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Canon RF100-400mm F5.6-8 IS USM

Photo: TheFredST / Wikimedia Commons · CC BY-SA 4.0 · source

Lenses

Canon RF100-400mm F5.6-8 IS USM

Canon · Mid-range

A compact RF-mount 100-400mm telephoto zoom for trains photographed from a platform end or a public lineside vantage point.

Expert pick · Digital Camera World, Nov 2021

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We have not tested it ourselves: strengths and weaknesses below come from the tests cited.

Why Railfans Carry It

Trains run along a fixed line, so a long zoom lets you frame a locomotive far down a straight stretch, then widen the view as it closes in. At 400mm the lens reaches well beyond a standard kit zoom, and at about 635 g it stays light enough to carry through a long day on a platform or footbridge. Digital Camera World compares the handling to a classic 70-300mm lens on an APS-C camera, a fair description of how little it intrudes in a camera bag.

In the Field

The reviewers shot it handheld on an EOS R6 and report that the optical stabilizer lives up to Canon's 5.5-stop claim, with Nano USM autofocus described as rapid and sure-footed on moving targets, especially on EOS R5, R6 and later bodies. The lens is also light enough to sit on a tripod without a mounting ring. The aperture is the practical limit: f/8 at 400mm means that in dull light a fast shutter speed needs a high ISO, and one of the 400mm sample frames, taken at 1/1000 s, used ISO 10,000. Lab charts showed very good centre sharpness but noticeably softer corners at every focal length and aperture, and lateral chromatic aberration visible from 200mm upward with in-camera corrections switched off. Sharpness also falls when close focus is combined with the longest zoom setting, which matters little for trains at a distance.

Strengths and Weaknesses

Expert pick · Digital Camera World: Digital Camera World found a compact, light super-telephoto zoom with fast autofocus, effective stabilization and impressive image quality, trading away a slow f/8 aperture at 400mm and weather sealing. Read the review

Strengths

  • Compact and light at about 635 g
  • 5.5-stop optical stabilizer, 6 stops on bodies with in-body stabilization
  • Fast, near-silent Nano USM autofocus
  • Close focusing for a telephoto zoom: 0.41x maximum magnification at 400mm
  • Works with Canon RF 1.4x and 2x extenders

Weaknesses

  • Slow f/5.6-8 aperture
  • No weather sealing
  • Corners noticeably softer in lab tests
  • Lens hood is a separate purchase

Key Specifications

Canon RF100-400mm F5.6-8 IS USM — key specifications
SpecificationValue
MountCanon RF
WeightApprox. 635 g
DimensionsApprox. 79.5 x 164.7 mm (diameter x length)
Focal length100-400mm
Filter diameter67 mm
Maximum aperturef/5.6-8
Image stabilizationUp to 5.5 stops (up to 6.0 with EOS R5)
Maximum magnification0.41x
Minimum focus distance1.2 m at 100mm, 0.88 m at 200mm, 1.05 m at 400mm

Who It’s For

This lens suits railfans with an EOS R-series body who want real reach without a heavy white lens. It is designed for full-frame RF bodies; it also mounts on RF-S APS-C bodies such as the EOS R7, where the view is narrower, but it does not mount on EF or EF-S DSLRs. Look elsewhere if you shoot in rain often, since there are no weather seals, or if you need f/5.6 at the long end for dim winter light.

Alternatives

The Canon RF-S55-210mm F5-7.1 IS STM is smaller and lighter but made for APS-C bodies (on a full-frame body Canon lists it as usable with an automatic APS-C crop). The Canon RF100-500mm F4.5-7.1 L IS USM adds L-series construction, 500mm and a brighter aperture at the long end, in a much heavier and costlier package.

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