Canon RF 100-400mm f/5.6-8 IS USM lens

      Photo Review 8.9

      In summary

      The RF 100-400mm f/5.6-8 IS USM is a lens many owners of Canon’s EOS R cameras have been waiting for.

      Although not particularly fast, it has a winning combination of light weight, easy handling, sharp focusing and a competitive price tag.

      Since the latest cameras can deliver high image quality at high ISO settings, fast lenses are no longer as essential as they were back in the DSLR era. And for photographers and videographers who have to be on the move for long periods of time, a lightweight lens is great to use. The only potential negative is the lack of weather resistance.

      Full review

      Since Canon launched its two lightweight, stabilised f/11 prime lenses about 18 months ago, many photographers have come to realise lens speed is not the be-all and end-all it was back in the days of film – or even DSLR photography. Today’s mirrorless cameras can offer far superior high ISO performance so it makes sense to work on two of the bugbears of fast telephoto lenses: heavy weight and high cost. The new Canon RF 100-400mm f/5.6-8 IS USM lens addresses both of those problems very handsomely.

      Angled view of the Canon RF100–400mm f/5.6–8 IS USM lens. (Source: Canon.)

      It’s important to understand that the 100-400mm lens is not a fast lens; although it is a very capable one in the right hands. The maximum aperture at 100mm is f/5.6, which changes to f/6.3 at around 123mm, stopping down to f/7.1. at 156mm and ending up at f/8 between 259mm and 400mm. Minimum apertures range from f/22 to f/45 (but it’s not worth stopping down beyond f/22 due to the effects of diffraction).

      This diagram shows the structure of the Canon RF100–400mm f/5.6–8 IS USM lens. (Source: Canon.)

      The optical design (shown above) contains 12 elements in nine groups, with specialised elements to control a variety of aberrations. One Ultra-low Dispersion (UD) element is located towards the front of the lens, where it suppresses chromatic aberrations and colour fringing, while a single aspherical element towards the rear helps to control distortion.

      Proprietary Super Spectra Coating has been applied to minimise flare and ghosting and improve contrast and colour fidelity in backlit situations. Built-in optical stabilisation claims up to 5.5 stops of camera shake correction in cameras without In-Body Image Stabilisation (IBIS), or 6 stops of stabilisation with the Coordinated Optical Image Stabiliser and IBIS.

      Autofocusing is driven by a ring type ultrasonic motor (USM) and stepping motor (STM) mechanism, which combine to provide fast, accurate focusing that is also smooth and near silent to suit video shooting. Close focusing capabilities are very good for such a long lens, as shown in the table below, which indicates the minimum focus and magnification ratios at the main focal length settings.

      Focal length Minimum focus Magnification
      100mm 1.2 metres 0.09x
      200mm 0.88 metres 0.24x
      300mm 0.95 metres 0.34x
      400mm 1.05 metres 0.41x

      The lens is supplied with front and end caps – but the lens hood is an optional extra. For the first time in a non-L-series lens, this lens will accept optional Canon RF 1.4x and 2x tele extenders. The effects of fitting the extenders are show in the tables below.

      RF1.4x Wide Tele
      Focal length 140mm 560mm
      Aperture range f/8-45 f/11-64
      Angle of view Horizontal 14o 40’ 3o 40’
      Vertical 9o 50’ 2o 25’
      Diagonal 17o 35’ 4o 25’
      Maximum magnification 0.12x 0.58x


      RF2x Wide Tele
      Focal length 200mm 800mm
      Aperture range f/11-64 f/16-91
      Angle of view Horizontal 10o 00’ 2o 35’
      Vertical 7o 00’ 1o 40’
      Diagonal 12o 00’ 3o 05’
      Maximum magnification 0.18x 0.83x

      We carried out all of our tests with the lens on the Canon EOS R3 camera, which is reviewed separately. (INSERT LINK)

      Who’s it For?
      Most buyers of this lens will be looking towards using it for sports and wildlife photography (including birding), where its light weight and superior stabilisation will allow hand-held shooting. Its compact size and inconspicuous nature will also make it suitable for documenting community events.

      Portrait photographers could find it handy as well since the 100mm focal length provides a flattering perspective and comfortable working distance while working with subjects. The rounded, nine-bladed iris diaphragm will contribute to a pleasing bokeh quality.

      Landscape photographers will be able to capitalise on the perspective compression inherent in telephoto lenses. While relatively slow at wide apertures, this lens has plenty of potential for stopping down to obtain a wide depth of focus.

      In addition, this lens has some of the closest focusing abilities of any non-macro lens in the RF range. For some photographers, it could replace a separate macro lens when shooting flowers and small animals.

      This lens is virtually free of focus breathing, which is good news for videographers. It also appears to be parfocal, which means there is very little change in focus when zooming in or out.

      Build and Ergonomics
      To keep both weight and price down this lens is mostly made from polycarbonate plastic, although it has a solid metal mounting plate. The front element is approximately 45 mm in diameter and surrounded by an 8 mm wide ring that carries the name of the lens plus Ø67 mm, which denotes the diameter of the filter thread.

      Roughly 15 mm back from the tip of the filter ring is the programmable Control ring, which is 10 mm wide and covered in a stippled texture. Functions like shutter speed or aperture control can be assigned to the control ring, which has click stops to give users a sense of how much it is being turned. (If you want it de-clicked the lens must be returned to the Canon Service Centre.)

      A 5 mm wide band separates the control ring from the focusing ring, which is 25mm wide and entirely covered in fine ridging. Because focusing is controlled by the camera, there’s no direct manual focus override by default; instead it must be activated via the camera’s menu (and even then it remains electronically controlled).

      The zoom ring is located directly behind the focusing ring. It’s approximately 60 mm wide, with a 43 mm wide band of rubberised ridging around its middle and a 5 mm wide unridged strip around the trailing edge, which carries stamped marks to denote the 100mm, 135mm, 200mm, 300mm and 400mm focal length settings.

      This illustration shows the inner barrel fully extended to 400mm, in comparison with the lens set to 100mm. (Source: Canon.)

      These marks line up against a white line on the 35 mm wide fixed section of the lens between the end of the zoom ring and the camera body. Zooming from 100mm to 400mm extends the inner barrel by approximately 75 mm, without rotating the front of the lens. This enables hassle-free use of angle-critical filters.

      The section of the outer barrel between the zoom ring and the camera body contains slider switches for AF/MF focal modes and turning the stabiliser on and off. A zoom lock slider is located around the right hand side of the lens barrel in this section.

      The lens barrel ends in an RF bayonet mount with a small red index line for orientating the lens with the camera body. The chromed metal mounting plate fits firmly to the camera body but there’s no rubber gasket to exclude moisture and dust.

      No lens hood it supplied with this lens, which is a pity as it could probably benefit from one. A large, almost cylindrical ET-74B lens hood is available optionally for between AU$70 and $80.

      We were unable to measure resolution across the entire zoom range using our Imatest system due to a lack of space in our testing area, although we obtained test results from four focal lengths: 100mm, 135mm, 200mm and 259mm. The best performance was recorded at f/6.3 with the 135mm focal length, as shown in the graph of our test results below, although overall performance was consistently good across the range we were able to measure.

      The graph above shows centre resolution to meet expectations for JPEG files between wide open and around f/9 for focal lengths between 100mm and 200mm and fall a little below expectations for measurements made half-way out from the central zone, with a slight further decline towards the edges of the frame. CR3.RAW files converted into 16-bit TIFF format with Adobe Camera Raw delivered even higher resolution, as expected, particularly in the centre of the frame.

      Lateral chromatic aberration remained well down in the ‘negligible’ zone at all focal length settings and we found no evidence of coloured fringing in test shots. In the graph of our test results below, the red line marks the boundary between ‘negligible’ and ‘low’ CA.

      Vignetting was present in shots taken with the widest apertures at all focal length settings, although it was generally at a low level. Rectilinear distortion was also relatively low, as expected for a telephoto lens, with slight pincushion distortion visible across the zoom range.

      Using the EOS R3 for all our test shots enabled us to take advantage of the camera’s sophisticated autofocusing system so it was no real surprise to find autofocusing was fast and accurate for both stills and movies. Hunting only occurred when the lens was required to span a wide distance range and subject conditions were sub-optimal. Even then, the camera and lens combined to achieve sharp focus rapidly, resulting in very few missed shots.

      We found no evidence of focus breathing and no apparent change in focus while zooming between different focal length settings. Autofocusing and zooming were virtually silent, completing the key requirements for a lens that will be used for video recordings.

      In addition, the lens was very easy to use hand-held, even on a relatively heavy camera like the EOS R3. And the combination of the stabilisation in the lens and the IBIS and Movie Digital IS video stabilisation in the camera meant most clips were smooth and sharply focused.
      The close-up capabilities of the lens were impressive, particularly at 300mm and 400mm. Almost half life size reproduction is possible with the 400mm setting and at both focal lengths the lens provided a comfortable working distance for photographing potentially tricky subjects.

      Bokeh at wide apertures was also smooth and attractive, although some highlight outlining was found at shorter focal lengths.  Fortunately, highlights remained mostly circular across the image frame.

      The combination of the image stabilisation in the lens and the IBIS system in the EOS R3 allowed us to shoot with camera and lens hand-held for all of our test shots. Panning shots were generally successful, thanks to the combination of subject recognition and the ability of the IS system to recognise when the camera was being panned and adapt to the motion automatically.

      Poor weather conditions during the period we had the lens for testing limited our ability to fully test backlighting performance. However, under optimal conditions the lens can produce attractive 18-pointed sunstars when stopped down to f/22 or smaller apertures.


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      Picture angle: 24 to 6.17 degrees
      Minimum aperture:  f/32-45
      Lens construction: 12 elements in 9 groups (including 1x UD and 1x aspherical elements), Super Spectra multi-coating
      Lens mounts: Canon RF mount
      Diaphragm Blades: 9 (circular aperture)
      Weather resistance: None
      Focus drive: Nano USM motor
      Stabilisation: Yes; 5.5 stops
      Minimum focus: 88 cm (at 200mm)
      Maximum magnification: 0.41x (at 400mm)
      Filter size: 67 mm
      Dimensions (Diameter x L): 79.5 x 164.7 mm
      Weight: 635 grams
      Standard Accessories: Front and end caps

      Distributor: Canon Australia; 1800 021 167



      Based on JPEG files recorded with the lens on the Canon EOS R3 camera.

      Based on CR3.RAW files recorded simultaneously and converted into 16-bit TIFF format with Adobe Camera Raw.



      Vignetting at 100mm f/5.

      Vignetting at 135mm f/5.

      Vignetting at 200mm f/5.6.

      Vignetting at 300mm f/6.3.

      Vignetting at 400mm f/8.

      Rectilinear distortion at 100mm.

      Rectilinear distortion at 135mm.

      Rectilinear distortion at 200mm.

      Rectilinear distortion at 300mm.

      Rectilinear distortion at 400mm.

      Minimum focus at 100mm, ISO 200, 1/640 second at f/5.6.

      Minimum focus at 135mm, ISO 200, 1/500 second at f/6.3.

      Minimum focus at 200mm, ISO 200, 1/500 second at f/7.1.

      Minimum focus at 300mm, ISO 200, 1/320 second at f/8.

      Minimum focus at 400mm, ISO 200, 1/200 second at f/8.

      Close-up at 100mm focal length, ISO 200, 1/40 second at f/5.6.

      Close-up at 120mm focal length. ISO 200, 1/40 second at f/5.6.

      400mm, ISO 200, 1/500 second at f/8.

      Bird in flight; 300mm focal length, ISO 200, 1/250 second at f/8.

      400mm focal length, ISO 800, 1/6400 second at f/11.

      Crop from the above image magnified to 100% to show actual sharpness and the effectiveness of the bird recognition mode in the R3’s AF system.

      400mm focal length, ISO 800, 1/400 second at f/8.

      Crop from the above image magnified to 100% to show actual sharpness.

      Sunstars at 200mm focal length, ISO 200, 1/4 second at f/36.

      Sunstars at 300mm, ISO 200, 1/20 second at f/45

      Sunstars at 400mm, ISO 200, 1/40 second at f/45.

      300mm focal length, ISO 200, 1/320 second at f/8.

      400mm focal length, ISO 1000, 1/640 second at f/11.

      400mm focal length, ISO 1250, 1/800 second at f/10.

      300mm focal length, ISO 400, 1/640 second at f/8.

      400mm focal length, ISO 640, 1/500 second at f/8.

      Panning shot; 236mm focal length, ISO 500, 1/120 second at f/7.1.

      214mm focal length, ISO 400, 1/250 second at f/7.1.

      165mm focal length, ISO 200, 1/250 second at f/7.1.

      Backlit subjects; 400mm focal length, ISO 200, 1/320 second at f/8.

      135mm focal length, ISO 200, 1/400 second at f/10.

      400mm focal length, ISO 200, 1/400 second at f/8.

      Additional image samples can be found with our review of the Canon EOS R3 camera.



      RRP: AU$1379; US$649

      • Build: 8.7
      • Handling: 8.8
      • Image quality: 8.9
      • Autofocusing: 9.0
      • Versatility: 8.7