Patent: Canon RF 300mm f/2.8L IS 1.4x plus other supertelephoto optical designs

Canon Rumors Guy

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  • Jul 20, 2010
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    One of the most popular, if not the most popular “big white lens” is the Canon 300mm f/2.8L IS. We’re still waiting to learn more about an RF version of the lens. It’s our understanding that Canon has done a complete ground-up redesign for the RF 300mm f/2.8L IS USM.
    A new patent showing a bunch of super-telephoto optical designs has appeared, and all of these optical formulas come with a built-in 1.4x teleconverter.
    We think that a 1.4x built-in teleconverter would be quite welcomed on an RF 300mm f/2.8L IS USM.
    Canon RF 300mm f/2.8L IS USM 1.4x

    Focal length: 300.00mm
    F-number: 2.91
    Half angle of view: 4.12°
    Image height: 21.64mm
    Overall length: 320.00mm
    Back Focus: 49.68mm

    There are also 400mm, 500mm, 600mm and 800mm optical formulas in this patent.

    Continue reading...
     
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    Copying Nikon but in the best way possible. Flick in 1.4x TC are the best value add to the mirrorless big lenses and makes TC's much more usable and available in fleeting moments.

    I really want to see the first generation of big whites for the RF system, I have high hopes Canon put in the effort after the assuredly poor reception of the adapted EF/built in 2X TC lenses.

    300mm f/2.8 was one of my favourite lenses for a decade, though I have since moved on to 400 and 800 as preferred focal lengths. I would however love a 120-300f/2.8 TC to take along with a 400 f/2.8 TC or shove them both into one monster 100/200-400 f/2.8 TC.
     
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    Birdshooter

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    Copying Nikon but in the best way possible. Flick in 1.4x TC are the best value add to the mirrorless big lenses and makes TC's much more usable and available in fleeting moments.

    I really want to see the first generation of big whites for the RF system, I have high hopes Canon put in the effort after the assuredly poor reception of the adapted EF/built in 2X TC lenses.

    300mm f/2.8 was one of my favourite lenses for a decade, though I have since moved on to 400 and 800 as preferred focal lengths. I would however love a 120-300f/2.8 TC to take along with a 400 f/2.8 TC or shove them both into one monster 100/200-400 f/2.8 TC.
    Not at all, it is Nikon that copied Canon. We do have a 200-400 with built in TC, don't cha know?
    I and I am sure other would love Canon to bring out smaller super telephotos like Nikon has with the PF line as we had the DO line first as well. And if you, want to say Canon copied Nikon, it's your story tell it the way you want.
     
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    neuroanatomist

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    And if you, want to say Canon copied Nikon, it's your story tell it the way you want.
    People like to rewrite history to tell their own stories. Heck, even companies do. Like how Nikon copied Canon's use of fluorite lens elements.

    Today, their lens glossary states, "Fluorite is a monocrystal optical material that features a high transmission rate within both the infrared and ultraviolet zones. With its superb anomalous dispersion properties, fluorite intensely blocks the secondary spectrum in order to effectively correct chromatic aberration within the visible light spectrum – something that is more difficult to achieve at longer focal lengths. It is also significantly lighter than optical glass, giving you a more effective lens with less weight."

    But several years ago, before they introduced FL elements into their supertelephoto designs (about two decades after Canon started doing so, though in fairness Nikon has used fluorite in microscope objectives for decades), Nikon's lens glossary for entry ED elements stated, "In the past, correcting this problem for telephoto lenses required special optical elements that offer anomalous dispersion characteristics - specifically calcium fluoride crystals. However, fluorite easily cracks and is sensitive to temperature changes that can adversely affect focusing by altering the lens' refractive index."

    Now that they're using FL elements, they've updated their glossary entries to sing the praises of fluorite instead of only highlighting the weaknesses.
     
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    neuroanatomist

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    Since the subject of fluorite has come up, Nikon guy Them Hogan has stated quite strongly his belief Nikon's fluorite is sourced from Canon, as he knows of no other manufacturer of large diameter fluorite. So likely Sony is sourcing its fluorite from Canon, also. Profit is where profits are.
    Interesting. Could be they tried to produce them internally but weren't able to grow sufficiently large crystals. It's as much art as it is engineering.
     
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    MiJax

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    IMO, some lenses and some use cases lend themselves more to different TCs. For example, IMO, a 400mm is better suited with an internal 1.4x, but I'd argue a 500mm is much more useful with a internal 2.0x at 1000mm. On a 300mm I argue its pretty even between the two, but I'd love to see them seriously consider the internal 2.0x.
     
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    juststeve

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    My apologies to THOM Hogan. Corrected in my post. He is quite often an interesting read even for a Canon user as he has used Canons often enough to have a solid familiarity of strengths and weaknesses. He is not a rabid fan boy and is a highly competent photographer. As an aside, someday before I die, I hope to learn how to type. Not likely to happen, though.
     
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    xps

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    I hope, they do not do the same with the 300mm like with the 600mm III version. This is definitively not as sharp as the Mk II.
    I pray they keep optical quality like the 300mm, as IMO it is their sharpest prime lens.
    And the do not go higher than 10000 Euros. (Ok, this is wishful thinking. Realistically 12000 € as Canon knows how to milk us fanboys)
     
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