page_title: Film speed
section_title: GOST
hierarchical_section_title: Film speed / Film speed measurement systems / Historical systems / GOST
caption_attribution_description: English: A photograph of the product packaging of a roll of Svema film
context_page_description: Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. A closely related ISO system is used to describe the relationship between exposure and output image lightness in digital cameras.
  Relatively insensitive film, with a correspondingly lower speed index, requires more exposure to light to produce the same image density as a more sensitive film, and is thus commonly termed a slow film. Highly sensitive films are correspondingly termed fast films. In both digital and film photography, the reduction of exposure corresponding to use of higher sensitivities generally leads to reduced image quality. In short, the higher the sensitivity, the grainier the image will be. Ultimately sensitivity is limited by the quantum efficiency of the film or sensor.
context_section_description: GOST (Cyrillic: ГОСТ) was an arithmetic film speed scale defined in GOST 2817-45 and GOST 2817–50. It was used in the former Soviet Union since October 1951, replacing Hurter & Driffield (H&D, Cyrillic: ХиД) numbers, which had been used since 1928.
  GOST 2817-50 was similar to the ASA standard, having been based on a speed point at a density 0.2 above base plus fog, as opposed to the ASA's 0.1. GOST markings are only found on pre-1987 photographic equipment (film, cameras, lightmeters, etc.) of Soviet Union manufacture.
  On 1 January 1987, the GOST scale was realigned to the ISO scale with GOST 10691–84,
  This evolved into multiple parts including GOST 10691.6–88 and GOST 10691.5–88, which both became functional on 1 January 1991.
caption: A box of Svema film, with a sensitivity of 65 ГОСТ
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