Abridgment: Safety Factors in Camera Exposures

Metadata

Publisher: SMPTE — White Plains, NY, USA
Doc Type: Journal Article
Content Type: Original Research
Abbreviated Title: J SMPTE
Volume: 69, No. 7, pp. 479–483
Abstract: A new American Standard for determining the speeds of black-and-white negative films for still cameras was issued in April 1960 by the American Standards Association. The new speeds are approximately twice the exposure indexes defined by the older version of the Standard. The level of the numbers was increased in order to reduce the “safety factor” in camera exposures indicated by exposure meters. The reduced exposures give negatives that are better from the standpoint of ease of printing, sharpness, and print graininess. The present paper is a report on a study, made in connection with this standardization project, to determine the absolute magnitude of the safety factor. Both the mathematical and experimental parts of this study indicate that the safety factor associated with the exposure index is approximately 2.4 for average sunlit scenes when accurate meters, shutters and lens apertures are used. The safety factor associated with the new ASA speed is slightly more than 1.2, the same as for color reversal films. The revised speed criterion and the new additive system of units for film speed, scene light, lens aperture and shutter speed are described.
Publication Date: 1960-07-01
DOI: 10.5594/J15590
ISSN: Print: 0361-4573
Link: https://doi.org/10.5594/J15590
Author(s): C. N. Nelson
Copyright: © 1960 Society of Motion Picture and Television Engineers, Inc.

Bibliographic Reference(s)

1. American Standard for Determining Photographic Speed and Exposure Index, PH2.5- 1954 , American Standards Association, 10 East 40 St., New York 16. EXTERNAL
2. American Standard for Photographic Exposure Meters, Photoelectric Type, PH2.12, American Standards Association. EXTERNAL
3. Varden Lloyd E. , “ASA exposure index: Dangerously safe,” PMI (Photo Methods for Industry) , 1 : 39 , May 1958 . EXTERNAL
4. American Standard Method for Determining Speed of Photographic Negative Materials (Monochrome, Continuous-Tone), PH2.5- 1960 , American Standards Association, 10 East 40 St., New York 16. EXTERNAL
5. Jones L. A. Condit H. R. , “Sunlight and sklylight as determinants of photographic exposure,” J. Opt. Soc. Am. , 38 : 123 , 1948 ; 39: 94, 1949. EXTERNAL
6. Nelson C. N. Simonds J. L. , “Simple methods of approximating the fractional-gradient speeds of photographic materials,” J. Opt. Soc. Am. , 46 : 324 , 1956 . EXTERNAL
7. Goldsmith Arthur , “A new language for photography,” Popular Photography , 46 : Feb. 1960 . EXTERNAL

Source Data (JSON)

Full registry record with provenance metadata. Open directly: /api/doc/10.5594-J15590.json

Reference Tree

Explore all references and references to this document, as a navigable tree.

Open Reference Tree

Reference this Doc

Plain text (ISO 690 compliant)

Preview:

C. N. Nelson; Abridgment: Safety Factors in Camera Exposures, Journal of the SMPTE ( Volume: 69, Issue: 7, July 1960); SMPTE, 1960. Available at https://doi.org/10.5594/J15590

Snippet:

C. N. Nelson; Abridgment: Safety Factors in Camera Exposures, Journal of the SMPTE ( Volume: 69, Issue: 7, July 1960); SMPTE, 1960. Available at https://doi.org/10.5594/J15590

HTML (ISO 690 compliant)

Preview:

C. N. Nelson; Abridgment: Safety Factors in Camera Exposures, Journal of the SMPTE ( Volume: 69, Issue: 7, July 1960); SMPTE, 1960. Available at https://doi.org/10.5594/J15590

Snippet:

<span class="citation">C. N. Nelson; <cite>Abridgment: Safety Factors in Camera Exposures</cite>, Journal of the SMPTE ( Volume: 69, Issue: 7, July 1960); SMPTE, 1960. Available at <a href="https://doi.org/10.5594/J15590" target="_blank" rel="noopener">https://doi.org/10.5594/J15590</a></span>

SMPTE's HTML Pub

Preview:

C. N. Nelson; Abridgment: Safety Factors in Camera Exposures, Journal of the SMPTE ( Volume: 69, Issue: 7, July 1960); SMPTE, 1960
doi: 10.5594/J15590
url: https://doi.org/10.5594/J15590

Snippet:

<li>
C. N. Nelson; <cite id="bib-10-5594-j15590">Abridgment: Safety Factors in Camera Exposures</cite>, Journal of the SMPTE ( Volume: 69, Issue: 7, July 1960); SMPTE, 1960
<span class="doi">10.5594/J15590</span>
</li>

Referenced By

Progress Committee Report for 1961 [Active]