Patent: Canon EF 2.0X TC With Diffractive Optics Element

[Canon Rumors]

<p><a href="http://www.canonrumors.com/wp-content/uploads/2014/10/dotc.png"><img class="aligncenter wp-image-17614 size-full" src="http://www.canonrumors.com/wp-content/uploads/2014/10/dotc.png" alt="dotc" width="181" height="111" /></a></p>
<p>A patent showing a 2x teleconverter with a diffractive optic element (DO) has surfaced. The 2.0x teleconverter could use a little length reduction, though I’m not sure if DO would reduce the size of the current TC all that much.</p>
<p><strong>Patent Publication No. 2014-145870 (Google Translated)</strong></p>
<ul>
<li>Published Date 2014.8.14</li>
<li>Filing date 2013.1.29</li>
</ul>
<p><!--more--></p>
<p><strong>Example 1</strong></p>
<ul>
<li>Focal length -109.09mm</li>
<li>Magnification 2.00x</li>
<li>4 group 9-lens configuration</li>
<li>One plane diffraction plane (the first group)</li>
<li>Master lens</li>
<li>Focal length f = 293.76mm</li>
<li>Fno. 2.91</li>
<li>Half angle ω = 4.21 °</li>
<li>Image height Y = 21.64mm</li>
<li>The overall length of the lens 275.41mm</li>
<li>BF 53.79mm</li>
<li>15 sheets 11 groups lens configuration</li>
<li>Protective glass 1</li>
<li>Rear filter 1</li>
<li>UD 2</li>
<li>Fluorite 1</li>
</ul>
<p><strong>Canon Patents</strong></p>
<ul>
<li>I and the diffraction plane cemented surface of the cemented lens closest to the object side</li>
<li>This arrangement can suppress the flare</li>
</ul>
<p>Source: [<a href="http://translate.google.com/translate?sl=auto&tl=en&u=http://egami.blog.so-net.ne.jp/2014-10-19" target="_blank">EG</a>]</p>
<p><strong><span style="color: #ff0000;">c</span>r</strong></p>

 

[jrista]

Maybe the patent isn't for size/length/weight reduction, but rather IQ improvement. Diffractive optics are better at managing light dispersal. That can allow for a shorter lens, but that isn't necessarily the sole purpose. I for one would like to see better IQ out of a 2x TC...the current TC III is good, but it does impact IQ.

 

[AprilForever]

Maybe the patent isn't for size/length/weight reduction, but rather IQ improvement. Diffractive optics are better at managing light dispersal. That can allow for a shorter lens, but that isn't necessarily the sole purpose. I for one would like to see better IQ out of a 2x TC...the current TC III is good, but it does impact IQ.

That's what I was thinking too when I saw it. It would be indeed fascinating if they can improve it!

 

[dufflover]

True that does make sense. Given how it's magnifying that smaller section of the frame into a 35mm sensor area over that relatively short distance a DO design would help.
Then again in most cases the lens it gets bolted onto seems to be bigger the bottleneck anyway.

 

[Mt Spokane Photography]

A diffractive element lets you bend light rays more without some of the side effects like chromatic aberrations. The additional bending allows for a shorter lens.

DO elements are very expensive, so, unless you wanted a shorter TC, the additional elements used in a regular TC cost less and work very well.

I could see a very desirable but expensive application for a TC with a DO element in a lens that has a built-in TC that can be engaged / disengaged.

 

[Jim Saunders]

I could see a very desirable but expensive application for a TC with a DO element in a lens that has a built-in TC that can be engaged / disengaged.

The logical conclusion there is more big whites with integral TCs; a 70-200 f/2.8 with an integral 1.4x would be handy for smaller-court sports.

Jim

 

[NancyP]

That's what long lens feet on Arca-Swiss dovetail QR system are for - slide the foot back and forth in the clamp to balance with and without teleconverter.

 

[Loswr]

Umm, at the risk of stating the obvious, we all know that TC's increase the deflection of the camera body, right ?!
Never seen a TC with a tripod/monopole mounting !

Is that a problem? I suppose it could be if you are attaching your lens' tripod foot to the support (tripod/monopod) directly, but I suspect the vast majority use a quick release (e.g. Arca Swiss type) lens plate or replacement foot, when can be positioned at varying locations within the clamp jaws for appropriate balance (±TC, ±flash, etc.).

 

[davidcl0nel]

DO elements are very expensive, so, unless you wanted a shorter TC, the additional elements used in a regular TC cost less and work very well.

But if it brings more quality, why not?
I know, the TC are often used in the "small" budget range too, but maybe this is for the high-end-lenses only?
If you have a 400/2.8 and get it with such a TC to a equal or better result than the 800/5.6 (dont forget the weight), why not? And if you pay 10k für the 400/2.8 a TC for 1500$ is still the better choice than a 13k 800/5.6. ;-) And more versatile.

 

[Mt Spokane Photography]

Hi, thanks for that feedback @>neuroanatomist and @>NancyP. Cheerz !

It has been my experience, that most people purchase a medium-range fast-aperture lens, and then down the road a bit, they add a TC to the kit/gear bag.
But to find yourself suddenly nursing a 600mm f/4 with a TC on a thin-walled-camera-body. I see a chance of heart-break.

I am a DIY Loony, I make all my lens' (including make my own 'glass')
I have a Pentax P50 here with the front of the camera pulled out so far, a good 1/2 inch(12mm)
Arca Swiss seem to have a very accommodating level of flexibility. No doubt there are others also.



propter artem artium

Adding a TC to a big white puts very little added stress on a camera body. Doesn't matter if its a eos-M or a 1 series.

The lens is the heavy part, and its mounted to the tripod.

 

[Loswr]

It has been my experience, that most people purchase a medium-range fast-aperture lens, and then down the road a bit, they add a TC to the kit/gear bag.
But to find yourself suddenly nursing a 600mm f/4 with a TC on a thin-walled-camera-body. I see a chance of heart-break.

I don't understand your point. I've used a 70-200/2.8 and a 600/4 with TCs, on and off tripods. The lens mount on all bodies is quite strong.