# Patent - EF 28 f/1.8 DO & Others



## Canon Rumors Guy (May 25, 2011)

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<strong> </strong></p>
<p><strong></p>
<div id="attachment_6592" class="wp-caption alignnone" style="width: 310px"><img class="size-medium wp-image-6592" title="24DO" src="http://www.canonrumors.com/wp-content/uploads/2011/05/24DO-300x133.png" alt="" width="300" height="133" /><p class="wp-caption-text">EF 28 f/1.8 DO</p></div>
<p></strong></p>
<p><strong>Canon files patent for new DO lenses

</strong></p>
<ul>
<li>Patent publication 2009-198960</li>
<li>Published 03/09/2009</li>
<li>Filing date 2008/02/25</li>
</ul>
<p><strong>Example 1</strong></p>
<ul>
<li>Focal length f = 27.14mm</li>
<li>Fno = 1.85</li>
<li>Angle of 77.1 Ã‚Â°</li>
</ul>
<p><strong>Example 2</strong></p>
<ul>
<li>Focal length f = 24.50mm</li>
<li>Fno = 1.45</li>
<li>Angle of 82.9 Ã‚Â°</li>
</ul>
<p><!--more--><strong>Example 3</strong></p>
<ul>
<li>Focal length f = 25.00mm</li>
<li>Fno = 1.45</li>
<li>Angle of 81.8 Ã‚Â°</li>
</ul>
<p><strong>Example 4</strong></p>
<ul>
<li>Focal length f = 24.33-36.50-47.00mm</li>
<li>Fno = 3.4-4.0-4.7</li>
<li>83.3-61.3-49.4 Ã‚Â° angle</li>
</ul>
<p><strong>Example 5</strong></p>
<ul>
<li>Focal length f = 26.00-39.00-50.23mm</li>
<li>Fno = 3.4-4.0-4.7</li>
<li>79.5-58.0-46.6 Ã‚Â° angle</li>
</ul>
<p><strong>Information</strong></p>
<ul>
<li>General retrofocus</li>
<li>In general SLR wide angle lens</li>
<li>Many chromatic aberration</li>
<li>Using high-dispersion glass, as excessive compensation around</li>
<li>General diffractive optics</li>
<li>Can correct chromatic aberrations</li>
<li>Where it is difficult to use</li>
<li>Manufacturing difficulties</li>
<li>Aberration can not fine-lattice</li>
</ul>
<p><strong>Patented Features</strong></p>
<ul>
<li>Adopted retrofocus</li>
<li>Chromatic aberration correction over the entire</li>
<li>Diffractive optical elements, aspherical and low dispersion, employing anomalous dispersion lens</li>
<li>The lenses focus mechanism</li>
<li>Front lens is fixed</li>
<li>Second lens to focus</li>
<li>Floating mechanism</li>
<li>The optical system of patents</li>
<li>Lateral chromatic aberration to occur around the first lens</li>
<li>Not easily corrected by increasing the number of lenses</li>
<li>Diffractive optics correction to put the image side than the diaphragm</li>
<li>Only increase the power of the diffractive optical element</li>
<li>Chromatic aberration correction using a bonded lens</li>
</ul>
<p>This is an older patent application, but I think itâ€™s still important to see diffractive optics are not dead within Canon R&D.</p>
<p><strong><span style="color: #ff0000;">c</span>r</strong></p>
<p><strong> </strong>
```


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## jsixpack (May 25, 2011)

well that is a messy translation!

If the DO optics could make the lens smaller, I think this could be a big win. People are seeing the "pancake" lenses on the m4/3 cameras and are probably wondering where one is for the big boys...

just my thought, otherwise the current f1.8 is an excellent lens, has modern USM, all the normal goodness

JSP


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## Justin (May 25, 2011)

Canon Rumors said:


> This is an older patent application, but I think itâ€™s still important to see diffractive optics are not dead within



I don't see how this proves diffractive optics are or are not dead.


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## branden (May 25, 2011)

As a fan of the current 28mm, I'm very curious to see if this makes it to market


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