Canon RF 800mm F/11 IS STM Lens Review

This new lens from Canon extends its telephoto range for mirrorless cameras, and 800mm is pitching it firmly at long-range sports and wildlife photographers. These are big beasts at the best of times, and manufacturers make various compromises and decisions to mitigate the weight and difficulty of wielding such huge optics. Canon has decided to limit the aperture of the lens, in fact, to reduce the apertures on offer to just one, f/11, and the use of diffractive elements to reduce the amount of glass used. The lens also has a retractable construction, to reduce its size for transport. Is the f/11 aperture feasible in our varied and often dull climate? Is the quality of the images maintained with the simplified optical construction? Using the 45MP Canon R5 mirrorless full frame body, let's find out.

Canon RF 800mm f/11 IS STM Handling and Features

800mm lenses can be unwieldy, and the new lens is no exception to this. However, it is remarkably light at 1260g and remarkably compact, being 101.6mm in diameter, 281.8mm long when collapsed and 351.8mm long when fully extended for use. There is a generously sized lens hood that bayonets cleanly into position. This round hood does have a locking catch, so it remains secure in use. Within the bayonet fit for the hood is a conventional 95mm filter thread.

There is quite a long section of lens barrel before we reach the lens control ring, which, in normal Canon fashion, can be programmed to alter shutter speed, exposure compensation or ISO. A half pressure on the shutter release is needed to activate the ring for use. There are light click stops. There is no option for aperture control of course, as there is no diaphragm, just a fixed f/11 aperture that is totally round. Smooth bokeh is assured.

The wide manual focus ring is electronic and ultra-smooth. Perhaps it could do with a little more tension as it is very light in operation. It is possible to tweak the focus position after AF has been achieved. AF is driven by an STM motor, and this is virtually silent and moderately fast.

Normal advice for shorter lenses would be to get close and then closer, but with this 800mm lens the choice is to move further away and then further, as the closest focus is 6m, or 19.685 feet. The maximum magnification is a modest 0.14x. This is not very close.

The lens is compatible with the RF extenders though, so we can have greater magnification. Extender RF 1.4x results in an 1120mm f/16 lens with 0.19x magnification. Extender RF 2x results in a 1600mm f/22 lens with 0.28x magnification. The lens is not compatible with extension tubes.

Optical construction is 11 elements in 8 groups. Canon has opted to use diffractive elements in the lens, which reduce the weight considerably. Diffractive elements use diffraction gratings in front of the elements, somewhat similar to the Fresnel lenses used to even out light transmission in optical viewfinder systems. In lenses, this can be used to gain the advantages of fluorite glass and aspherical elements, to reduce aberrations and particularly to reduce CA. The potential downside is that such lenses may be more susceptible to flare. We shall see how this all works out in the Performance section.

There are three switches on the lens barrel. The first is the focus limiter, offering the choice of full range or a reduced range from 20m to infinity. The second is the AF/MF switch. The third is the stabiliser on/off switch. Canon claim 4 stops advantage when using IS, although if being used to photograph wildlife IS will do nothing at all to affect subject movement. If using a tripod, then it is recommended that IS is switched off, but if using a monopod it should be switched on.

At the same point on the lens barrel, there is a tripod mount, solidly incorporated into the barrel. As there is no conventional tripod handle with a swivelling collar, the lens cannot be easily turned for portrait format shots without turning the camera body as well.

Finally, there is a large locking collar that is used to lock the barrel either into its retracted or its extended position. Unfortunately, there is no weather sealing.

To get the best out of any 800mm lens we do need to be able to keep it steady. The 4-stop IS helps enormously, as does the relatively low weight. Hand-held shooting is possible and with a steady hand, images will be sharp. Using a monopod is another possibility, but then so is finding a support to hold the lens steady against, be it a wall, fence or post or whatever else can be found. A tripod with the head loosened is also excellent as a support, whilst offering some degree of movement for aiming. It really is down to practice though, and with some investment of time images will rapidly improve.