Canon RF 24- 240mm F4-6.3 IS USM: lens test

The zoom was used at 240mm to capture this silhouette of a photographer on Camber Sands in East Sussex Canon EOS R, 1/400sec at f/6.3, ISO 250

LENS TEST

T estbench

Canon RF 24-240mm F4-6.3 IS USM

All-in-one zooms have their benefi ts. Michael Topham discovers if Canon’s example for its EOS R series is a good one with a gruelling test

It was around this time last year that Canon revealed plans to strengthen its lineup of four lenses that were initially released for the EOS R system by adding six lenses that would arrive over the course of 2019. One of these six was the RF 24-240mm F4-6.3 IS USM –an opticallystabilised 10x superzoom that addresses one concern surrounding the system, namely the unavailability of an all-in-one lens. The benefi t of a zoom like the one we’re looking at in this review is that it covers most bases for trips away when space might be limited or you want to travel light and take only one lens with you. Wide enough to capture stunning landscapes and long enough to pick out sports or wildlife subjects, it’s currently the longest and most versatile zoom Canon has made since entering the mirrorless market. Before analysing its optical performance lets take a closer look at its key features.

Features The RF 24-240mm F4-6.3 IS USM is compatible with Canon’s EOS R and EOS RP full-frame mirrorless cameras. As well as being sold on its own, it’s available as part of a bundle with the EOS RP (£1,649), but not the EOS R. This, combined with the fact it’s not an L-series lens, emphasises that Canon is targeting it at amateurs and enthusiasts who already own, or who are considering, the EOS RP.

For a travel zoom to be successful, size, portability and weight are ultimately key. The RF 24-240mm F4-6.3 IS USM has a thinner barrel than many of the L-series lenses Canon has released into its RF lineup. With a diameter of 80.4mm, a retracted length of 122.5mm and weighing a respectable 750g, it balances nicely and is well proportioned with Canon’s EOS R models for which it’s designed. Internally, the lens features an optical construction that consists of 21 elements in 15 groups, with seven diaphragm blades. To offset handshake and prevent handheld images at telephoto lengths being susceptible to blur, Canon has equipped the lens with a highly effective fi ve-stop image stabiliser –an essential feature given that no available EOS R model at the time of writing features in-body image stabilisation (IBIS). The lens doesn’t benefi t from Canon’s latest electronic fl oating focus control mechanism that we’ve seen recently in the RF 70-200mm F2.8L IS USM, but it still promises fast focusing with its near-silent single Nano Ultrasonic (USM) motor. In contrast to existing RF lenses, which include an additional click-stopped

The lens is prone to fringing along high-contrast edges, but it’s an easy fix in JPEG images by ensuring lens aberration corrections are turned on Canon EOS R, 1/80sec at f/22, ISO 200

control dial, the lens has a dual control ring that can be switched between manual focusing and setting exposure parameters via a selector on the barrel. Other points of interest include its 0.5m minimum focus distance at full telephoto, a variable minimum aperture range of f/22-f/38 and acceptance of screw in fi lters and adapters via a 72mm fi lter thread at the front. The lens comes with front and rear lens caps as you’d expect, however a hood and lens case/ pouch aren’t bundled in the box. These are optional accessories, with the EW-78F hood and the LP1219 case adding £35 and £25 to the price respectively.

Build and handling The lens looks at home paired with Canon’s EOS R cameras. The dark silver surround to the mount blends nicely with the mount of

EOS R models and the matte black barrel has a similar texture and fi nish to the top plate of the EOS RP and EOS R. To prevent the zoom extending inadvertently it has a lock switch that can be engaged at 24mm. Unlike some zoom locks that can be disengaged with a sharp twist of the zoom ring, it does require you to fl ick the switch back again to unlock it. On the opposite side you’ll fi nd the stabiliser switch that has on/off positions. Above it is the focus/control switch that lets you choose whether the diamond knurled control ring is used to focus manually or change a userspecifi ed setting. Enter the customise dials option in the menu and the control ring can be set to adjust aperture, shutter speed, ISO or exposure compensation, either directly, or by holding the metering button if you’d like to avoid accidental or unintentional changes. It

Telephoto 240mm Wideangle 24mm

‘It’ll cover most bases for amateurs and hobbyists’

should be pointed out that the control ring is quite sensitive though and doesn’t need to be rotated far before settings start to change. Despite not having a red ring, which denotes Canon’s professional L-series lenses, the overall build quality is good. The zoom ring is rubberised just as it should be and the plastics used in the construction of the barrel are of high quality. The switches operate positively and the clickless aperture control when shooting movies will be welcomed by videographers. Best of all, the zoom has a short throw through 100 degrees, meaning you can get from 24mm to 240mm, or vice versa, very easily in one quick movement. It offers suffi cient resistance to prevent zoom creep when the camera is pointed down and it’s consistently smooth throughout its zoom range with no change in fl uidity. Extending the lens to its maximum focal length does increase its overall length to 192mm, which is 69.5mm longer than when it’s retracted; however the front of the lens doesn’t rotate, which is good news for those who work with fi lters and don’t want to be forever readjusting them between shots.

Image quality Superzooms have their work cut out when it comes to resolving excellent image quality across their extensive focal ranges. Unlike primes, which are optimised to produce the fi nest optical quality at one particular focal length, a compromise in optical performance usually has to be made choosing an all-in-one lens. Studying real-world

LENS TEST

Testbench

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Canon RF 24-240mm F4-6.3 IS USM

Resolution

Our Image Engineering Tests tell us the lens is sharpest in the centre when it’s used at the wide end of the zoom, with corner sharpness improving as you start to zoom in. The best edge-to-edge sharpness is resolved around 70mm at f/8, with good centre sharpness being maintained at 240mm between f/6.3 and f/11. Sharpness drops off quickly beyond f/11 owing to the introduction of diffraction.

A magnified view of centre sharpness with the zoom set to 160mm Canon EOS R, 1/800sec at f/6.3, ISO 100

images taken with peripheral illumination correction and the digital lens optimiser turned on from the lens aberration correction settings revealed no barrel distortion or vignetting towards the corners in JPEGs captured at 24mm. It’s not the same story for raw fi les though, which are subject to barrel distortion at 24mm, turning to pincushion distortion at longer focal lengths. The image circle doesn’t fully cover the sensor at 24mm either so you get very dark corners at the edges. Thankfully, a lens profi le is available in the latest version of Adobe Camera Raw and Lightroom, which does a fi ne job of correcting this, though you should still expect the corners at wide angle to be soft compared to the centre of the frame, even when stopped down. Reviewing my images also revealed that uncorrected raw fi les are prone to exhibiting green and purple fringing, but this was removed effectively by ticking the Remove Chromatic Aberration box or taking manual control of the defringe sliders. It goes without saying: if you regularly shoot JPEGs you’ll want to double check that all lens aberration corrections are turned on within the camera before you shoot. If you prefer to work with raw fi les, applying a lens profi le during post processing to correct its optical fl aws is a must. The results from real-world testing are consistent with those we recorded in the lab. Though sharpness in the centre at 24mm resolves the highest fi gure, users should note sharpness towards the edge is considerably softer. Zoom in to 70mm and a noticeable improvement in corner sharpness becomes obvious right across the aperture range, with the best edge-to-edge sharpness in the mid point of the zoom range being recorded at f/8. Sharpness does drop off again at the edge when you push to longer telephoto lengths, however sharpness in the centre at 240mm at its maximum aperture of f/6.3 is impressive. Overall, my lasting impression is that sharpness holds up rather better at telephoto lengths than other 10x zooms I’ve tested.

Verdict

CANON was lacking an all-in-one lens for its EOS R system and it has delivered a respectable example with the RF 24- 240mm F4-6.3 IS USM. It’s not optically perfect and you do need to be prepared to make some compromises when it comes to the sharpness that’s resolved in the corners. As is often the case with superzooms, it’s not immune from curvilinear distortion, vignetting or chromatic aberration either, however these optical fl aws are brilliantly corrected for in-camera and can be remedied easily in raw fi les by applying the relevant lens profi le. It’ll cover most bases for amateurs and hobbyists who are looking for one lens to do it all, or like the idea of travelling light. Its image stabilisation suppresses handshake commendably, it focuses quickly, and provides good control of manual focus or exposure variables from the same control ring. Having a hood supplied in the box would have been the icing on the cake. Price £845 Filter diameter 72mm Lens elements 21 Groups 15 Maximum aperture f/4-6.3 Minimum aperture f/22-f/38 Minimum focus 50cm Dimensions 80.4x122.5mm Weight 750g Lens mount Canon RF Included accessories Lens cap, rear cap Data file

24mm centre 70mm centre 240mm centre 24mm corner 70mm corner 240mm corner

Shading

Users shooting in the JPEG format can correct for corner shading in-camera by enabling the peripheral illumination setting within the lens aberration correction settings from the camera’s menu. Raw files benefit from having a lens profile applied to remove corner shading automatically.

24mm f/4 240mm f/6.3

Curvilinear distortion

With the digital lens optimiser turned on, curvilinear distortion is effectively dealt with and removed in JPEG images. Shooting in raw and inspecting uncorrected images reveals that the lens exhibits severe barrel distortion at 24mm that quickly turns to pincushion distortion.

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