Editing Film speed (section)

====GOST{{anchor|GOST 2817|GOST 10691}}====
<!-- This section is linked from inside or outside this article, preferable by "#GOST". Do not rename without keeping in sync. -->
[[File:Svema-film-65.jpg|thumb|A box of [[Svema]] film, with a sensitivity of 65 [[GOST]] (ГОСТ)]]
{{lang|ru-Latn|[[GOST]]|italic=no}} (Cyrillic: {{lang|ru|ГОСТ}}) was an arithmetic film speed scale defined in GOST&nbsp;2817-45 and GOST&nbsp;2817–50.<ref name="Gorokhovskiy_1970_Metrologiya"/><ref name="GOST_2817-50"/> It was used in the former [[Soviet Union]] since October 1951,{{Citation needed|date=August 2011}}<!-- TBD: Why not earlier when GOST 2817-45 was defined earlier? --> replacing Hurter & Driffield (H&D, Cyrillic: ХиД) numbers,<ref name="Gorokhovskiy_1970_Metrologiya"/> which had been used since 1928.{{Citation needed|date=August 2011}}

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&nbsp;0.1.<ref name="Stroebel_1993_Encyclopedia"/> GOST markings are only found on pre-1987 photographic equipment (film, cameras, [[Light meter|lightmeters]], etc.) of Soviet Union manufacture.<ref name="ZENIT_2011_GOST"/>

On 1 January 1987, the GOST scale was realigned to the [[#ISO|ISO]] scale with GOST&nbsp;10691–84,<ref name="GOST_10691-84"/>

This evolved into multiple parts including GOST&nbsp;10691.6–88<ref name="GOST_10691.6-88"/> and GOST&nbsp;10691.5–88,<ref name="GOST_10691.5-88"/> which both became functional on 1 January 1991.<!-- Also found "GOST 10691-63" and various other GOST 10691.x-xx variants. -->