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.
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Expert view: should you make the switch to an RF lens?
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.
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.
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.
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.
Expert view: switching to full-frame
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.
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.
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.