The Canon RF 100-400mm f/5.6-8 IS USM offers a slightly slower, but a lot smaller, lighter, and cheaper alternative to the excellent Canon RF 100-500mm f/4.5-7.1 IS USM lens.
Despite being launched alongside the formidable Canon EOS R3 (and the Canon RF 16mm f/2.8 STM) this isn't a professional L-series lens, but instead brings a similar degree of telephoto reach to non-pro shooters – and in a more compact form factor that's a better fit for smaller bodies like the Canon EOS R6, with which it pairs well.
The price is definitely a key factor with this optic; it's no secret that RF lenses haven't come cheap until recently, as Canon initially focused on premium-grade glass to show what the EOS R system can do, with only seven of the twenty-three RF lenses coming in at under a grand.
Obviously the biggest question with this lens lies in its aperture. With a gearbox that only shifts between f/5.6 and f/8, can this really deliver for the sports, wildlife and all-purpose shooters at whom its aimed?
Canon RF 100-400mm f/5.6-8 IS USM: Specifications
Mount: Canon RF
Full frame: Yes
Lens construction: 12 elements in 9 groups
Diaphragm blades: 9
Minimum aperture: f/32 at 100mm, f/45 at 400mm
Closest focusing distance: 0.88m
Maximum magnification: 0.41x
Filter size: 67mm
Weather sealed: No
Stabilization: Yes, 5.5 stops (6 stops with IBIS bodies)
Control ring: Yes
Electronic contacts: Yes
Dimensions: 79.5 x 164.7mm (247mm when extended to 400mm)
Canon RF 100-400mm f/5.6-8 IS USM: First impressions
The RF 100-400mm f5.6-8 IS USM is remarkably small, especially when compared to the Canon EF 100-400mm f/4.5-5.6L IS II USM DSLR lens. Its footprint is about 28% smaller, and it's a little over a kilogram lighter, though the variable aperture range is a little more restrictive than the EF lens.
The new compact RF lens doesn't get Canon's prestigious L-series treatment, so it doesn't feature full weather-sealing or a rubber seal around the lens mount to keep water and dust out. That said, it is an unquestionably light, small and feature-dense optic and when paired to one of Canon's equally portable EOS R mirrorless cameras and you have a very compact and capable system.
The 4x optical zoom takes you from short telephoto 100mm f/5.6 zooming all the way into 400mm where the aperture closes down to f/8. Also built-in is Optical Image Stabilization, which Canon claims will enable you shoot at shutter speeds 5.5 stops slower than usually required to eliminate camera-shake from handholding.
The lens can also be used in tandem with the in-body stabilization of the Canon EOS R5, R6 and R3, with Canon claiming that this takes you to a 6-stop advantage.
The telephoto lens is constructed from 12 elements arranged in 9 groups and the aperture has a 9-blade design, so should deliver smooth circular bokeh in out-of-focus highlights. At its widest focal length the lens measures just 164.7mm, and extends to 247mm when zoomed to the maximum 400mm focal length.
There is a lens lock on the barrel that can be set to stop the barrel creeping forward at the 100mm mark. This is useful when you're stowing the lens away to travel – though it would have been nice to be able to lock it into focal lengths such as 135mm, 200mm, 400mm and so on, if you intend to shoot at a specific focal length for long periods.
Also on the side of the lens you'll find switches for auto / manual focus, and another switch to engage or disengage the Optical Image Stabilization. There are also large and grippy zoom and focus rings, with a ridge in the zoom ring that makes it easy to find and turn when looking through the viewfinder.
There's also the RF Control Ring closest to the front element that, after setting up in the camera menu, can be used to quickly change shutter speed, lens aperture, ISO or Exposure Compensation.
Canon RF 100-400mm f/5.6-8 IS USM: Early verdict
We only had the chance to shoot a few samples in less-than-ideal indoor conditions, so we'll have to save proper impressions for when we get a sample to test properly out in the field.
Initial impressions, though, are that the Canon RF 100-400mm f/5.6-8 IS USM is a very capable performer that behaves somewhat similarly to the Canon RF 24-240mm f/4-6.3 IS USM, insofar as it delivers excellent reach and seemingly excellent image quality. And, thanks to the impressive high-ISO performance of the EOS R cameras, that slow f/8 aperture isn't the hindrance you might expect.
Like the RF 100-500 before it, we suspect that AF performance will be notably superior on the R5 and R6 (and the R3), but with a $649.99 / £699 / AU$1,379 price tag this is an almost irresistible telephoto lens that democratizes long-range shooting with Canon glass.
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