ARTICLE

Expert view: should you make the switch to an RF lens?

Continuing our series of technical explainers by Canon experts, product specialist Mike Burnhill outlines some of the benefits of switching from an EF lens to its RF counterpart.
Canon's three professional f/2.8 RF lenses: RF 15-35MM F2.8L IS USM, RF 24-70MM F2.8L IS USM and RF 70-200mm F2.8L IS USM.

Canon's "trinity" of f/2.8 RF lenses covers ultra-wide, standard and telephoto zoom ranges, for shooting in practically any situation from landscapes, portraits and sports, to interiors, fashion and cityscapes.

There are a lot of big questions in photography, as in life. In our previous Expert View article, my colleague John Maurice answered one of these, about full-frame vs APS-C cameras. Here I'll tackle another of the most common questions people ask us: should I switch from my beloved EF lens to its RF counterpart?

If you are asking this question, then you might already have decided on one of Canon's EOS R System cameras, which are built around the groundbreaking RF lens mount but can also use EF and EF-S lenses, with no loss of quality or functionality, thanks to a range of EF-EOS R mount adapters. Alternatively, you might be asking because your decision depends on how the RF lenses perform compared to their EF predecessors.
Mike Burnhill, Senior Product Specialist at Canon Europe.
Mike Burnhill is Senior Product Specialist at Canon Europe. He has worked for many of the UK's biggest photo dealers and as a forensic photographer for the Metropolitan Police. He has looked after Canon's pro cameras and lenses since 2012, and has supported pro photographers with the Canon Professional Services team at many of the biggest sporting events around the globe.
So before discussing specific lenses, it's worth outlining the core benefits that the RF mount offered to Canon's lens designers. Thanks to the wide diameter of the RF lens mount and the short back focus distance between mount and sensor, the lens designers gained three ways in which they could make RF lenses surpass EF lenses:
  • Make lenses more compact while retaining the quality of EF lenses.
  • Make lenses a similar size to EF lenses but with extra performance and added features.
  • Make new types of lenses that were not possible before.
All three of these can be seen in the designs throughout the RF lens range. The reality is, RF lenses deliver innovative features and technological advancements that take them to the next level.
A cutaway illustration of a Canon EOS R System camera with RF 24-105mm f-4L IS USM lens.

Canon's groundbreaking RF lens mount makes it possible for Canon's lens developers to create a new generation of lenses using cutting-edge optical designs to enhance optical performance and deliver more functionality than their EF counterparts.

The most obvious addition to all RF lenses is the control ring. This customisable function ring can be used to adjust various camera settings directly, including aperture, ISO, shutter speed and even white balance or changing the AF area. Combined with other physical controls on the camera, this enables you to adjust key settings quickly and easily without needing to delve into menus.

A second core enhancement in all RF lenses is the aperture mechanism or electromagnetic diaphragm (EMD). In RF lenses the EMD speed has been increased to enable high frame rates, and the EMD is also able to move in smaller increments of 1/8 stop, as compared to the 1/3 stop increments in earlier lenses. This allows hybrid shooters and filmmakers to control the aperture while capturing video without the footage being affected by sudden changes or jumps in brightness.
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These benefits apply to all RF lenses. In addition, if you compare some of our RF lenses to their EF counterparts, you'll discover key differences that set them apart. Let's look at some of these in detail.
A fountain pen rests on a leather-covered book with sea shells alongside and another, open book and two white chess pieces out of focus in the background.

Photographers love the image quality and natural perspective of Canon's 35mm wide-angle EF lenses. Taken on a Canon EOS R with a Canon EF 35mm f/2 IS USM lens at 1/125 sec, f/2 and ISO100.

A closer view of a fountain pen resting on a leather-covered book, with a couple of sea shells alongside and the rest of the image out of focus.

In addition to a wide angle view with a natural perspective, Canon's 35mm RF lens offers macro capabilities, plus powerful Dual Sensing IS technology for superb sharpness when you're shooting handheld. Taken on a Canon EOS R with a Canon RF 35mm F1.8 MACRO IS STM lens at 1/125 sec, f/2 and ISO100.

RF vs EF lenses: fast-aperture 35mm lenses

Let's compare the Canon RF 35mm F1.8 Macro IS STM lens with the EF 35mm f/1.4L IS II USM. This might sound like an unfair comparison, since the EF lens is an L-series lens with a faster aperture and weather sealed design, but the RF version has some tricks up its sleeve that make it a serious lens to consider. With a built-in 5-stop Image Stabilizer and half-life-size macro function, at half the weight and 60% of the size of the EF lens, the RF lens has many benefits to offset the EF lens's advantage of an additional 2/3 of a stop in brightness. Of course, the RF lens does have one major advantage that will appeal to anyone looking at these two lenses: a considerably lower price.
A view from an elevated position of Huis Ten Bosch in Nagasaki, Japan, which recreates a Dutch town with canals.

50mm lenses give a perspective similar to that of the human eye, and the affordable, compact Canon EF 50mm f/1.8 STM is a great choice to take on the road to capture quality images of what you see. Taken on a Canon EOS R5 with a Canon EF 50mm f/1.8 STM lens at 1/2700 sec, f/1.8 and ISO100.

A close-up of a view of Huis Ten Bosch in Nagasaki, Japan, alongside an almost identical image with sharper detail resolution.

The RF 50mm F1.8 STM lens corrects some optical aberrations from which the EF lens suffered (including subtle barrelling) and produces greater edge to edge image quality – compare the detail resolution in this corner of the image (left) alongside the same view taken on the same camera with the RF lens (right). Taken on a Canon EOS R5 with a Canon RF 50mm F1.8 STM lens at 1/2700 sec, f/1.8 and ISO100.

RF vs EF lenses: 50mm lenses

The 50mm lens has been the standard lens for over a century thanks to its natural perspective and magnification. It also generally offers the double benefits of excellent optical performance and fast aperture – and in the case of the EF 50mm f/1.8 STM lens, a reasonable price. So let's start there with the f/1.8 version. These lenses are often the gateway lenses to elevate your photography to another level due to their quality and the control they give you over depth of field. The EF 50mm f/1.8 STM lens in various forms has existed since the dawn of the EOS system, so the optical deign has been refined over decades to produce compact, high-performance lenses at a low cost.
For the RF version the Canon designers faced the challenge that users want a 50mm RF lens to be a similar size to the existing EF lenses. But with the short flange back, a standard optical design would result in a lens that was larger. A redesigned optical formula was needed. So, Canon engineers set to work and created the RF 50mm F1.8 STM lens, which is only 1mm longer than the EF 50mm f/1.8 STM lens.

Designing the RF lens also provided opportunities to combat optical aberrations, by including a newly designed PMO (plastic moulded) aspherical lens element that improved the image quality edge to edge compared to the EF counterpart. Coupled with the previously mentioned RF lens benefits and closer focusing distance, this means the RF lens is worth upgrading to.
The interior of a flooded cave with thousands of stalactites illuminated by blue lights.

Expert view: switching to full-frame

Product Marketing Manager John Maurice on the questions you should ask yourself when considering the move to a full-frame camera system.
A detail from a shot of a young woman leaning out of a window and looking to one side.

The Canon EF 50mm f/1.2 USM lens is renowned for its fast aperture, attractive background blur and L-series optical quality, with lens technologies such as Super Spectra coatings, which ensure accurate colour balance, enhance contrast and reduce flare and ghosting. Taken on a Canon EOS R with a Canon EF 50mm f/1.2L USM lens at 1/2000 sec, f/1.2 and ISO100.

A detail from a sharper but otherwise almost identical shot of a young woman leaning out of a window and looking to one side.

The RF counterpart of the lens incorporates cutting-edge optical technologies and a 10 blade aperture (compared to EF lens's 8) for even smoother bokeh. As is evident particularly around the eyes in this detail from a shot taken with the same camera using identical settings, the RF lens delivers appreciably greater resolution. Taken on a Canon EOS R with a Canon RF 50mm F1.2L USM lens at 1/2000 sec, f/1.2 and ISO100.

RF vs EF lenses: fast-aperture 50mm lenses

When it comes to faster 50mm lenses, the EF 50mm f/1.2L USM has been the benchmark for fast-aperture lenses for over a decade, and a favourite among photographers from photojournalists to wedding photographers the world over. With the lens held in such high regard, it's no coincidence that one of the first RF lenses was the RF 50mm F1.2L USM. For this lens, the Canon engineers set about producing the highest performance lens they had made yet. It includes a UD element, two ground glass aspherical elements and one glass moulded aspherical element, and nearly twice as many elements as the EF lens (15 compared to 8). The RF lens offers stunning performance even when wide open. In addition, it delivers closer focusing, faster focusing speeds, and better ghosting and flare protection than its predecessor, and the result is higher performance in all areas. The improvement in resolution of the RF lens feels like extra resolution has been added to your camera, and it will convince everyone who tries it.
A cutaway view of the Canon EF 24-70mm f/2.8L II USM lens.

The Canon EF 24-70mm f/2.8L II USM lens incorporates three aspherical elements to provide exceptional image quality. Significant reduction in chromatic aberration and reduced colour blur means less time in post production, with an edge-to-edge sharpness usually found only in prime lenses.

A cutaway view of the Canon RF 24-70mm F2.8L IS USM lens.

The Canon RF 24-70mm F2.8L IS USM lens adds next-generation lens technologies including three glass moulded aspherical and three UD lens elements, advanced optical coatings and 5-stop optical IS, as well as Nano USM focusing technology for even more rapid, accurate, smooth and silent focusing.

RF vs EF lenses: 24-70mm zoom lenses

I mentioned that one of the design options for the RF lens designers was to make a lens similar in size to EF lenses but with extra performance. Well, the RF 24-70MM F2.8L IS USM illustrates this perfectly. The EF version, the EF 24-70mm f/2.8L IS II USM, broke the perception that zooms were not as good as primes. So how do you improve on such a lens? How about improving everything! Canon engineers set about creating the perfect pro standard lens for the RF range, a lens ideal for stills, video and hybrid shooters. Nano USM focus motors were used, providing smooth, fast, silent and closer focusing with reduced focus breathing – all perfect for video usage. The image quality was further improved through the zoom range, and to complete the package a 5-stop IS system was squeezed in too. The RF 24-70mm F2.8L IS USM redefines what a professional zoom is in the 2020s.
A Canon EOS 5D Mark IV with EF 70-200mm f/2.8L IS III USM lens alongside an EOS R with RF 70-200mm F2.8L IS USM lens.

From a workhorse to... well, a work pony? The Canon RF 70-200mm F2.8L IS USM lens paired with an EOS R (right) is markedly shorter and lighter than its EF counterpart, the EF 70-200mm f/2.8L IS III USM paired with an EOS 5D Mark IV (left).

Cutaway views of a Canon EF 70-200mm f/2.8L IS III USM lens and an RF 70-200mm F2.8L IS USM lens.

A direct comparison of Canon's EF and RF 70-200mm f/2.8 lenses. The developers of the RF 70-200mm F2.8L IS USM lens incorporated innovative technologies and cutting-edge design to ensure it is not just an RF-mount equivalent of the EF lens but a shorter, lighter, super-compact high-speed telephoto lens for a new generation of photography.

RF vs EF lenses: 70-200mm zoom lenses

If one lens can be described as the professional's workhorse, it's the EF 70-200mm f/2.8L IS USM series of lenses. These appear in an astonishing number of photographers' kit bags. Again, this was a lens that Canon knew was essential to re-imagine for the RF mount. But how to make it new, different, better? Yes, image quality was a factor, obviously, but what other concerns had not been addressed in the various incarnations of the EF lens? Answer: size and weight. What about making it a similar size to the other two f/2.8 lenses in Canon's "trinity" of professional RF zoom lenses? And, while we're at it, why not include faster and quieter focusing, closer focusing distance, better IS and reduced focus breathing? As a result, the RF 70-200mm F2.8L IS USM is approximately 25% shorter and 33% lighter than the EF 70-200mm f/2.8L IS III USM lens, making it the smallest lens of its kind ever built while improving the image quality and just about everything else.

The final word

Canon spent decades building the EF range of lenses, and it's testament to their advanced design that, 30 years after the introduction of the EF system, so many of those lenses are still being used. But it's a very different world to when the EF mount was created. Imaging has changed. Canon looked at the lens requirements needed not just for today but also for tomorrow, and employed innovative technologies and cutting-edge optical engineering to create new, more powerful versions of lenses to provide more possibilities when you're shooting stills but just as importantly video. Canon is creating a series of lenses that can do more, so you can do more.

Skrivet av Mike Burnhill


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