Canon RF 24-240mm f4-6.3 zoom lens user review 24 April 2020

Superzoom  lenses have long been popular with travellers and any one who hates changing lenses.

I can't help wondering though......does anyone actually likechanging lenses ?

The greatest zoom range and all round capability can be found in the better bridge cameras. In particular the Sony RX10.4 and Panasonic Lumix FZ1000.2 provide great zoom range, excellent image quality and great versatility in a compact, modestly priced package.

But interchangeable lens systems have also offered long zooms for many years, with aftermarket suppliers like Tamron leading the trend to compact models with a long zoom range at a reasonable price.

The Micro Four Thirds (MFT) system offers several options from Panasonic and Olympus.

APSC cameras have also offered several options from original and aftermarket suppliers over the years.

As sensor size increases so does the challenge of making a consumer friendly superzoom optic.

Sony introduced a 24-240mm travel zoom for its full frame FE system in 2015.

Canon introduced the EF  28-300mm L lens in 2004. This is still available so I guess it has found favour with professionals. But it is a big,  heavy, expensive  thing unlikely to attract enthusiast amateur buyers.

Enter the RF 24-240mm f4-6.3 which is very similar to and no doubt intended to compete with the Sony  FE 24-240mm.

As the Canon RF system develops we can see three tiers of lenses emerging.

At the very top we find a few “hero” models presumably introduced to proclaim Canon’s ability to deliver the highest possible quality in consumer lenses.

These include the 28-70mm f2, 50mm f1.2 and 85mm f1.2.

Next in the top tier there are professional optics such as the 15-35, 24-70 and 70-200mm constant f2.8 zooms.

In the middle tier are the enthusiast/amateur models. Some of these carry the “L” designation, with or without which they are perfectly suitable for professional use.

These include the 35mm f1.8 and the 24-105mm f4 L.  I have both these lenses and find them optically and mechanically excellent.

In the third tier we find what I call utility zooms. These are for buyers who want to have access to a 43mm sensor (full frame) system without breaking the bank.

Here we find the RF 24-240mm and the now-delayed-by-Covid19-but-soon-to-be-available-I-hope RF 24-105mm f4-7.1.

The main appeal of the RF 24-240mm lens is that it manages to combine 10x superzoom capability, moderate dimensions,  moderate price and an entry into the evolving RF system.

No doubt Canon would like to entice users into the RF system with one of the utility zooms then upsell them to the next tier in due course.    

So how does the RF 24-240mm perform ?

Mechanically it is very nice. The zoom action is very smooth. Autofocus is fast and precise on the R and the stabiliser works very well.

Filter size is 72mm.

There is only one ring on the lens besides the zoom ring. This is smoothy not clicky.

It does dual duty for manual focus or control via a slider switch on the side of the lens barrel.

Unfortunately there is no AF/MF switch on the lens so switching from AF to MF involves a trip to a menu as that option is not available on the Q Menu or the Fn button.

I put AF/MF on My Menu for reasonably easy access.

The lens is not weather sealed.

I wish Canon would include the lens hood with its utility zooms. The lens cost me $1120 retail in Australia on one of the increasingly frequent specials which are a feature of the market right now. 

The price today is $1459.

I would be surprised if the hood cost more than two bucks to make. My guess is that they don’t include the hood to differentiate the utility lenses from the L designated ones.

I shot a thousand + frames of static subjects and action including running dogs, birds in flight, moving cars and moving people. 

For optical testing I compared the RF24-240 with two bridge cams, the Lumix FZ1000.2 and Sony RX10.4 and also the Canon RF 24-105mm L with both Canon lenses on the EOS R.

Whereas the RF24-105mm f4 delivers very good results at all focal lengths and apertures right across the frame, the RF24-240mm is less even, being very good at some focal lengths but not so good at others.

In the range of about 35-150mm focal length the RF24-240mm delivers very good to excellent sharpness across the frame right from the widest available aperture.

At 50mm f5 and 100mm f5.6  the 24-240 matches the 24-105 f4 for sharpness across the frame.

There is moderate distortion, color fringing and  peripheral shading.

These issues are largely corrected by applying a dedicated lens profile.

At the wide end of the zoom there is extreme barrel distortion in RAW files with strong peripheral shading and color fringing and moderate loss of sharpness.   Most of the distortion, color fringing and shading are corrected by

a) Using JPG capture or

b) Applying profile corrections in Adobe Camera Raw or Lightroom or Canon DPP.

It may in addition be necessary to apply manual corrections for color fringing in an image editor such as Adobe Camera Raw, depending on the subject.

At the long end, as we zoom from 150mm to 240mm,  good central sharpness continues but the periphery is strongly affected by shading, color fringing and loss of sharpness.

Shading and color fringing are partly corrected with the lens profile but in my tests I had to use manual corrections in addition on most shots.

I found that peripheral sharpness is quite good on my test chart which is 120x80 cm in size, with the camera about 8 meters from the chart.

But with subjects at greater distance, around 25 meters or more, I found peripheral sharpness much lower.

At these subject distances and a focal length equivalent to 240mm, the bridge cameras easily outperform the RF24-240mm in the periphery of the frame, even though their sensors are much smaller and their pixel count lower.

Closing down the lens aperture does not improve peripheral sharpness at the long end of the zoom.

Resistance to flare appears quite good. Bright subject elements in the frame can flare but the lens copes quite well with the sun in or just outside the frame.

The RF 24-240mm is a difficult lens to review because it presents the user with some desirable features but these come bundled with significant defects.

I see this as a good quality 35-150mm lens which has been stretched at the wide and long ends with heavy reliance on post capture profile corrections to reach the magic 10x zoom ratio. 

The problem is that while software solutions are useful for correcting  distortion, peripheral shading and some types of color fringing they cannot rectify the inability of a lens to render fine details.

Some contributors to user forums have indicated they are happy with this lens which meets their imaging requirements.

Desirable features:  Usefully compact for a 10x zoom on the 43mm sensor size, good handling, fast focus, good stabiliser, good sharpness in the frame center at all focal lengths and across the whole frame in the middle of the focal length range.

Undesirable features: There is really only one intractably undesirable feature.

That is loss of peripheral sharpness at the wide and long ends of the zoom range.

This is partly correctable at the wide end by closing down the lens aperture but that strategy is not effective at the long end.

The peripheral shading and color fringing are mostly correctable in a good photo editor.

I can recommend this lens for its versatility and all-in-one convenience provided the buyer is aware of its weaknesses and is able to

a) rectify things which can be largely corrected in an imaging editor (distortion, peripheral shading, color fringing)  and

b) live with the residual issues, which may or may not be a problem depending on the type of photography practiced and the user’s requirement for sharpness at the edges of the frame.