# Patent: Canon 3.6-255mm F2.8-7 w/ Built-in Extender for PowerShot



## Canon Rumors Guy (Dec 25, 2016)

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An interesting lens patent for a PowerShot camera has appeared, in the form of a Canon 3.6-255mm F2.8-7 lens with a built-in extender that can make the lens 2000mm f/10 when converted to 35mm.</p>
<p>Patent publication number 2016-212210 (Google translated)</p>
<ul>
<li>Release date 2016.12.15</li>
<li>Application date 2015.5.7</li>
<li>Zoom ratio 66.07</li>
<li>Focal length 3.71 10.16 245.00</li>
<li>F number 2.90 4.99 7.07</li>
<li>Half angle of view (degree) 40.59 20.88 0.91</li>
<li>Lens total length 94.31 86.88 150.26</li>
<li>BF 9.45 16.24 9.56</li>
</ul>
<p>Super telephoto (D)</p>
<ul>
<li>Focal length 359.99</li>
<li>F number 10.39</li>
<li>Half angle of view (degree) 0.62</li>
<li>Lens total length 150.26</li>
<li>BF 3.56</li>
</ul>
<p>With the PowerShot SX70 HS around the corner and recent patents showing 100x zoom optical formulas, this is likely part of that development process.</p>
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## Don Haines (Dec 25, 2016)

Of all the superzooms that I have seen, unfortunately Canon seems to have the worst. Hopefully this is part of a plan to leapfrog the competition.


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## hendrik-sg (Dec 25, 2016)

3.6 - 255mm f 2.8-7.0

equals to (if the crop factor is 5.6)

20-1430mm f 15.7-55

This is far beyond the diffraction limit. Magnifying some amount beyond the diffraction limit may may give some benefit, because the resolving pover somehow converges, the losses are multiplied, and with some "oversampling" the loss of missing sensor resolution dismishes. Exactly at the diffraction limit, the losses caused by diffraction and by lack of sensor resolution are equal.

This amout is a complete overkill, it's just physical nonsense, and adding a converter to such a lens can not give any additional information, it's not there.

This is almost unhonest, sell people a camera which gives a magnification that is so high, that the image is getting blured by physical reasons. This is another way to kill the PS market, people are excioted by the promise given and the following disapointment is not evitable.

This customer will rely on the good old phone, if a real (and big) camera gives only blured pics.


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## pokerz (Dec 26, 2016)

Please add BSI sensor and PDAF to it.


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## Speedsurfer142 (Dec 26, 2016)

pokerz said:


> Please add BSI sensor and PDAF to it.



Althow you are saying something else, I would live to see a BSI (Bull Shit Indicator) on the lens next to the fake zoomrange and fake f-stop indicator.


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## hubie (Dec 26, 2016)

hendrik-sg said:


> 3.6 - 255mm f 2.8-7.0
> 
> equals to (if the crop factor is 5.6)
> 
> ...



I guess you got something wrong there. The aperture of the lens remains the same no matter what crop factor you use. The crop factor is nothing more than a comparison of the sensor size to the full frame (and some people deduce other picture properties from it).

The physical dimensions of the lens are independant of it... although I doubt the lens will create an image area anywhere near a full frame sensor.


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## JMZawodny (Dec 26, 2016)

Some consumers buy the specs and don't have the discerning eye to tell good from bad. This will sell well enough, should it ever come to market, to make money.


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## MrToes (Dec 27, 2016)

I bought one of the older Canon super zooms (50 HS) and it works ok. Can't wait to see a super zoom with a nice 24MP or so sensor with modern technology! Would be worth the upgrade!


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## neonlight (Jan 1, 2017)

If I recall correctly the diffraction limit is set by the diameter of the lens. SO if the base lens is 255mm f/7 the diameter is 36 mm and in the central optical path (555nm?) this makes the angular resolution 1 milli-degree. Compared to the telephoto angle of 0.9 degrees that is about 1 part in 1/1000 or several pixels, so the lens won't match the big whites any time soon.


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## rs (Jan 1, 2017)

hubie said:


> hendrik-sg said:
> 
> 
> > 3.6 - 255mm f 2.8-7.0
> ...



Yes, the physical aperture remains the same, no matter what extender or equivalence you are referring to. But if the focal length changes as a result of extenders or how its referred to with equivalence, the aperture ratio _has_ to change in those terms. After all, 255/7.0 (focal length/aperture ratio at full zoom) reveals it has a physical aperture or entrance pupil of 36.4mm at full zoom.

If you take the crop factor to be 5.6, it cannot be equivalent to a 1428/7.0 lens, as that requires an entrance pupil of 204mm. Whereas a lens which is equivalent of 1428/39.2 (both multiplied by 5.6) does indeed have the same 36.4mm entrance pupil.


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