Journal of the Society of Motion Picture Engineers ( Volume: 14, Issue: 5, May 1930)

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Measuring the Effective Illumination of Photographic Objectives

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Publisher: SMPTE
Doc Type: Journal Article
Article Type: research-article
Abstract: The photo-chemical action of light on the photographic plate depends on the light intensity and on the length of exposure, other conditions being constant. The brightness of the photographic image is proportional to the square of the ratio of the radius of the entrance pupil to the focal distance, or to the square of the relative aperture, which latter may be expressed by 1/n, where n = f/d (d is the diameter of the entrance pupil). The illumination afforded by a photographic objective is determined by its relative aperture, on purely geometric considerations. In this expression of the relative aperture, there is no factor expressing the light losses in the lens which decrease the effective illumination of objectives; for example, the losses caused by reflection at the lens surfaces, by absorption in the glass, and by absorption in the cementing material. If we designate by I<inf>0</inf> and I the intensities of illumination before and after passing through the objective, the true, effective brightness of a photographic objective is more accurately given by the expression.
Publication Date: 1930-05-01
DOI: 10.5594/J13063
Link: https://doi.org/10.5594/J13063
Author(s): J. Hrdlicka

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J. Hrdlicka; Measuring the Effective Illumination of Photographic Objectives, Journal of the Society of Motion Picture Engineers ( Volume: 14, Issue: 5, May 1930); SMPTE, 1930. Available at https://doi.org/10.5594/J13063

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J. Hrdlicka; Measuring the Effective Illumination of Photographic Objectives, Journal of the Society of Motion Picture Engineers ( Volume: 14, Issue: 5, May 1930); SMPTE, 1930. Available at https://doi.org/10.5594/J13063

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<span class="citation">J. Hrdlicka; <cite>Measuring the Effective Illumination of Photographic Objectives</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 14, Issue: 5, May 1930); SMPTE, 1930. Available at <a href="https://doi.org/10.5594/J13063" target="_blank" rel="noopener">https://doi.org/10.5594/J13063</a></span>

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<li>
J. Hrdlicka; <cite id="bib-10-5594-j13063">Measuring the Effective Illumination of Photographic Objectives</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 14, Issue: 5, May 1930); SMPTE, 1930
<span class="doi">10.5594/J13063</span>
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