Hands-on with new Canon RF 400mm F2.8 / 600mm F4L I.S.

Canon has announced two new telephoto prime lenses for the RF mount. The RF 400mm F2.8L IS USM and 600mm F4L IS USM have the same optical makeup as their EF-mount equivalents, which were released relatively recently, in late 2018.

Click through for a closer look at these two new telephoto options for RF.

Optical makeup

Optically, the new RF 400mm and 600mm F2.8 are identical to their EF counterparts, with 17 elements in 13 groups, including one Super UD and two fluorite special elements, along with Super Spectra and Air Sphere coatings. The big news when the EF versions were announced in late 2018 was their weight, or rather their lack thereof: both lenses were around 1kg (~2 lbs) lighter than their Mark II predecessors. The new RF versions are fractionally heavier, but it’s a matter of 40-50 grams.

The new RF lenses are also slightly longer, to account for the shorter flange-back of the RF mount. The ‘extension’ compared to the EF versions is finished in a glossy bare metal.

Same optics, new mount

Here’s a closer look at the finish of the 600mm F4L’s mount. The shiny metal also helps to quickly distinguish the RF version from its otherwise identical EF counterpart.

Will these new RF telephotos will offer superior performance on RF bodies compared to the EF versions with an adapter? Maybe...

While the communication protocols for EF and RF are similar, the RF standard uses 12 contacts (an increase from 8 for EF) and Canon claims that data throughput is faster than EF. As such, data should in theory move faster between camera and lens in an RF camera + RF lens combination, compared to an RF camera + adapter + EF lens combo. This may pay off in aspects of performance such as superior autofocus accuracy at very high frame rates, but we’ll have to wait and see.

Focus and customization options

Both of these lenses are designed for professional sports and wildlife work, but that doesn’t mean that they’ll only be pointed at distant subjects. The minimum focus distance on the 400mm F2.8 is 2.5m (8.2 ft) and 4.2m (13.8 ft) on the 600mm F4. The maximum magnifications are a useful 0.17x and 0.15x, respectively.

As we’d expect from professional-grade sports telephoto lenses, both lenses offer a degree of customization, with programmable focus hold buttons, limiters to restrict the focusing range to reduce hunting, and a focus preset option that allows you to ‘snap’ a control ring left or right to immediately jump to a pre-programmed focus distance. That focus preset ring can also be used to manually focus the lens in ‘PF’, or power focus, mode. The extent to which you turn the ring varies the speed of the electronically-driven focus, while the direction you turn it dictates whether focus shifts toward or away from the camera.

One control point that’s conspicuously absent from the RF 400 and 600mm lenses is a Control Ring of the kind that we’ve become used to seeing in native RF glass. Presumably this decision was taken with an eye to manufacturing efficiencies (keeping the EF and RF lenses as similar as possible).

5.5EV of optical image stabilization

Canon claims that the optical I.S. systems in the new 400mm and 600mm reduce camera shake by up to 5.5 stops regardless of which RF-mount body you’re using. This means that you won’t see any I.S. performance benefit from shooting on a newer Canon RF body with in-body image stabilization like the R5, R6 or the forthcoming R3. This is presumably because they were developed alongside the EF versions, which predate Canon’s in-body IS system and the protocol through which in-lens and in-body IS can work collaboratively.

For extra reach, both also support Canon’s RF 1.4x and 2x teleconverters.

Weather-sealing and signature white finish

As with all Canon L-series lenses, the 400 and 600 are rugged and weather-sealed, and have a fluorine coating on the front element to repel oil and water. Here you can see the 400mm F2.8L I.S with its included hood attached. At the extreme right, on the top of the lens barrel you’ll see one of the two sprung silver buttons which unlocks a tray for drop-in filters.

Final thoughts

There has been some confusion in DPReview comment threads about why these lenses even exist, when they’re optically identical to the existing EF versions, which can easily be adapted to RF bodies. There are two likely answers. One is that as lenses designed specifically for professional use, the addition of an adapter (an additional point of failure) may have been considered undesirable. Not to mention the cludge of having an adapter stacked with an RF 1.4X or 2X teleconverter, when extra reach is required.

The second explanation is that Canon developed these optical formulations from the beginning with the intention of using the designs for both EF and RF lenses. It’s probably not a coincidence that the original EF versions were launched alongside the original EOS R.

This ‘same glass but dual mount’ approach minimizes the need for additional tooling and helps keep costs under control. As for why the EF versions became available 2 years ago, well, maybe that’s just when they were ready.

The RF 400mm F2.8L and 600mm F4L are almost ready, and will be available in July priced at $12,000 and $13,000, respectively.

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