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A patent application showing a new mirror lens design from Canon is confusing to say the least. I figured the days of the catadioptric lens were well behind us, but here we are.</p>
<p><span class="notranslate"><strong>Specification from the patent:</strong></span></p>
<ul>
<li><span class="notranslate">Focal length: 400mm</span></li>
<li><span class="notranslate">Aperture: f/5.6</span></li>
<li><span class="notranslate">2 ω: 1.96</span></li>
<li><span class="notranslate">Image height: 13.66mm</span></li>
<li><span class="notranslate">Back focus: 33.07mm</span></li>
<li><span class="notranslate">Lens length: 247.73mm</span></li>
</ul>
<p>The <a href="http://www.northlight-images.co.uk/canon-ef-lenses-rumours-and-news/">image below from Northlight</a> shows the light path through the lens. The light path is in red, and the mirrors are outlined in blue and labelled.</p>
<blockquote><p>The blue bits are mirrors. The light comes in through L1, bounces off M1/M2 and through a hole in M1 back to the camera.</p></blockquote>
<p><a href="http://www.canonrumors.com/forum/index.php?topic=34076.msg698929#msg698929">neuroanatomist on the forum</a> thinks this could be an EF-M mount lens. You can view the patent at the Japanese Patent Office <a href="https://www.j-platpat.inpit.go.jp/web/PU/JPA_H29219642/E2F2B7A25E23CBF08049D831B95527EF">here</a>.</p>
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