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Canon has submitted a patent application in Japan for a series of fast, supertelephoto prime lenses that reduce the size of the current EF and RF versions of the 300mm f/2.8, 400mm f/2.8 and 500mm f/4.
RF 400mm f/2.8L IS USM II
The 400mm f/2.8L IS USM in this optical design is down about a 2cm in length. There is no weight given in these sorts of patent applications, but a reduction in size usually comes with some weight savings.
Going back to 1991 when Canon released the EF 400mm f/2.8L USM, it tipped the scales at 6.45kg / 14.2lbs. The current RF 400mm f/2.8L IS USM is down to 2.9kg / 6.3lbs. The current Sony 400 f/2.8 GM weighs about the same as the Canon offering.
Of the three optical designs, I believe the 400mm f/2.8L IS USM is the most likely to become a product.
We do know that both the RF 400mm and RF 600 “big whites” will be updated some time in 2026.
RF 300mm f/2.8L IS USM II & RF 500mm f/4L IS USM
During the EF days, we had both the EF 300mm f/2.8L IS USM II and EF 500mm f/4L IS USM II, niether of which exists in the RF lineup.
Canon instead chose to release the brilliant RF 100-300mm f/2.8L IS USM, but we're still waiting on some kind of 500mm f/4 lens. We do believe that it will also be a zoom lens of some kind and that Canon will keep the big primes to 400mm, 600mm and longer.
The EF 300mm f/2.8L IS USM II was 248mm / 9.8″ long, and in this optical design Canon has reduced the length down to 220mm / 8.6″ once flance distance is calculated. The current zoom version of the lens is very close in size.
The optical design here for the RF 500mm f/4L IS USM doesn't reduce the length of the lens all that much.
JPO 2025114982 Embodiments
| Canon RF 300mm f/2.8L IS | Patent: JPO 2025114982 |
|---|---|
| Focal Distance | 289.77 |
| F-number | 2.91 |
| Half Angle of View | 4.27° |
| Image Height | 21.64mm (Full-Frame) |
| Total Lens Length | 240.23mm / 9.45″ |
| Backfocus | 37.97mm |
| Canon RF 400mm f/2.8L IS | Patent: JPO 2025114982 |
|---|---|
| Focal Distance | 387.99mm |
| F-number | 2.91 |
| Half Angle of View | 3.19° |
| Image Height | 21.64mm (Full-Frame) |
| Total Lens Length | 366.59mm / 14.4″ |
| Backfocus | 38.51mm |
| Canon RF 500mm f/4L IS | Patent: JPO 2025114982 |
|---|---|
| Focal Distance | 543.19mm |
| F-number | 4.12 |
| Half Angle of View | 2.28° |
| Image Height | 21.64mm (Full-Frame) |
| Total Lens Length | 372.05mm / 14.6″ |
| Backfocus | 38.30mm |
Photo by Tim Mossholder on Unsplash
On the other hand, the overall diagram looks pretty much identical to the 300mm lens with a tele group added, but the math there doesn't really work out for 1.4 or 2x
And I also want a leight weight 300 2.8.
Maybe Canon is doing the same thing as with the RF 800mm f5.6 and RF 1200mm f8: add a teleconverter to an existing design to create a ‘new’ lens.
I remember reading that we should be expecting a new totally redesigned 400 and 600 just before the Olympics in February 2026
100-300/2.8
400/2.8
600/4
800/5.6 & 1200/8 = 400/600mm + internal fixed TC.
100-500/4.5-7.1
The EF L lineup was introduced over a much longer time vs 7 years for RF lenses so far. Have I missed any?
The question for me is what volumes of these would be significant or profitable vs the current RF list?
70-300/4-5.6 => Not great quality
28-300/3.5-4.5.6 => Not great quality
300/2.8 (2.5kg/250mm) => Cheaper and shorter but almost the same weight as RF100-300/2.8 (2.6kg/325mm).
300/4 (1.2kg)=> No equivalent
400mm f/4 DO ii => No equivalent
500/4 => Would users buy this vs 400/2.8 or 600/4?
200-400/4 + TC => Heavy, big and expensive
Given the tech advances in high ISO dynamic range, full sensor AF, AF focusing at much smaller apertures and new optical design sharpness then are the non-L RF long lenses sufficient? Clearly Nikon/Sony have additional or different long lenses but I am less convinced that the current
100-400/5.6-8
200-800/6.3-9
600/800/f11
All that I can see that is missing is a light weight and cheap(ish) 300/4. Maybe a DO 500 or 600mm/5.6. Maybe a 200-500+TC.
Thoughts??
Nikon has a few great lightweight long tele primes, at least one using their PF technology. Not everyone wants or can afford the large teles, but many would like more light gathering than the tele zooms.