T Number
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T Number
T Number, also known as the ASA (American Standards Association) rating, is a measure of the sensitivity of photographic film to light. It is a logarithmic scale that indicates the amount of light required to produce a given level of density on the film. The higher the T Number, the more sensitive the film is to light. This system was developed by the German photographic company Agfa in 1937 and has since become the standard for measuring film sensitivity. The T Number system has been widely adopted by film manufacturers around the world, including Kodak and Fujifilm. It allows photographers to choose the appropriate film for a given situation based on the amount of available light and desired level of detail. For example, a higher T Number film would be suitable for low-light conditions or fast-moving subjects, while a lower T Number film would be better for bright, well-lit scenes. The T Number system has also had a significant impact on the art of photography. It has allowed photographers to capture images with greater clarity and detail, and has enabled them to experiment with different lighting conditions and techniques. Some of the most iconic works of photography, such as Ansel Adams' Moonrise, Hernandez and Edward Weston's Nautilus, were created using the T Number system. In recent years, the use of film has declined as digital photography has become more popular. However, the T Number system remains relevant for those who continue to use film or who wish to learn about the history and techniques of traditional photography.
photographic film, sensitivity, logarithmic scale, Agfa, Kodak, Fujifilm, low-light conditions, clarity, detail, lighting techniques, digital photography
CITATION : "Kevin Harris. 'T Number.' Design+Encyclopedia. https://design-encyclopedia.com/define/t-number?E=322943 (Accessed on October 14, 2026)"
T Number
T Number is a system of rating light sensitivity of photographic film. It is the logarithmically calculated value of the exposure (in lux-seconds) required to produce a specified density (optical density) on the film. This system was developed by the Germany photographic company Agfa in 1937 and it is still in widespread use today, with Kodak and other manufacturers using their own variations of the system. Works of art by notable photographers such as Ansel Adams (Moonrise, Hernandez) and Edward Weston (Nautilus) reflect the success of the T Number system in producing a level of sharpness and clarity that has since become iconic.
Photo, photography, film, exposure, lux-seconds, Agfa, Kodak, Ansel Adams, Edward Weston, optical density, sharpness, clarity.
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