Overview
ISO 1755:1987 specifies the essential dimensions and basic requirements for projector slides of three preferred international sizes: 3 cm × 3 cm, 5 cm × 5 cm and 7 cm × 7 cm. The standard was prepared by ISO/TC 42 (Photography) and is intended to facilitate manufacture, handling, use and international interchangeability of projector slides while minimizing the proliferation of incompatible sizes.
Key scope notes from the standard:
- Applies to standard projection slides intended for optical projection by transmitted light.
- Does not apply to "sub-miniature" slides smaller than 3 cm × 3 cm or to slides for specialized uses such as television.
- Provides dimensional, geometric and marking guidance to support interoperability.
Key Topics
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Nominal sizes and overall dimensions: ISO 1755 defines overall slide dimensions for the three nominal sizes to promote interchangeability between mounts and projectors.
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Picture area: The standard references the nominal picture area (for example, the common 13 mm × 17 mm area associated with certain film formats) and requires the picture area to be centrally located in the mask aperture.
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Title strip: A title strip, when used, shall be a light-coloured strip at least 3.0 mm wide along the upper margin when the slide is correctly oriented. The strip may extend onto the upper edge but must not extend onto the back.
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Mask aperture and centering: Mask apertures must be horizontally and vertically centred on the slide. Distances from opposite slide edges to the aperture edges must not differ by more than 0.5 mm. Corners of the mask aperture are specified to be right-angled within a tolerance of +1°.
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Squareness and edge radii: Adjacent sides of the slide mount shall be mutually at right angles within a tolerance of +1°. Slide mount corners are recommended to be rounded to a radius of not more than 2.5 mm, and peripheral edges should be sharp or rounded to a radius not exceeding 0.3 mm.
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Thickness and compatibility: The standard provides thickness limits for each nominal slide size (listed in the standard table). A note cautions that certain automatic slide changers may not accept all thicknesses within the specified range.
Applications
ISO 1755:1987 is useful for:
- Manufacturers of slide mounts, film carriers, and projection accessories seeking dimensional compliance for global markets.
- Laboratories and service providers producing mounted slides for presentations, education, archives and exhibitions.
- Equipment designers (projectors, automated slide changers) who need to ensure mechanical compatibility and smooth handling.
- Archivists and conservators standardizing collections to prevent handling and projection issues.
Benefits include improved interchangeability, reduced production variation, and clearer expectations for title-strip placement and mask alignment.
Related Standards
- ISO 1203 - Photography: roll film cameras - back window location and picture sizes.
- ISO 1754 - Photography: cameras using 35 mm and smaller film - picture sizes.
- ISO 7374 - Photography: 710-size cartridge - dimensions and format of film and backing paper.
For precise numeric values (complete tables of overall sizes, mask apertures and thickness ranges) refer to the full ISO 1755:1987 document. This overview highlights the practical requirements and interoperable design considerations defined by the standard.
