Canon Attempts New Supertele Patents

Dragon

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May 29, 2019
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What makes you think so? They all have a secondary mirror right behind the front element.

View attachment 202886
The secondary mirror is typically glued to the back of the front element. In this case, the front element appears flat and the diagram shows the light rays coming straight in to a mirror of the same diameter. I did not mean that the lens would not have doughnut bokeh, but rather that the front element would not be ground lens of doughnut shape, which is typical of most cats (and the mirror is typically smaller than the front element).
 

entoman

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I think these new cats are about size and price. Note that the design appears to have flat glass at the front and not a doughnut lens, so the only large optic in the whole thing is the mirror and it appears that is spherical, so not hard to grind.
My suspicion is that these cats, if they actually get into production (which I doubt), would be rather more expensive than you think.
I don't think they'd be "budget" lenses in the same price band as e.g. the 600/11, 800/11 and 100-400/5.6-8, in fact it wouldn't surprise me if they were "L" standard weather-sealed lenses, with a hefty price tag to match.

I would envisage the primary target buyers as media agencies and paparazzi types, needing highly portable get powerful lenses to capture politicians, "celebrities" etc from a safe distance.

I may have misunderstood your final sentence, but having "donut" bokeh is inherent in the design. The reflector behind the middle of the front element will automatically produce a "hole" in the bokeh.

Having used mirror lenses in the past, I took an instant very strong dislike to the effect. Donut bokeh won't appear in *every* image, but it will be particularly prominent in highlights on out-of-focus marine backgrounds, and that renders it useless (to me) for photographing waders, herons, gulls and other birds that frequent rivers, ponds or shorelines.
 

AlanF

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My suspicion is that these cats, if they actually get into production (which I doubt), would be rather more expensive than you think.
I don't think they'd be "budget" lenses in the same price band as e.g. the 600/11, 800/11 and 100-400/5.6-8, in fact it wouldn't surprise me if they were "L" standard weather-sealed lenses, with a hefty price tag to match.

I would envisage the primary target buyers as media agencies and paparazzi types, needing highly portable get powerful lenses to capture politicians, "celebrities" etc from a safe distance.

I may have misunderstood your final sentence, but having "donut" bokeh is inherent in the design. The reflector behind the middle of the front element will automatically produce a "hole" in the bokeh.

Having used mirror lenses in the past, I took an instant very strong dislike to the effect. Donut bokeh won't appear in *every* image, but it will be particularly prominent in highlights on out-of-focus marine backgrounds, and that renders it useless (to me) for photographing waders, herons, gulls and other birds that frequent rivers, ponds or shorelines.
Amusingly, you a Brit spell it "Donut" and Dragon who is in Oregon spells it "Doughnut"!
 
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neuroanatomist

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The secondary mirror is typically glued to the back of the front element. In this case, the front element appears flat and the diagram shows the light rays coming straight in to a mirror of the same diameter. I did not mean that the lens would not have doughnut bokeh, but rather that the front element would not be ground lens of doughnut shape, which is typical of most cats (and the mirror is typically smaller than the front element).
Sorry, but I think you are misinterpreting the diagrams. These are typical catadioptric lens designs. There are no light rays coming straight through, only two peripheral rays are shown (the central line is labeled OA for optical axis, that's not a ray diagram).

I suspect you believe the mirror is transparent or something like that (and there have been catadioptric using a half-silvered central spot on the back of the front element as the secondary mirror), but consider that a light ray passing through that central region of the front element then passing straight through to the lens elements behind the primary mirror (as that line labeled OA does) would not be reflected at all, and thus would lose about half the focal length compared to the reflected rays. Such rays could not be part of the final image. The patent mentions a ring-shaped entrance pupil.
 
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Dragon

EF 800L
May 29, 2019
628
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Sorry, but I think you are misinterpreting the diagrams. These are typical catadioptric lens designs. There are no light rays coming straight through, only two peripheral rays are shown (the central line is labeled OA for optical axis, that's not a ray diagram).

I suspect you believe the mirror is transparent or something like that (and there have been catadioptric using a half-silvered central spot on the back of the front element as the secondary mirror), but consider that a light ray passing through that central region of the front element then passing straight through to the lens elements behind the primary mirror (as that line labeled OA does) would not be reflected at all, and thus would lose about half the focal length compared to the reflected rays. Such rays could not be part of the final image. The patent mentions a ring-shaped entrance pupil.
Sorry, but somehow I am not getting through. All I am trying to point out is that the front element does not appear to be a "lens", but rather a cover glass. Many catadioptric telescopes are simply open around the secondary mirror. In this case, the cover glass would protect the interior from moisture and dust. In contrast, most cat camera lenses have a magnifying element around the secondary mirror.
 

Dragon

EF 800L
May 29, 2019
628
639
Another interesting oddity of these lenses is that the light rays cross the optical axis between the secondary mirror and the first lens element. This is effectively an image plane and means that the image at the specified image plane will be right side up and not inverted as is the case with normal camera lenses. This would cause the image in the viewfinder to be inverted unless the camera were programmed to not invert the image for these specific lenses.
 
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neuroanatomist

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Sorry, but somehow I am not getting through. All I am trying to point out is that the front element does not appear to be a "lens", but rather a cover glass.
I see. Still a donut, just not a 'lens'. The old supertele lenses (MkI) had a flat piece of protective glass as the first element.

Screen Shot 2022-03-28 at 11.59.59 PM.png
 
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SteveC

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Amusingly, you a Brit spell it "Donut" and Dragon who is in Oregon spells it "Doughnut"!
You might be surprised to hear this, but "doughnut "is actually the preferred spelling in the States...or at least it was until very recently. The language is changing, as languages do. I expect dictionaries to be slightly behind the times, but Merrian Webster (fairly authoritative in the States) still shows "doughnut" as more common. https://www.merriam-webster.com/dictionary/doughnut
 

AlanF

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You might be surprised to hear this, but "doughnut "is actually the preferred spelling in the States...or at least it was until very recently. The language is changing, as languages do. I expect dictionaries to be slightly behind the times, but Merrian Webster (fairly authoritative in the States) still shows "doughnut" as more common. https://www.merriam-webster.com/dictionary/doughnut
Oxford Dictionary: Definition of “common”
3 BRITISH
showing a lack of taste and refinement supposedly typical of the lower classes; vulgar.
"she's so common"
 

SteveC

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Oxford Dictionary: Definition of “common”
3 BRITISH
showing a lack of taste and refinement supposedly typical of the lower classes; vulgar.
"she's so common"
Fair enough, but I wasn't using the word "common" in that sense but rather the sense of more frequently used.

In any case, I am surprised that you seem to be implying that "doughnut" is more vulgar than "donut."
 

AlanF

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Fair enough, but I wasn't using the word "common" in that sense but rather the sense of more frequently used.

In any case, I am surprised that you seem to be implying that "doughnut" is more vulgar than "donut."
I am not implying anything, just joking that you are implying "doughnut" is more vulgar to highlight the imprecision of language! Anyway here are the data on frequency. Both donut and doughnut are more frequent in US than British English.


Screenshot 2022-03-29 at 17.43.12.png Screenshot 2022-03-29 at 17.42.30.png
 

SteveC

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I am not implying anything, just joking that you are implying "doughnut" is more vulgar to highlight the imprecision of language! Anyway here are the data on frequency. Both donut and doughnut are more frequent in US than British English.

Hah! Yes, a very imprecise language we have here. (Though with great care and a lot of wordiness precision can be achieved. Sometimes.)

I guess the conclusion here is that doughnuts themselves are more common here than in the UK.
 

neuroanatomist

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I guess the conclusion here is that doughnuts themselves are more common here than in the UK.
On a 4 mile stretch of the main east-west road running through my city, there are seven Dunkin’ Donuts locations, including a pair of them literally across the road from one another. So, yeah…apparently we’re nuts for donuts here.
 

Dragon

EF 800L
May 29, 2019
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I see. Still a donut, just not a 'lens'. The old supertele lenses (MkI) had a flat piece of protective glass as the first element.

View attachment 202894
Yes, still a doughnut but in my original post I was speaking to cost and the fact that the front glass was not a large lens, so thus the only large optical element in the entire design is the mirror. The old superteles actually had a flat piece of protective glass in front of the first element (sort of a "must have" clear filter), but they still had a very large actual first element. In the case of these cat designs, the flat glass is not replacing an optical element, but rather keeping dust and water out of the lens and it also provides support for the secondary mirror without the diffraction spike inducing support arms used in telescopes. I am not suggesting these lenses would be dirt cheap, but given the relative size of the elements, they could be MUCH cheaper than the current (or past) big whites. If the corrective lenses do a good job of correcting, the result could be very useful.
 
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