# Patents: 24mm f/2.8, 50mm f/1.2, 300mm f/4



## Canon Rumors Guy (Jan 15, 2012)

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<strong>New Optical Formula Patents</strong>

A new patent showcasing 3 different focal lengths has come to light.</p>
<ul>
<li><strong>Patent Publication No. 2012-8352</strong>
<ul>
<li><span><span>2012.1.12 Release Date</span></span></li>
<li><span><span>Filing date 2010.6.25</span></span></li>
</ul>
</li>
<li><strong>Example 1</strong>
<ul>
<li><span><span>Focal length f = 294.0mm</span></span></li>
<li><span><span>Fno = 4.14</span></span></li>
<li><span><span>= 8.42deg angle.</span></span></li>
<li><span><span>15 sheets 11 groups configured</span></span></li>
<li><span><span>One element radial refractive index profile</span></span></li>
<li><span><span>Bowen ratio 0.78</span></span></li>
<li><span><span>Inner</span></span><span><span> Focus (the second lens group for focusing)</span></span></li>
</ul>
</li>
<li><strong>Example 3</strong>
<ul>
<li><span><span>Focal length f = 51.5mm</span></span></li>
<li><span><span>Fno = 1.25</span></span></li>
<li><span><span>= 45.6deg angle.</span></span></li>
<li><span><span>Configuration 6 each group 10</span></span></li>
<li><span><span>Two elements radial refractive index profile</span></span></li>
<li><span><span>One aspherical surface 1</span></span></li>
</ul>
</li>
<li><strong>Example 4</strong>
<ul>
<li><span><span>Focal length f = 24.7mm</span></span></li>
<li><span><span>Fno = 2.86</span></span></li>
<li><span><span>= 82.4deg angle.</span></span></li>
<li><span><span>Configure each group 11 10</span></span></li>
<li><span><span>One element radial refractive index profile</span></span></li>
<li><span><span>Rear focus (the third lens group and the second lens for focusing)</span></span></li>
</ul>
</li>
<li><strong>The principle cause chromatic aberration</strong>
<ul>
<li><span><span>Light is refracted at the interface of the lens</span></span></li>
<li><span><span>Within the lens are not refracted rays</span></span></li>
<li><span><span>The refractive index is different for each wavelength</span></span></li>
</ul>
</li>
<li><strong>Element and the axial refractive-index distribution is</strong>
<ul>
<li><span><span>Refractive index change in the direction of optical axis</span></span></li>
<li><span><span>This patented technology is not used (as introduced)</span></span></li>
</ul>
</li>
<li><strong>Element and the radial refractive index profile is</strong>
<ul>
<li><span><span>Refractive index change in a direction perpendicular to the optical axis</span></span></li>
<li><span><span>Rays are refracted at the boundary and both the lens in the lens (chromatic aberration occurs).</span></span></li>
<li><span><span>Chromatic aberration can be corrected if appropriate refractive index profile</span></span></li>
<li><span><span>Rather than spherical or aspherical, planar (flat glass), but I (easy processing)</span></span></li>
</ul>
</li>
<li><strong>Canon’s patented</strong>
<ul>
<li><span><span>Elements to create a radial refractive index profile optimized for each wavelength the refractive index profile is difficult</span></span></li>
<li><span><span>Patented technology, the characteristics of chromatic dispersion (Abbe number, a partial dispersion ratio) to optimize, to compensate for chromatic aberration</span></span></li>
<li><span><span>Optimize the calculation, line d, line C, line F, to compensate for chromatic aberration of four wavelengths simultaneously in the g-line</span></span></li>
<li><span><span>Create a radial refractive index profile element as a mixture of resin</span></span></li>
</ul>
</li>
</ul>
<p><strong> Source: [<a href="http://egami.blog.so-net.ne.jp/2012-01-16">EG</a>]</strong></p>
<p><strong><span style="color: #ff0000;">c</span>r</strong></p>
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## Caps18 (Jan 16, 2012)

dilbert said:


> Wow, a follow up to the 50/1.2L so soon?



Are they updating it or just protecting the current model from outside competition?


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## preppyak (Jan 16, 2012)

Could also be related to their cinema lenses at some level.


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## Mt Spokane Photography (Jan 16, 2012)

We are seeing mention of that radial refractive index resin lens (plastic) again. I think that we will see this in upgraded primes, it appears to be able to make improvements possible without increasing the size. Only the cost will get significantly larger.


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## willrobb (Jan 16, 2012)

dilbert said:


> Wow, a follow up to the 50/1.2L so soon?



I'm guessing the time between filing a patent and seeing the lens in the shops could be several years. Wonder what they would do to make the 50L better anyway? A tad wider to allow 77mm filters would save people buying new ones for the current 72mm 50L, but in terms of build and IQ I for one am very happy....maybe says something about my standards :


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## vlim (Jan 16, 2012)

> patent 300mm F/4
> 
> Focal length f = 294.0mm
> Fno = 4.14
> ...



Does it mean a new 300mm F/4 is coming for 2012 ? This is not the first patent we have seen for this lens... I hope for it


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## dshipley (Jan 16, 2012)

willrobb said:


> I'm guessing the time between filing a patent and seeing the lens in the shops could be several years. Wonder what they would do to make the 50L better anyway? A tad wider to allow 77mm filters would save people buying new ones for the current 72mm 50L, but in terms of build and IQ I for one am very happy....maybe says something about my standards :



There are many many people who have had issues with focus on the 50 f/1.2 L... mainly focus shifting.


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## jasonsim (Jan 17, 2012)

I am one that suffered with the 50mm 1.2L's focusing issues. It would be dialed in with MFA for closer focusing distances, but then it would be way off for longer focus distances closer to infinity. Also it would most of the time not lock focus on the subject. I would have to focus on something else and then re focus on my subject to get good results. Not sure if this is the "focus shift" folks talk about. 

If my copy did not have the above mentioned issues, I would have kept it. It produced lovely results at f1.8 and f2. Mine was kinda soft at 1.2 and also suffered a bit of chromatic aberration. 

No that I've moved to Full Frame and have a 35mm 1.4L and 85mm 1.2L II, I'm not sure that a 50mm is necessary.


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## tysonboh (Jan 22, 2012)

does this mean a new canon ef 24mm 2.8 will be coming out? and when do you expect it to be released? as im currently looking at buying this lens for my 600d.


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## dolina (Jan 22, 2012)

I look forward to an improved 50/1.2


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## Ellen Schmidtee (Jan 22, 2012)

tysonboh said:


> does this mean a new canon ef 24mm 2.8 will be coming out? and when do you expect it to be released? as im currently looking at buying this lens for my 600d.



It means a new EF 24mm f/2.8 *might* come out. As most patents don't turn into lenses, Canon didn't release any non-L primes for at least a decade, and if it did turn into a lens, it would take a while to announce + produce + reach the shops.

If you want an EF 24mm f/2.8, I think it would be best to buy the available model.


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