Canon RF 28-70mm F2L USM Review

The Canon RF 28-70mm F2L USM is a professional-level lens with the RF mount, which means it’s designed for use on mirrorless cameras like the full-frame Canon EOS R5 and Canon EOS R6, as well as the older EOS R and EOS RP.

A 24-70mm f/2.8 lens is often the go-to standard zoom lens for professional photographers, so the Canon RF 28-70mm F2L USM is rather unusual, starting at a slightly longer focal length but having a stop large aperture. That extra brightness could be helpful in low light conditions or when the background needs a bit more blur, but it makes the lens very bulky.

Inside the Canon RF 28-70mm F2L USM’s weather-sealed barrel there are 19 elements arranged in 13 groups with four aspherical elements and three ultra-low dispersion (UD) elements to maintain detail across the image field and limit distortion.

Canon has also applied its Air-Sphere Coating (ASC) and Subwavelength Structure Coating (SWC) on the surface of some elements with the aim of suppressing flare and ghosting.

Focusing is handled by Canon’s Ultra Sonic Motor (USM) system.

The lens has no stabilisation built-in, but the Canon R5 and R6 both have in-body image stabilisation (IBIS).

Although you can check the specifications and see that the Canon RF 28-70mm F2L USM weighs 1430g and measures 103.8 x 139.8mm, it’s only when you hold it, or compare it to another lens that you realise just how big it is. It’s 530g heavier than the Canon RF 24-70mm F2.8L IS USM, for example, which measures 88.5x 125.7mm. And it’s 360g heavier than the RF 70-200mm F2.8L IS, which measures 89.9 x 146mm.

It also has a 95mm filter thread, which is likely to mean that you need to upgrade your filters.

For comparison, here’s the Canon RF 28-70mm f2L USM alongside the Sigma 28-70mm f2.8 DG DN | Contemporary. The Sigma 28-70mm f2.8 DG DN C is a compact lens that is 1stop slower but is designed to deliver high optical performance that is close to the standard of the company’s Art lenses.

Sigma 28-70mm f2.8 DG DN C vs Canon RF 28-70mm F2L USM

I used the RF 28-70mm F2L USM on the Canon R5, which itself weighs 650g, making the total weight over 2Kg. That is a lot for a ‘standard’ zoom lens set-up, but the word standard doesn’t seem applicable to a zoom lens with a constant aperture of f/2.0.

The RF 28-70mm F2L USM also has three control rings, one for the focal length with markings at the 28, 35, 50 and 70mm points, one further forward for manual focusing and a front ring that can be customised to adjust one of a long list of parameters. I used the control ring to adjust exposure compensation, which is very handy with such a big, heavy lens as it needs a supporting hand and the ring falls within easy reach of your left thumb and forefinger.

It would be nice to see a button on the lens to enable the purpose of the control ring to be switched quickly to control something else, perhaps the aperture setting, but there isn’t.

All three of the dials have a nice action, requiring positive force but no real effort. One disappointment with the control ring is that there’s no de-click control. You can send the lens to Canon to have it de-clicked for a fee, but you can’t use it with clicks for photography and de-clicked for video at will.

As I’ve mentioned, I tested the Canon RF 28-70mm F2L USM on the 45Mp Canon EOS R5 and they make a fine pair, capturing a high level of detail with no major flaws – but you’d expect that at the RF 28-70mm F2L USM’s price.

Curvilinear distortion is kept under control very well, but if you turn the correction profile off in Adobe Camera Raw, you’ll see a slight hint of barrel distortion at the 28mm point. It’s hardly worth mentioning, especially as the profile, which can be applied in-camera or at the processing stage, irons it out.

Sharpness levels are also very good although it’s worth avoiding the smallest aperture setting (f/22) if you can. There’s also a slight loss of sharpness towards the corners of the frame, particularly at the widest end of the lens when the aperture is wide-open, but this isn’t apparent in most real-world photography. Closing down to f/2.8 and f/4 improves the corner sharpness.

Unsurprisingly, the corners are best at the longer focal lengths.

If you hunt for it, you may find the odd example of chromatic aberration along some high contrast edges towards the corners of the frame, but they’re kept under control very well by the correction profile. I spotted a couple of bits of fringing that escaped the impact of the removal profile, but these were dealt with very quickly and easily using the controls in Adobe Camera Raw.

Although there are some large elements inside the RF 28-70mm F2L USM, the focusing is fast and very quiet – but still audible. What’s more apparent than the noise of the focusing, however, is the focus breathing exhibited by the lens. The framing changes subtly when the focus distance alters, which could be an issue for videographers.

Out of focus areas look very nice with circular, clean highlights devoid of aberration and wonderfully smooth even-toned areas.

Follow the link to browse and download full-resolution images shot on the Canon EOS R5 with the RF 28-70mm f2.8L UMS mounted.

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Optically the Canon RF 28-70mm F2L USM is very good, but its weight and size make it cumbersome. It’s a weight that I’d accept from a telephoto zoom lens, but the 28-70mm focal length range is more ‘everyday’ and given the cost of the RF 28-70mm F2L USM, I’d want to be using it constantly. I also missed the wider reach of a 24-70mm lens.

You might argue that the RF 28-70mm F2L USM is lighter and more convenient to use than four f/2.0 lenses, and it’s certainly true that zoom lenses are convenient. But I wouldn’t carry four prime lenses of the combined weight of the RF 28-70mm F2L USM on one shoulder, I’d have three of them in a backpack and one mounted for action.