The majority of black-and-white films are engineered to produce a negative image in black silver. Specifically, the latent image captured in the camera is intensified into visible black silver during the development process, and the remaining creamy halides are removed, resulting in a negative image (where the subject’s highlights are darkest, and shadows are lightest) within clear gelatin.
General-purpose panchromatic films typically range from ISO 25/15° to ISO 3200/36°. Slower films are characterized by finer grain and superior detail resolution. Additionally, slower films tend to have slightly higher contrast—defined as the range of gray tones between the darkest black and complete transparency—than faster films. This characteristic is accounted for in recommended development times, which are generally shorter for slower films.
Films within the ISO 100/22° to ISO 400/27° range offer a favorable balance between speed and graininess. For example, ISO 400/27° film produces prints with a slightly noticeable grain pattern (especially in uniform gray areas such as the sky) when 35 mm negatives are enlarged beyond 10 × 8 inches, although this effect is influenced by negative development and the type of enlarger light source used.
Generally, it is advisable to use the slowest film that the subject conditions allow, particularly when working with small negatives such as 35 mm. For scenarios where long exposures are required to create motion blur in moving objects, slower film is advantageous.
However, using slow film might restrict the ability to stop down sufficiently for depth of field or necessitate the use of a tripod in impractical situations. Fast film becomes essential for reportage photography under low-light conditions, action subjects, or handheld telephoto lens shots requiring exceptionally short shutter speeds. Although reportage photographers might use flash in certain situations, allowing for slower film, this approach is unsuitable when the photographer wishes to remain inconspicuous. In well-lit conditions, if a grainy texture is desired using very fast film, an ND (neutral density) filter can be employed to reduce exposure.
Chromogenic films, such as Ilford XP2 Super and Kodak T400CN, produce their final image in a purple-brown dye rather than silver. These films contain extra components in the emulsion layers that form tiny dye globules wherever silver is developed. The processing of these films, known as ‘chromogenic,’ ultimately bleaches away all the silver, leaving the image solely in dye molecules. Given that the chemicals and processing stages are identical to those for color negatives, these films can be easily processed at any high-street mini-lab for quick black-and-white results.
An additional advantage of chromogenic films is their greater tolerance for inaccurate exposure, particularly overexposure, compared to silver image films. These films can be rated between ISO 125/22° and 1600/33°, with appropriate development. Despite their fine grain, the grain is less defined, and image sharpness is slightly inferior to silver image films. They also incur higher self-processing costs and lack the variety of developer options available for other films. Chromogenic films are favored by some news and documentary photographers due to their suitability for diverse shooting conditions and their distinct aesthetic compared to silver halide films.
