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Author Topic: Patent: Canon EF 2.8x Teleconverter  (Read 9516 times)

Maui5150

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #15 on: March 27, 2012, 09:54:36 AM »
so the 70 - 200 F/2.8L IS II becomes a 196 - 560?

While F/8 is not ideal, still might add in some use.  The TCs already slow the AF down as it is, so manual focus is not as much a big deal.

Not sure the price... Probably somewhere in the $600 - $800 range, but if it works with the 70-200 like the 2x does, I could see there being interest

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #15 on: March 27, 2012, 09:54:36 AM »

marekjoz

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #16 on: March 27, 2012, 10:05:02 AM »
I'd imagine this would be very popular for Police/Secret Service In that a 400mm 5.6 with a 2.8x convertor would give a FF equivalent of nearly 1800mm on a crop body - that's a good couple of miles of range, set to live view, hook up to mains power and a laptop - sorted

... and closed in a big anti-wind box.
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smirkypants

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #17 on: March 27, 2012, 10:13:08 AM »
If you take the DX crop area of a D800, you have an optically perfect 1.5 teleconverter at 16MP. The only downside is that it's slow to shoot. There is no reason why Canon couldn't just create something as good with a 1.6 crop at 18MP. Sensor technology is racing ahead. I would much rather have a camera with an optically perfect built-in 1.6 crop teleconverter and add a 1.4x with a loss of only 1 stop than try to deal with the downsides of this 2.8x beast of a thing with all of its CR and loss of light.

maxxevv

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #18 on: March 27, 2012, 10:18:41 AM »
Would be the perfect companion for the 200mm f/2.0 IS L though ...  ;D

3kramd5

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #19 on: March 27, 2012, 10:25:12 AM »
<p><strong>Canon’s patent</strong></p>
<li>When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus</li>

I read that as it, like the 2X, adds two stops. So a 2.8 lens -> 5.6, not 8.

Unless Canon have found make a teleconverter that opens the aperture wider, I don't see how the teleconverter could multiply the focal length by 2.8 without (relatively) closing the aperture by three stops.

Maybe they designed it in such a way that it magnifies the apparent aperture (kinda like how constant f zooms work).

Dunno, just speculating based on that single bullet point. What else would it mean?
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marekjoz

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #20 on: March 27, 2012, 10:36:16 AM »
<p><strong>Canon’s patent</strong></p>
<li>When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus</li>

I read that as it, like the 2X, adds two stops. So a 2.8 lens -> 5.6, not 8.

Unless Canon have found make a teleconverter that opens the aperture wider, I don't see how the teleconverter could multiply the focal length by 2.8 without (relatively) closing the aperture by three stops.

Maybe they designed it in such a way that it magnifies the apparent aperture (kinda like how constant f zooms work).

Dunno, just speculating based on that single bullet point. What else would it mean?

It may not affect any current lens which it is attached to, as simply increasing f number accordingly by 3 stops. Apperture number comes from dividing focal length by real hole size. If focal length increases I don't see a way to increase the attached lens apperture hole.
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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #21 on: March 27, 2012, 10:39:13 AM »
<p><strong>Canon’s patent</strong></p>
<li>When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus</li>

I read that as it, like the 2X, adds two stops. So a 2.8 lens -> 5.6, not 8.

you've read wrong: you loose 2 stops with the 1.4 converter, and tree stops with the 2.0 .
this means 4 stops with the 2.8

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #21 on: March 27, 2012, 10:39:13 AM »

marekjoz

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #22 on: March 27, 2012, 10:45:42 AM »
<p><strong>Canon’s patent</strong></p>
<li>When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus</li>

I read that as it, like the 2X, adds two stops. So a 2.8 lens -> 5.6, not 8.

you've read wrong: you loose 2 stops with the 1.4 converter, and tree stops with the 2.0 .
this means 4 stops with the 2.8

I'm sorry you're not right - you loose 1 stop with 1.4 and two stops with 2.0. Assume you have 400mm f4. It means a hole is 100mm wide (400/100). If you add 1.4 TC, you have 560mm. So it becomes 560/100 = f5.6 and  f4 -> f5.6 = 1 stop. Calculate it with TC 2.0 and TC2.8 accordingly and you will find it.
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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #23 on: March 27, 2012, 10:59:32 AM »
<p><strong>Canon’s patent</strong></p>
<li>When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus</li>

I read that as it, like the 2X, adds two stops. So a 2.8 lens -> 5.6, not 8.

you've read wrong: you loose 2 stops with the 1.4 converter, and tree stops with the 2.0 .
this means 4 stops with the 2.8

I'm sorry you're not right - you loose 1 stop with 1.4 and two stops with 2.0. Assume you have 400mm f4. It means a hole is 100mm wide (400/100). If you add 1.4 TC, you have 560mm. So it becomes 560/100 = f5.6 and  f4 -> f5.6 = 1 stop. Calculate it with TC 2.0 and TC2.8 accordingly and you will find it.

yeap, you're right.
sorry

gatano

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #24 on: March 27, 2012, 11:11:26 AM »
let's hope Canon will add (again and officially) F8 focus capability in the next bodies, maybe the next 7DII (or 70D) is aimed at birders and will have F8 focus capabilities + high pixel density,
let's hope also next FF model (the overly awaited high resolution one) will have some(more than one) F8 focus points to make the 2.8x extender an usable tool

btw I already can use AF on F5.6 sensitive points staking a kenko dgx 1.4x + 2X tele converters, so also canon must/should be able to make this possible on current and (at least) future bodies

remember that F8 starts to cause some mild diffraction at current aps-c pixel densities, so I'm really surprised canon is working on it

sphax

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #25 on: March 27, 2012, 11:24:11 AM »
<p><strong>Canon’s patent</strong></p>
<li>When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus</li>

I read that as it, like the 2X, adds two stops. So a 2.8 lens -> 5.6, not 8.

you've read wrong: you loose 2 stops with the 1.4 converter, and tree stops with the 2.0 .
this means 4 stops with the 2.8

I'm sorry you're not right - you loose 1 stop with 1.4 and two stops with 2.0. Assume you have 400mm f4. It means a hole is 100mm wide (400/100). If you add 1.4 TC, you have 560mm. So it becomes 560/100 = f5.6 and  f4 -> f5.6 = 1 stop. Calculate it with TC 2.0 and TC2.8 accordingly and you will find it.

yeap, you're right.
sorry

I love how you fight about "stops" dudes ... bit of a clue : take F/2,8 or F/4,0 or whatever indeed and just multiply by the number on the extender ... magic ;)

marekjoz

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #26 on: March 27, 2012, 11:29:26 AM »
<p><strong>Canon’s patent</strong></p>
<li>When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus</li>

I read that as it, like the 2X, adds two stops. So a 2.8 lens -> 5.6, not 8.

you've read wrong: you loose 2 stops with the 1.4 converter, and tree stops with the 2.0 .
this means 4 stops with the 2.8

I'm sorry you're not right - you loose 1 stop with 1.4 and two stops with 2.0. Assume you have 400mm f4. It means a hole is 100mm wide (400/100). If you add 1.4 TC, you have 560mm. So it becomes 560/100 = f5.6 and  f4 -> f5.6 = 1 stop. Calculate it with TC 2.0 and TC2.8 accordingly and you will find it.

yeap, you're right.
sorry

I love how you fight about "stops" dudes ... bit of a clue : take F/2,8 or F/4,0 or whatever indeed and just multiply by the number on the extender ... magic ;)

Wow, how did you do that? That's really a case for Penn & Teller
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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #27 on: March 27, 2012, 11:33:57 AM »
<p><strong>Canon’s patent</strong></p>
<li>When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus</li>

I read that as it, like the 2X, adds two stops. So a 2.8 lens -> 5.6, not 8.

you've read wrong: you loose 2 stops with the 1.4 converter, and tree stops with the 2.0 .
this means 4 stops with the 2.8

I'm sorry you're not right - you loose 1 stop with 1.4 and two stops with 2.0. Assume you have 400mm f4. It means a hole is 100mm wide (400/100). If you add 1.4 TC, you have 560mm. So it becomes 560/100 = f5.6 and  f4 -> f5.6 = 1 stop. Calculate it with TC 2.0 and TC2.8 accordingly and you will find it.

yeap, you're right.
sorry

I love how you fight about "stops" dudes ... bit of a clue : take F/2,8 or F/4,0 or whatever indeed and just multiply by the number on the extender ... magic ;)

Wow, how did you do that? That's really a case for Penn & Teller

apart from the relatively simple ratios, I was concerned by the loss due to the additional elements.
( a polarizing filter doesn't change the focal but causes 1 full stop loss for example)

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #27 on: March 27, 2012, 11:33:57 AM »

marekjoz

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #28 on: March 27, 2012, 11:37:52 AM »
<p><strong>Canon’s patent</strong></p>
<li>When doubled, twice the lateral aberration, longitudinal aberration is 4 times greater rate of expansion, because the F-number is also double, longitudinal aberration is twice per depth of focus</li>

I read that as it, like the 2X, adds two stops. So a 2.8 lens -> 5.6, not 8.

you've read wrong: you loose 2 stops with the 1.4 converter, and tree stops with the 2.0 .
this means 4 stops with the 2.8

I'm sorry you're not right - you loose 1 stop with 1.4 and two stops with 2.0. Assume you have 400mm f4. It means a hole is 100mm wide (400/100). If you add 1.4 TC, you have 560mm. So it becomes 560/100 = f5.6 and  f4 -> f5.6 = 1 stop. Calculate it with TC 2.0 and TC2.8 accordingly and you will find it.

yeap, you're right.
sorry

I love how you fight about "stops" dudes ... bit of a clue : take F/2,8 or F/4,0 or whatever indeed and just multiply by the number on the extender ... magic ;)

Wow, how did you do that? That's really a case for Penn & Teller

apart from the relatively simple ratios, I was concerned by the loss due to the additional elements.
( a polarizing filter doesn't change the focal but causes 1 full stop loss for example)

You are right - there is additional lost of light on elements inside TC.
And this can be another win over stacking 2.0 and 1.4 - for sure there will be less elements than sum of 1.4 and 2.0.
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dolina

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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #29 on: March 27, 2012, 11:47:14 AM »
With 2.8x applied

800mm f/5.6 = 2,240mm f/15.68
600mm f/4.0 = 1,680mm f/11.2
500mm f/4.0 = 1,400mm f/11.2
400mm f/2.8 = 1,120mm f/7.84
300mm f/2.8 = 840mm f/7.84
200mm f/2.0 = 560mm f/ 5.6
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Re: Patent: Canon EF 2.8x Teleconverter
« Reply #29 on: March 27, 2012, 11:47:14 AM »