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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Optical format</span></span>
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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="en" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><p><b>Optical format</b> is a hypothetical measurement approximately 50% larger than the true diagonal size of a <a href="Solid-state_(electronics)" class="mw-redirect" title="Solid-state (electronics)">solid-state</a> <a href="Photo_sensor" class="mw-redirect" title="Photo sensor">photo sensor</a>. The use of the optical format means that a lens used with a particular size sensor will have approximately the same angle of view as if it were to be used with an equivalent-sized <a href="Video_camera_tube" title="Video camera tube">video camera tube</a> (an "old-fashioned" TV camera). In a video camera tube, the diagonal of the actual light-sensitive target was about two-thirds the outside diameter, which was the measure used.
</p><p>The optical format is approximately the diagonal length of the sensor multiplied by 3/2. The result is expressed in inches and is usually (but not always) rounded to a convenient fraction. For instance, a 6.4x4.8<span class="nowrap"> </span>mm sensor has a diagonal of 8.0<span class="nowrap"> </span>mm and therefore an optical format of 8.0*3/2 = 12<span class="nowrap"> </span>mm, which is expressed as <style data-mw-deduplicate="TemplateStyles:r1154941027">
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</style><span class="frac"><span class="num">1</span>⁄<span class="den">2</span></span> inch in <a href="Imperial_units" title="Imperial units">imperial units</a>. The reason it is expressed in inches is historical, dating back to the early days of television. <sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>
</p><p>Many image device sheets do not list the actual optical format but do list the size of their pixels in terms of micrometers; a helpful equation can be used to convert the pixel size and array size directly to optical format. The equation for this is:
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle OF={\frac {p{\sqrt {w^{2}+h^{2}}}}{16000}}}">
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<mrow class="MJX-TeXAtom-ORD">
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<mi>O</mi>
<mi>F</mi>
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<mi>p</mi>
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<mi>w</mi>
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<mn>2</mn>
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<mi>h</mi>
<mrow class="MJX-TeXAtom-ORD">
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<mn>16000</mn>
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<annotation encoding="application/x-tex">{\displaystyle OF={\frac {p{\sqrt {w^{2}+h^{2}}}}{16000}}}</annotation>
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</math></span><img src="./0d8db9b08708164c0f2a970a35abb73517370701.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:18.894ex; height:6.176ex;" alt="{\displaystyle OF={\frac {p{\sqrt {w^{2}+h^{2}}}}{16000}}}" loading="lazy"></span></dd></dl>
<p>with:
</p>
<ul><li>w = width of array (in pixels)</li>
<li>h = height of array (in pixels)</li>
<li>p = pixel size (micrometers)</li></ul>
<div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2></div>
<ul><li><a href="Image_sensor_format" title="Image sensor format">Image sensor format</a></li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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<li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external free" href="http://www.dpreview.com/news/2002/10/7/sensorsizes">http://www.dpreview.com/news/2002/10/7/sensorsizes</a> (table of sensor sizes at bottom)</span>
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