The RF 800mm F11 IS STM ($999.99) is the bigger, longer lens of a pair of ultra-telephoto primes for Canon's full-frame mirrorless camera system. It sports an extremely long focal length, perfect for bringing distant subjects into close view, and its F11 optics keep things lightweight. There are some drawbacks to consider, including the narrow, fixed aperture and limited focus coverage. It's an attractive lens for photographers searching for an affordable telephoto, but we think the RF 600mm F11 IS STM is a better starting point.

A Lot to Handle

Telephoto lenses are typically pretty big. Even at a F11 and with a retractable design, the RF 800mm is still a lot to handle. It measures 11.1 by 4.0 inches (HD) when closed down for storage, and extends to 13.9 inches when extended and ready for use. It's a lot of lens to hold, but at 2.8 pounds it's at least pretty light for its size. Extending the lens doesn't take much effort, either. A collar twists to lock and unlock the mechanism, and a simple push or pull is all you need to extend or collapse the optics.

It's more lens to handle than the smaller RF 600mm F11 IS STM. The two use the same basic design language and concept, but differ in focal length. The 600mm is smaller and lighter all-around (7.9 to 10.6 by 3.7 inches and 2.1 pounds), but doesn't provide as much magnification. You can see the difference in angle in the comparison below; the photos were taken minutes apart from the same position.

Because it's a pretty big lens, you'll want to think about how to carry your camera with it attached. Canon includes a standard tripod thread on the barrel, useful as an attachment point for photographers who use sling straps. It's also where you'll want to attach a quick release plate for use with a tripod.

The RF 800mm is made well, but not to pro standards. It uses sturdy plastics with a metal mount, and protects the front of the barrel with a leatherette wrap. It doesn't include dust, splash, or anti-smudge fluorine, and you'll have to spend an extra $54.95 if you want a hood. The front element supports 95mm filters.

There are a few on-lens controls. You get the expected manual focus ring, finished with the same rubberized ridges as most lenses. It abuts a control ring, useful for dialing in EV, ISO, and other adjustments. The ring is easy to spot thanks to a metallic silver finish, and you can find its diamond-pattern texture by touch. It clicks for precise adjustments, but you can have the ring converted to silent, click-free operation if you'd like (for an extra $80 to the cost, and you'll have to send it in to Canon for service).

There are some on-lens toggle switches too. You get an AF/MF switch to change focus modes, a focus limiter switch, and an optical stabilization switch. Autofocus is quiet, but not as fast as pro lenses with USM motors, like the $2,900 RF 100-500mm. It led to a few more missed shots in the field than I'd expect with the EOS R5, but only a few. For the most, part results were spot-on.

The real limiting aspect of focus is the coverage area. Most lenses focus to near the edges of the frame with Canon's mirrorless cameras. The F11 optics limit the scope of coverage to the center of the frame, as shown above.

Getting too close to what you want to photograph is a concern too. The RF 800mm can't focus closer than about 20 feet (6 meters). It's typical for a prime (Canon's high-end EF 800mm F5.6 for SLRs has the same limitation), but zooms do tend to get better macro results. On the other hand, you won't get as far a telephoto reach from a zoom lens. A limiter switch is included for times when you know you'll be tracking distant subjects, at least 66 feet (20m) from camera.

At best, the RF 800mm nets 1:7.1 life-size reproduction, similar to what you get from the RF 600mm at its nearest focus distance. To enjoy both close focus and telephoto in one lens, you'll need to shop for a zoom, and budget a bit more in the process. The RF 100-500mm L is the only native long zoom for the system and gets 1:3 macro focus, but comes with L series pricing ($2,900).

Optical stabilization is included, which is important for a long telephoto lens. It's especially vital if you're using a camera without sensor stabilization, like the first-gen EOS R and entry-level EOS RP. The lens is able to net blur-free shots at handheld speeds as long as 1/30-second in our testing.

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Teleconverters are supported, but you should only think about adding them when working under bright skies. The RF 800mm supports both the RF 1.4x ($500) and RF 2.0x ($600) extenders, but the longer focal lengths come at a cost. With the 1.4x extender, the lens is an 1,120mm F16. With the 2.0x, it's a 1,600mm F22. At those f-stops, you'll push the ISO high even on sunny days.

Lab and Field Testing

The lens has some appeal to entry-level customers, so we wanted to test it on a camera closer in resolution to the 26MP EOS RP. I paired the RF 800mm with the 45MP EOS R5 in the field, and ran lab tests with both the R5 and 30MP EOS R.

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The lens delivers just-okay results with the high-end R5, not surprising given just how far Canon has flexed its muscles to deliver 800mm of focal length in an affordable, stabilized, full-frame lens. It nets about 2,750 lines of resolution in the central area of the frame, producing softer details when compared with the RF 600mm (3,500 lines).

The optics are a better match for lower resolution sensors. The EOS R shows nearly as much central resolution at 2,600 lines, within the very-good range for a 30MP full-frame camera. It's a sign that the glass simply doesn't maximize the potential of the high-resolution R5.

Bokeh quality is generally pleasing. The optics avoid the donut-hole bokeh look you get with manual focus mirror lenses. Defocused highlights are circular toward the center of the frame, but take on a cat's eye shape toward the edges of your image. The lens doesn't have an adjustable aperture, so you're set using it at F11 full-time.

Lotsa Lens

The RF 800mm F11 IS STM is uniquely positioned in the market, a $1,000 prime that nets the same angle of view as high-end lenses that cost thousands more (the EF 800mm F5.6L for SLRs is positioned at $13,000). Because of this, Canon mirrorless owners looking for a lens with big magnification power should consider it.

The RF 800mm isn't nearly as high-end as the EF 800mm, but it's still made well, has optical stabilization, and includes upmarket features like a control ring and on-barrel toggles. The optics aren't up to the standards of high-end, multi-thousand dollar lenses, either, which is an understandable compromise. It's also a big lens, even when retracted.

Canon's similar RF 600mm F11 IS STM gets a slightly stronger recommendation. It doesn't have quite as tight an angle of view, but is smaller all around and its optics are a little bit sharper. At around $800, it costs a bit less, too.

Neither the RF 800mm nor the RF 600mm F11 are as good as Canon's L series mirrorless telezoom, the $2,900 RF 100-500mm F4.5-7.1 L. There's no affordable telezoom on sale for the EOS R system at press time, but don't forget about the venerable Sigma 150-600mm Contemporary for SLRs, compatible using the EF-EOS R adapter. It's on sale for around $1,000 today, and remains our top recommendation for photographers shopping for an affordable, full-frame telezoom.

Thanks to LensrentalsLensrentals for providing teleconverters for this review.