# Patent: More Diffractive Optics Supertelephoto Formulas



## Canon Rumors Guy (May 3, 2018)

```
<a href="https://www.canonnews.com/canon-patent-application-for-some-do-telephotos">Canon News</a> has uncovered another diffractive optic patent for supertelephoto optical formulas has shown up at the USPTO.</p>
<p>This patent covers the following:</p>
<ul>
<li>EF 200mm f/2</li>
<li>EF 400mm f/2.8</li>
<li>EF 800mm f/5.6</li>
</ul>
<p>Canon continues to work away at more and more diffractive optics development, but we’re still waiting to see new products come to market. The last DO lens released by Canon was back in 2014 when they announced the EF 400mm f/4 DO IS II.</p>
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```


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## NancyP (May 3, 2018)

Hope springs eternal...


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## kiwiengr (May 3, 2018)

Are these continued rumours of of various EF lenses a ruse by Canon to have the punters believe that FF mirrorless is not going elsewhere in terms of mount?


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## amorse (May 3, 2018)

kiwiengr said:


> Are these continued rumours of of various EF lenses a ruse by Canon to have the punters believe that FF mirrorless is not going elsewhere in terms of mount?


Do we know for sure that these are EF lenses (honest question)? The article here and on Canon news don't mention EF specifically so unless the patent itself says they are EF mount lenses, I'm not sure it's indicative of mirrorless applications either way. I am not familiar enough with the patent application process to verify in the patent itself to be fair.


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## jolyonralph (May 3, 2018)

I fully expect long lenses, indeed the majority of L lenses, to be EF mount for the foreseeable future. With a sensible adaptor this won't be an issue on the new body.


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## zim (May 3, 2018)

At the price those bad boys are going to be I'd expect a change mount service or be able to get different flavours unless a change of mount requires a different optical formula for optimal performance?

I'm imagining a salesperson trying to explain why a top of the range Canon FF lens and a top of the range Canon FF camera requires an adapter to fit together ???


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## Busted Knuckles (May 3, 2018)

GAS flare up just thinking of them. Hope I win the lottery soon.


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## kiwiengr (May 3, 2018)

amorse said:


> kiwiengr said:
> 
> 
> > Are these continued rumours of of various EF lenses a ruse by Canon to have the punters believe that FF mirrorless is not going elsewhere in terms of mount?
> ...



_This patent covers the following:

EF 200mm f/2
EF 400mm f/2.8
EF 800mm f/5.6_


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## Bennymiata (May 4, 2018)

It could be that Canon is developing diffractive optic lenses to make these long lenses more suitable for a new mirrorless system.
Mirrorless lenses SHOULD be smaller than dslr lenses. Isn't that correct?


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## hendrik-sg (May 4, 2018)

Bennymiata said:


> It could be that Canon is developing diffractive optic lenses to make these long lenses more suitable for a new mirrorless system.
> Mirrorless lenses SHOULD be smaller than dslr lenses. Isn't that correct?



No this is not fully correct, only for wide angel lenses. compare a 24-70 2.8 zooms, for FE mount and EF mount. the FE mount lens has a Prolongation to fill the shorter flange distance. So, the body is 2cm shorther, but almost all lenses will be 2cm longer.

The main advantage of a FF mirrorless system may be the following
- lower production costsn without mechanical parts
- higher selling price because it's innovative
- the need for new lenses, at least for people who dont want to use adapters.
- smaller wide angel lenses (if one buys them new)
- better Video/Life view AF

This advantages are mostly on the side of the sellers, so i dont understand the hype of the users.


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## kiwiengr (May 4, 2018)

hendrik-sg said:


> Bennymiata said:
> 
> 
> > It could be that Canon is developing diffractive optic lenses to make these long lenses more suitable for a new mirrorless system.
> ...



Agree completely. The advantage of mirrorless is not reducing flange to sensor distance, it's about getting rid of the mirror. I still want a viewfinder, I don't care if 50 grams has been taken off the body weight when I am using the 300 f2.8.


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## amorse (May 4, 2018)

kiwiengr said:


> amorse said:
> 
> 
> > kiwiengr said:
> ...



Ah yes, there it is - clearly I need to read more closely.

Thanks


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## Maximilian (May 4, 2018)

kiwiengr said:


> amorse said:
> 
> 
> > kiwiengr said:
> ...


Hi amorse! 

I' am trying to deliver a more specific and scientific answer to your question, if those formulae are EF or other lens types.

Short answer:
You'll have to look into the patents in detail so see the values of the optical formulae.
The people at Canon Rumors, Canon News, Northlight, etc. normally do that before they post an article or rumor. 
So normally you can believe them, if they write EF or EF-whatever mount.

Long answer:
To get the answer it is necessary to understand the patent and look at the calculated optical formulae in detail:
First you can find there the value of the "*image height*" which is half the radius of the image circle on the image plane. 
Here for all 5 examples this is 21.6 mm, which is typical for a FF sensor. So none of the calculated formulae is just for APS-C sensors like EF-S and EF-M mount.
The second interesting value is the "*back focus BF*". This is the distance between the last optical element and the image plane. For a normal EF mount/FF this must be more than about 44 mm. Otherwise the optical elements would protrude over the lens mount into the mirror box and therefore the mirror would collide with the lens. For EF-S or EF-M this can be shorter, but I don't have memorised the values.
For all these 5 examples (tele lenses) the BF is somewhere between 54.0 and 77.6 mm, so longer than 44 mm.
This also indicates that these are EF/FF lenses. 
If there was a new EF x mirrorless mount for FF sensors, these optical formulae would also work for that mount but the lens barrel would be longer to compensate the shorter flange distance between camera mount and image plane /sensor.


Edit: Normally nowhere in the patent the lens type or lens mount is mentioned. The patent just covers the optical formula and other specific information like the use of special optical glass or DO elements.


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## amorse (May 4, 2018)

Maximilian said:


> Hi amorse!
> 
> I' am trying to deliver a more specific and scientific answer to your question, if those formulae are EF or other lens types.
> 
> ...



That was a very insightful answer! Thanks. I wasn't sure where to look/what I was looking for to determine a potential flange distance. Your back focus explanation makes a lot of sense. So it certainly does seem geared toward an EF lens mount provided that a large barrel isn't included on the back of the lens.


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## NancyP (May 4, 2018)

The users of supertelephoto lenses are action photographers - sports or wildlife. Zero viewfinder lag is highly important to them, so the DSLR is the expected camera for these lenses.


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## Maximilian (May 4, 2018)

amorse said:


> ...
> That was a very insightful answer! Thanks.


You're welcome! I had to learn such things, too. Although I thought I already have some insight into optical physics.

Yet another thing, people quite often get confused with:
When you read about the "*Total lens length*" then this does not mean the physical length of the lens barrel but the length of the optical formula from front element to image plane. 
To get the physical length you have to subtract the flange distance, eg. about 44 mm for EF/EF-S lenses.


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## Talys (May 5, 2018)

NancyP said:


> The users of supertelephoto lenses are action photographers - sports or wildlife. Zero viewfinder lag is highly important to them, so the DSLR is the expected camera for these lenses.



Not only the lag I. The viewfinder, but the blackout when your eye isn't in the VF, but as it approaches the eyepiece. 

It is there in all MILCs to save battery, and it is super annoying when shooting wildlife, as those are precious lost fractions of a second.


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## Busted Knuckles (May 6, 2018)

Sorry for the hijack, just addressing the mirror issue..... With an "N" of 1. I used a Sony a6500 (mirror less APC) re: viewfinder. I turned off the screen and turned on the EVF to longest "on time" and then would occasionally do the 1/2 press to keep it turned o i.e. no start up lag, etc. (30 mins if memory serves me)

Shot over 6 hours on 1 little battery, chimping on the screen certainly kills battery.
-0- black out at 11 fps (tiny stutter but was able to keep all the birds in center frame all the time)
When I shot my 1dx EVERYONE within 50 meters knew I fired off a burst. When I shot the Sony NO ONE knew, even the guy 1 meter away. Virtually silent.

SOOOOOO. if you are into wildlife, the silence is golden. (though my otter shots came from my 1dx and his curiosity which was different than I expected)

I have both a 5d3 and a 1dx. 16-35 f4, 24 art, 50 art, 70-200 II, 150 -600 tammy, 90 T/S. All EF mounts. Rented Sony a6500, 5d4, 5dsR. (re-entered photo w/ a t3i which daughter now shoots occasionally) All told, quick file counts (don't delete anything, space is cheap) have the total frames at just below 250k

Skipping the 5d4/1dx2 generation. Looking forward to the 5dsR II (if it comes outs and wouldn't be so cool if it was mirror less).

All of this is to express - go rent one. Experience it. Yea the adapter kluge affected autofocus (cool Sony has peaking) but but but but but it is clear with a tech advancing (most places) as it is EVF will outperform the mirror - can't turn up the gain on a mirror like an EVF.

My experience leads me to pine for a Canon "pro" level mirror less. Wouldn't it be cool if they advance the SOA of the EVF and stick on the 5dSr replacement AND the 1Dx3.


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