Patent: EF-M 55-300mm f/4.5-5.6 DO IS

[Canon Rumors]

Canon continues to develop diffractive optics technology, and this time it’s for the EF-M mount. A patent for an EF-M 55-300mm f/4.5-5.6 DO IS optical formula has appeared. The lens is for APS-C mirrorless cameras.</p>
<p>Patent Publication No. 2015-232674 (Google Translated)</p>
<ul>
<li>Published 2015.12.24</li>
<li>Filing date 2014.6.11</li>
<li>Zoom ratio 5.27</li>
<li>Focal length 55.04 135.00 290.01</li>
<li>F-number 4.60 5.18 6.30</li>
<li>Angle of view 13.94 5.78 2.70</li>
<li>Image height 13.66 13.66 13.66</li>
<li>Overall length of the lens 136.00 175.46 192.00</li>
<li>BF 35.50 35.50 35.50</li>
</ul>
<p>I’m not sure how likely a DO lens is for the EOS M system, unless they’ve figured out a way to bring costs down.</p>
<span id="pty_trigger"></span>

 

[Maximilian]

• Overall length of the lens 136.00 175.46 192.00
• BF 35.50 35.50 35.50

I’m not sure how likely a DO lens is for the EOS M system, unless they’ve figured out a way to bring costs down.

About 100 mm length (contracted) for an up to 300mm lens sounds attractive for the EOS M system.
But for sure the price will be the killer argument if this will become a product.
Same MRSP as the EF 70-300mm f4.0-5.6 IS USM should be the goal.

 

[jma5terj]

<ul>
<li>F-number 4.60 5.18 6.30</li>
</ul>

Looks like f/4.5-6.3.

 

[kenny]

Only the mount is guaranteed, not the camera its attached to. Pro mirrorless anyone?

 

[docsmith]

Glad to see that they are making progress with more M lenses. Also, this fits with my take on the "M" system in that its most distinct advantage is its small size. So, use DO and make a small telephoto lens. Nice.

That said, this M1 owner is 90% to the point of selling his M gear off in favor of something truly pocketable such as the G7X or R100 (III or IV).

When I want more, I take my 5DIII kit. The most value I can see out of the M system for me would be an uber small travel kit or light weight for hiking when I want something other than 24-100 or 24-70 mm. Thus far, I would have been better off with a pocketable camera. Add more lenses and maybe the "M" system could be worth it.

But, what I would really want to see is shorten the current 70-300 L by a few inches by introducing this technology into a 70-300 f/4-5.6 L DO IS USM. That could be an epic travel lens.

 

[Foxdude]

Only the mount is guaranteed, not the camera its attached to. Pro mirrorless anyone?

Yes please! I'm glad to see these Ef-m lens patents. Really like to see pro mirrorless system from Canon, with some high quality native lenses.

 

[Loswr]

When I want more, I take my 5DIII kit. The most value I can see out of the M system for me would be an uber small travel kit or light weight for hiking when I want something other than 24-100 or 24-70 mm. Thus far, I would have been better off with a pocketable camera.

That's the value of the M system to me – a small/light kit that is neverless an actual kit, with a variety of options for framing, DoF, and lighting. My entire M kit (M2, 11-22, 22/2, 18-55, 270EX) takes up about the same volume as my 1D X plus 24-70/2.8 II and weighs only slightly more than just the L lens.

When walking around Paris with my family (wife + three young kids), the M was definitely a benefit and would not have been replaceable with a pocketable camera like a G7X or RX100. One of the main reasons for that is the availability of an ultrawide lens - I'm not aware of any P&S that offer a native ultrawide FoV, and while there are converter options that reduces the size advantage and hits IQ pretty hard.

EOS M at 11mm in the Louvre:

 

[sunnyVan]

When I want more, I take my 5DIII kit. The most value I can see out of the M system for me would be an uber small travel kit or light weight for hiking when I want something other than 24-100 or 24-70 mm. Thus far, I would have been better off with a pocketable camera.

That's the value of the M system to me – a small/light kit that is neverless an actual kit, with a variety of options for framing, DoF, and lighting. My entire M kit (M2, 11-22, 22/2, 18-55, 270EX) takes up about the same volume as my 1D X plus 24-70/2.8 II and weighs only slightly more than just the L lens.

When walking around Paris with my family (wife + three young kids), the M was definitely a benefit and would not have been replaceable with a pocketable camera like a G7X or RX100. One of the main reasons for that is the availability of an ultrawide lens - I'm not aware of any P&S that offer a native ultrawide FoV, and while there are converter options that reduces the size advantage and hits IQ pretty hard.

EOS M at 11mm in the Louvre:

Feel exactly the same way. Even though there aren't many M lenses yet, the ones in existence are pretty decent. Ultrawide is an important part of any kit. And that's why i IR converted my M instead of a p&s.

I've looked into G5x, g7x, etc. I'm not convinced that a 1in sensor can provide good enough quality for printing. I can shoot iso 1600 with m3 if i must. I don't think any of these smaller sensor cameras would give me that flexibility.

 

[brad-man]

Seems a bit far fetched to believe that this lens will be produced any time soon, but it's nice to know Canon is thinking about it. In the meantime, I'd like some fast primes please...

 

[AvTvM]

all fine and well. But a dark and expensive tele-zoom is certainly no priority for the Canon EOS M system.
There is only one priority: a high(er) end body, as small as possible and fully competitive on all counts from sensor to AF system to conncetivity ... and the bar for "fully competitive is moving upwards" ... Sony "A6100" might really be just around the corner now.

@Neuro: like your Louvre shot, especially "the overwhelming sense of scale" it conveys.

Was also there during new Year and also had my EOS M(1) plus lenses along. Used all of them, even the 55-200. Did however not encounter a situation for which I'd have needed or wanted 300mm native FL.

Skipped the Louvre this time, went to see newly renovated Musee Orsay again. Quite a place. Some images with each of the EF-M lenses here -> http://www.canonrumors.com/forum/index.php?topic=28796.0

 

[AvTvM]

What physical size and weight do you think this lens would be?

EF-M 55-200: ØxL: 60.9x86.5mm, 260g, 52mm filter thread

55-300 patent: minimal length is already 136mm?, diameter? Weight?

Not sure, how many would be willing to pay 2 or 3 times more for a much larger and equally dark f/6.3 crop lens that offers just 100mm more FL? Especially since majority of current EOS M owners and potential buyers of a Pro M body also have EF (tele) glass already ...

Personally I would only need 300mm (or more) on my M system, when hiking/mounataineering - to capture occasional alpine ibex or mountain goats or deer ... in sunrise or sunset on that far ridge or marmots playing on an alpine meadow or birds of prey ... but on a purely opportunistic basis. If i were really into wildlife i'd take along a serious tele with more FL ... 100-400 II would be the lightest and most compact option. But the i might as well take a 7D Ii along ... not an EOS M.

 

[Loswr]

55-300 patent: minimal length is already 136mm?, diameter? Weight?

Length a bit shorter, 118-120mm. The length in a patent is for the optical formula, it's measured starting at the sensor.

 

[bainsybike]

55-300 patent: minimal length is already 136mm?, diameter? Weight?

Length a bit shorter, 118-120mm. The length in a patent is for the optical formula, it's measured starting at the sensor.

That would make it about the same length as the EF-S 55-250 STM. I'd have thought they could do that without using DO.

@Neuro: like your Louvre shot, especially "the overwhelming sense of scale" it conveys.

+1

 

[Loswr]

Some raw math figures, accounting for 1.6 crop shrink on angle of incidence and reduction of EF-M mount length + slower F-stop on long end...

DxL = 2.1x3.6" (but they'll make it a 2.4x3.6 since 2.4 diameter seems to be the EF-M standard, thus some dead space which is fine)

So you believe the lens will retract for storage (like the 11-22) by >1"?

 

[Loswr]

Some raw math figures, accounting for 1.6 crop shrink on angle of incidence and reduction of EF-M mount length + slower F-stop on long end...

DxL = 2.1x3.6" (but they'll make it a 2.4x3.6 since 2.4 diameter seems to be the EF-M standard, thus some dead space which is fine)

So you believe the lens will retract for storage (like the 11-22) by >1"?

Not necessary. DO shortens the light path making long focal optics shorter in length; DO is great in telescopes, or telephoto. The aperture is less forgiving, hence them slowing the long end to keep the frontal aperture slower to keep the diameter down. Wider focals make good collapsing candidates, and terrible DO candidates.

Then how do you reconcile your estimated length of 3.6" with the patented DO optical formula with a minimum total lens length of 136mm?

 

[AvTvM]

... Could be true as the optical performance characteristics of the latest powershots, Canon has been using DO zooms in their G1X II and G7X-G5x, hence how they can squeeze more focal then Sony into the same form factor. I say this as the spherical aberration wide open on the G1X II and G7X is bad, you gotta stop down when shooting wide.

Sorry, but didn't you write a few posts earlier, that DO lenses perferom best NOT wide open and IQ does not really improve by stopping down? I have not seen any mentioning before of DO-lens design in G1X II and G7X.

Personally I only like Fresnel lenses in old Light Houses, but not in my camera lenses. Have not bought one, will not. To me it means applying an "unnatural trick" to the incoming photons, "forcing them to bend around too narrow corners" ... I expect those photons to not like that treatment and it is bound to have all sorts of nasty side effects ... with the potential to bite me in the back when I need it least and/or am not prepared for it to happen ...

 

[StudentOfLight]

Given f/6.3 ... and working diffraction limit backwards ... would this mean that the most that this APS-C lens could deliver would be 30MP ???

Is this Canon's view of the limit of the EF-M system, at least in terms of the consumer segment?

 

[Loswr]

Some raw math figures, accounting for 1.6 crop shrink on angle of incidence and reduction of EF-M mount length + slower F-stop on long end...

DxL = 2.1x3.6" (but they'll make it a 2.4x3.6 since 2.4 diameter seems to be the EF-M standard, thus some dead space which is fine)

So you believe the lens will retract for storage (like the 11-22) by >1"?

Not necessary. DO shortens the light path making long focal optics shorter in length; DO is great in telescopes, or telephoto. The aperture is less forgiving, hence them slowing the long end to keep the frontal aperture slower to keep the diameter down. Wider focals make good collapsing candidates, and terrible DO candidates.

Then how do you reconcile your estimated length of 3.6" with the patented DO optical formula with a minimum total lens length of 136mm?

See the EF 70-300mm DO IS Specs... 3.93" in length... Mind you that's on an EF mount. So 1. You're loosing roughly .2" on the mount, as the EF-M mount sits closer to the camera, and 2. The crop conversion shaves off a hair on the angle of incidence necessary to maintain 300mm on an APS-C, (not much though) so I threw in .1" for that making 3.6. Technically it could be shorter... Canon's been using high grade aluminum construction in the EF-M lenses, so the length could be a hair shorter even, possibly also closer to 400g in weight as well.

Oh, I see. You're formulating a guess on an idea of what an EF-M'd version of the 70-300 DO might look like if it was a 55-300mm lens. I'm just counting on Canon to be able to properly report the measurement of a lens in a patent for it.

 

[AvTvM]

Based on the patent, the EF-M 55-300 @55mm FL should be 136mm optical length to sensor plane minus flange distance [BF = 35.6mm] - not counting any parts protruding the front lens (e.g. filter thread) - so we're looking at min. 100mm / about 4" ... correct? Which is right where the EF 70-300 DO IS USM is ... 82.4D x 99.9mm L and 58mm filter thread.

Maybe a "collapsible design" for a shortened "parking position" (like on 11-22) ... Canon has not used one yet .. but Nikon does ... on their AF-S DX Nikkor 55-200mm f/4-5.6G ED VR II introduced in 2015. It is a bit shorter but fatter D 70.5 x 83mm L, 52mm filter thread - compared to current EF-M 55-200. And a bit faster [f/5.6].

 

[Loswr]

Based on the patent, the EF-M 55-300 @55mm FL should be 136mm optical length to sensor plane minus flange distance [BF = 35.6mm] - not counting any parts protruding the front lens (e.g. filter thread) - so we're looking at min. 100mm / about 4" ... correct? Which is right where the EF 70-300 DO IS USM is ... 82.4D x 99.9mm L and 58mm filter thread.

You're interpreting the numbers incorrectly. The patent specifies a shortest overall lens length of 136mm, which is the distance from the sensor to the front surface of the front element. The flange focal distance (sensor to mount surface) for the M series is 18mm, that's the number you subtract from the minimum overall length to determine the approximate length of the lens (it's going to be slightly longer than the optical formula because the filter threads extend a bit beyond the front element).

The backfocus distance is generally from the rear element to the sensor (sometimes from an internal negative element, depending on the design), and the rear element is usually recessed a bit within the lens relative to the mount, particularly in telephoto and telezoom lenses. In some cases like the 85/1.2L, some ultrawide lenses, and some EF-S lenses, the rear element extends slightly into the mirror box so the backfocus distance is less than the flange focal distance.

136mm – 18mm = 118mm = 4.65", which was why I indicated that thetechhimself's suggestion of a 3.6" lens was slightly over an inch too short, and initially wondered if he was suggesting a collapsing design like the M11-22.

Certainly Canon might release a lens shorter than 118mm, but it wouldn't be the lens described in this patent.