail. If these areas are so thin and weak that they are transparent or nearly so, the shadow areas are said to be lacking in detail. Loss of shadow detail is caused normally by underexposure.

The need for detail in both the highlights and the shadows for photographs of most subjects cannot be stressed too strongly. One is as important as the other in the production of good photographs.

CONTRAST

Contrast is the difference in density between the highlights and the shadows in a negative. When this difference is great, the negative is said to be contrasty. When the density difference is small, the negative is said to be flat or lacking in contrast.

For a negative to have normal contrast, the density differences between the highlight and shadow areas of the negative must be proportional to the reflective brightness range of the subject photographed

A contrasty negative usually is the result of overdevelopment but also may be caused by a high scene lighting ratio (a contrasty original scene). A flat negative, on the other hand, may be caused, primarily, by underdevelopment or a low-contrast original scene.