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    Canon Patent Application: RF Super Telephotos

    By Updated:19 Comments2 Mins Read Canon Patents
    JPA 506009238 i 000004 1536x518 - Canon Patent Application: RF Super Telephotos

    In this patent application (2024-009238) we have a series of telephoto primes for the RF mount. We know these are specifically for the RF mount because the back focus distance is under 44mm. Also, with a more relaxed back focus distance (greater than 20mm) they should work with Canon's tele-extenders.

    While the current RF super telephotos have been out for a while, we haven't seen any specific RF designs used yet for the big whites. It's pretty early for Canon to replace the big whites so I wouldn't necessarily expect any of these designs to end up on a lens soon, but Canon has surprised us in the past. Remember that Canon's 1 series flagship is expected to be coming out sometime this year and that it's an Olympic year so anything is possible.

    Canon RF 400mm F2.8

    Focal length        392.00
F number              2.90
Angle of view         3.16 
Image height         21.64
Lens total length   360.03
BF                   31.01

    Canon RF 500mm F4.0

    Focal length        490.00
F number              4.12 
Angle of view         2.53 
Image height         21.64
Lens total length   412.08 
BF                   33.39

    Canon RF 600mm F4.0

    Focal length        588.00
F number              4.12
Angle of view         2.11 
Image height         21.64
Lens total length   476.08
BF                   33.21

    As with all patent applications, this may never end up in an actual patent or products but it's a look inside of Canon's research.

    Japan Patent Application 2024-009238

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    19 comments

    2. so I wouldn't necessarily expect any of these designs to end up on a lens soon

      You actually have a Canon RF 500mm f/4L IS USM on "your own" roadmap:

      www.canonrumors.com

      Canon RF lens roadmap

      This is the Canon RF lens roadmap for the next couple of years. I will be updating this list as new information comes in. Canon RF-S Lenses Canon RF-S 10
      www.canonrumors.com

      Though, my guess so far is that the also rumoured Canon RF 200-500mm f/4L IS USM is meant to replace a 500mm f/4 L prime, just as Canon also considers the Canon RF 100-300mm f/2.8L IS USM as a replacement for a 300mm f/2.8 L prime.

      But, well...
    3. You actually have a Canon RF 500mm f/4L IS USM on "your own" roadmap:

      www.canonrumors.com

      Canon RF lens roadmap

      This is the Canon RF lens roadmap for the next couple of years. I will be updating this list as new information comes in. Canon RF-S Lenses Canon RF-S 10
      www.canonrumors.com

      Though, my guess so far is that the also rumoured Canon RF 200-500mm f/4L IS USM is meant to replace a 500mm f/4 L prime, just as Canon also considers the Canon RF 100-300mm f/2.8L IS USM as a replacement for a 300mm f/2.8 L prime.

      But, well...
      Unless Canon releases both options, a zoom and a worthy prime upgrade too.
      The current RF 400mm f2.8 LIS is actually softer than the EF 400mm f2.8 LIS mkII, so maybe Canon can match the heady IQ of the EF mkII version?
    6. Softer is a relative term. Compare the lenses with extenders and it might surprise you.
      RF is definitely softer with the 2x, but that aligns with experience that the EF 2xIII is better than the RF 2x (on the same lens).
    7. Really?
      www.the-digital-picture.com

      Canon EF 400mm f/2.8L IS II USM Lens Image Quality

      View the image quality delivered by the Canon EF 400mm f/2.8L IS II USM Lens using ISO 12233 Resolution Chart lab test results. Compare the image quality of this lens with other lenses.
      www.the-digital-picture.com www.the-digital-picture.com
      If this shows a "softer lens" maybe I'll need new glasses ;)
      Me too!
      What I see are two absolutely identical sharpness results...at least without extenders.
      And even with the 2X extender, the RF looks even a bit better.
    9. Me too!
      What I see are two absolutely identical sharpness results...at least without extenders.
      And even with the 2X extender, the RF looks even a bit better.
      Canon's own MTF charts have the EF 400mm f/2.8 II slightly sharper than the RF 400mm f/2.8.

      EF_II_MTF400.png400_III.png
    11. EF 400 vs. RF 600 :unsure:...
      But when both 400mm were being compared, was it using the same method?
      Canon's MTFs are calculated from the lens design, they aren't empirically measured. They did change the way they calculate the MTFs some time back and old can't be compared to new, but they're easy to tell apart since the old ones have 8 lines and the new ones have 4 lines.

      Since the MTFs are theoretical / best case, production lenses may not all be the same or as good.
    12. EF 400 vs. RF 600 :unsure:...
      But when both 400mm were being compared, was it using the same method?
      Oops - posted wrong curve. Now corrected. The ii is a little sharper than the iii. They should get better not worse. But, the sacrificed optics for weight.
    13. Canon's MTFs are calculated from the lens design, they aren't empirically measured. They did change the way they calculate the MTFs some time back and old can't be compared to new, but they're easy to tell apart since the old ones have 8 lines and the new ones have 4 lines.

      Since the MTFs are theoretical / best case, production lenses may not all be the same or as good.
      The big change was that in the past they did not include diffraction.
    14. They did change the way they calculate the MTFs some time back and old can't be compared to new, but they're easy to tell apart since the old ones have 8 lines and the new ones have 4 lines.
      The 2nd set of four was for stopped down to f/8. A bit difficult to do for the RF 200-800mm at the long end...
    15. The 2nd set of four was for stopped down to f/8. A bit difficult to do for the RF 200-800mm at the long end...
      Yes, in retrospect it’s pretty clear that the change was made when lenses slower than f/8 were put on the internal product map.
    17. Yes, in retrospect it’s pretty clear that the change was made when lenses slower than f/8 were put on the internal product map.
      It would be more helpful if the 2nd curve was based on each lens stopped down 2 stops instead of the arbitrary F8, which for some lenses could be wide open!
    18. Yes, in retrospect it’s pretty clear that the change was made when lenses slower than f/8 were put on the internal product map.
      That makes sense...but I also wonder if the shift is the fact that lenses tend to no longer be sharpest at f/8....rather wide open is actually sharper than f/8. Just as I recently plotted this, but Optical Limits observed 5,119 LW/PH at f/2, 5,350 LW/PH at f/2.8, and 4,665 LW/PH at f/8 for the RF 28-70 f/2 (all on the R5).

      f/8 values used to indicate the top performance of the lens....now, the best performance is usually within 1/3 to 1 stop of wide open. Thus, f/8 lines are unnecessary.
    19. That makes sense...but I also wonder if the shift is the fact that lenses tend to no longer be sharpest at f/8....rather wide open is actually sharper than f/8. Just as I recently plotted this, but Optical Limits observed 5,119 LW/PH at f/2, 5,350 LW/PH at f/2.8, and 4,665 LW/PH at f/8 for the RF 28-70 f/2 (all on the R5).

      f/8 values used to indicate the top performance of the lens....now, the best performance is usually within 1/3 to 1 stop of wide open. Thus, f/8 lines are unnecessary.
      I think the old f8 scoring was intended for the older UWL. They all sufffered from field curvature / soft extream corners. The increase in DOF to F8 ( from F2.8 or F4) usually was enought to bring the curved focus plane into focus and more sharp. It wasn't until the ef 16-35 LIS and the EF 11-24L came a long and shows us what a better attempt at flat field could do for us in the far corners.

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