This is more for your curiosity because this isn't for an upcoming product, but one in which has already been released by Canon. But some of you may be interested in seeing some of the background that goes into making such a lens in the Canon universe.

This patent application (2024-062200) shows the RF 200-800mm F6.3-9.0 IS USM as an embodiment with the same element organization as the actual production lens.

Canon in this patent application described its objective as;

In recent years, imaging optical systems used in imaging devices are required to be small and lightweight zoom lenses that have a long focal length at the telephoto end and have high optical performance over the entire zoom range as a zoom lens whose telephoto end has a long focal length.

We can see from the patent application as well, that it was designed to be used with a teleconverter because the back focus distance is more relaxed than normal for an RF lens.

Canon RF 200-800mm F6.3-9.0 IS USM

                   Wide     Middle     Telephoto
Focal length 203.00 390.84 776.00
F number 6.42 7.30 9.18
Half angle of view 6.08 3.17 1.60
Image height 21.64 21.64 21.64
Lens length 331.63 390.98 421.61
Back Focus 37.98 61.62 96.27

Also shown as an embodiment, is a 200-500mm lens which is nearly the same size as the 200-800mm, this I think has a next to zero chance of making it into a future lens.

                   Wide     Middle     Telephoto
focal length 203.01 395.08 500.04
F number 6.43 8.04 9.18
half Angle of view 6.08 3.13 2.48
Image height 21.64 21.64 21.64
Lens length 321.37 404.17 420.39
BF 37.99 62.27 74.98

This is one patent application I can happily state made it to production.

Japan Patent Application 2024-062200

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16 comments

  1. So, it should be advertised as a 200-776mm lens. I know all manufacturers do this, but how can it be legal to mis-represent a product by this much?
    If you advertised a used lens for £$800, would you just take £$776, no questions asked?
  2. So, it should be advertised as a 200-776mm lens. I know all manufacturers do this, but how can it be legal to mis-represent a product by this much?
    If you advertised a used lens for £$800, would you just take £$776, no questions asked?
    Lens focal lengths are started with a degree of tolerance (usually 5%) which this is comfortable inside — 776mm is 3% less. At the end of the day the difference between 776 and 800mm is absolutely tiny. It's the same as the difference between a 50mm lens and a 50.1mm lens.
  3. So, it should be advertised as a 200-776mm lens. I know all manufacturers do this, but how can it be legal to mis-represent a product by this much?
    Also consider that focal length is measured at infinity focus. With closer focus distances, focus breathing results in an even shorter effective FL.
  4. Lens focal lengths are started with a degree of tolerance (usually 5%) which this is comfortable inside — 776mm is 3% less. At the end of the day the difference between 776 and 800mm is absolutely tiny. It's the same as the difference between a 50mm lens and a 50.1mm lens.
    3% of 50mm is 1.5mm, not 0.1mm. So, it's the same as the difference is between a 50mm lens and a 51.5mm lens. As the actual length is less than quoted, it's more appropriate, as well as accurate, to write it's the same as the difference is between a 50mm lens and a 48.5mm lens.
  5. Actual f/#’s always just a touch darker too. Never brighter. Of course no marketing person worth their salt would ever round down.
    They rounded down 9.18 to 9.
  6. 3% of 50mm is 1.5mm, not 0.1mm. So, it's the same as the difference is between a 50mm lens and a 51.5mm lens. As the actual length is less than quoted, it's more appropriate, as well as accurate, to write it's the same as the difference is between a 50mm lens and a 48.5mm lens.
    Won't there be focus breathing as well?
    edit never mind, Nero mentioned it.
  7. Won't there be focus breathing as well?
    edit never mind, Nero mentioned it.

    The focal length of the 800mm at the mfd is 458mm, as I have posted earlier.

    I calculate for a magnification of 0.2 at an mfd of 3300mm at 800m (remember they calculate mfd distance from the sensor) that the apparent centre of lens to object is 2750mm, the image 550mm to give an effective focal length of 458mm.

    For comparison, the RF 100-400mm is 212mm at 1050mm mfd, RF 100-500mm is 224mm at 1194mm.
  8. 3% of 50mm is 1.5mm, not 0.1mm. So, it's the same as the difference is between a 50mm lens and a 51.5mm lens. As the actual length is less than quoted, it's more appropriate, as well as accurate, to write it's the same as the difference is between a 50mm lens and a 48.5mm lens.
    I was refering to AoV change not mm change since the relationship is not linear. The change in angle of view between 800mm and 776mm is 0.1 degrees - Which is the roughly the same as the difference between 50mm and 50.1mm
  9. They rounded down 9.18 to 9.
    9.18 (actual) is darker than 9 (labeled). Rounding down, to me, would be to the next darker setting. F/9.18 rounded to f/10 for example.

    I know numerical 9 is down from 10. But with aperture, one steps down from 9 to 10. And since the actual physical iris would be a smaller diameter in that case - I support my way of thinking on this.
  10. Ah yes, life was simpler before calculators. I still have my engineering slide rule ;) from back in the day when 1 or 2 digits and a power of 10 was sufficient for a lot of things and 3 digits was a stretch. My neighbor in the concrete business lamented customers with their plotted plans that expect concrete poured to quarter-inch tolerances when the forms will bow more than that.

    Even now, most people I run into want things in relatable, ballpark terms like 750 or 800, not 776. The details usually come out only when comparing detailed specifications, and most of the time there really isn't a significant difference.

    I treat all focal lengths and f-stops as "around x". Life is easier this way.
  11. Ah yes, life was simpler before calculators. I still have my engineering slide rule ;) from back in the day when 1 or 2 digits and a power of 10 was sufficient for a lot of things and 3 digits was a stretch. My neighbor in the concrete business lamented customers with their plotted plans that expect concrete poured to quarter-inch tolerances when the forms will bow more than that.

    Even now, most people I run into want things in relatable, ballpark terms like 750 or 800, not 776. The details usually come out only when comparing detailed specifications, and most of the time there really isn't a significant difference.

    I treat all focal lengths and f-stops as "around x". Life is easier this way.
    Many of us are not "most people" when it comes to the technical details of our photography equipment.

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