In case you haven’t noticed Canon has a whole new camera lineup out for mirrorless and they called it the RF mount. Unlike the EF mount, RF mount is designed specifically for mirrorless digital cameras. EF mount was designed in the days of film SLR’s. Later in EF mount history it continued on as Canon’s choice for DSLR’s as well. That continuity in the industry’s transition from film to digital and the more modern design and philosophy of EF mount at the time it was introduced ended up being the #1 power play amongst all camera companies at the time. EF mount was able to transition seamlessly to digital and it exploded with the rise of digital photography and Canon became the #1 camera company in the world.
With that kind of success behind a product it’s no wonder Canon has seemed hesitant to ditch EF mount altogether. EF mount is a very modern design and it has proved capable of pushing camera technology to a high level.
The word of the moment in photography is “mirrorless”. And it’s no wonder really, the mirrorless cameras have eliminated a lot of the complexity in cameras and generally made them better in almost every possible way.
So it is then that Canon pretty much had to switch to mirrorless, the market was shifting hard in that direction and for good reason. Mirrorless has a number of intrinsic advantages that while not impossible to achieve in a DSLR would double or triple the cost of the system in a DSLR.
One of the miracles of technology is that it can do pretty much anything we can think of. But the question we have to ask is, just because you can, does it mean you should?
From a reliability standpoint it is hard to fault a mirrorless camera. It’s about as simple as a device can get. No more flappy mirror, and in some cases, no more shutter either. If you look at the internals of a modern mirrorless camera they’re actually not that complex. Sure the computer chips look super complicated but the fact is they’re really not that complicated either.
The big advantage of mirrorless is that the mirrorless cameras make it easy for the camera to see the image the same way we see the image. In a mirrorless camera the sensor is also the shutter, it is the mirror, and it is the focusing sensor as well.
While in theory a DSLR can focus as well as a mirrorless camera can, the fact is that as of right now in order for a DSLR to do that it is basically working as a mirrorless camera. With that in mind you have to ask what is the point of the mirror if you’re not even using it?
And that is the approach that RF mount takes. RF mount answers the question by saying there is no point to the mirror! The mirror adds a lot of technology and expense without adding a lot of benefit. The big advantage of shooting in mirrorless mode is that the camera can show the photographer what their current exposure looks like. Mirrors are not able to do that right now.
Another big advantage of mirrorless is that it makes getting *exact* exposures a walk in the park. Since the sensor is fully exposed to the scene as you frame your picture the camera can tell you with near perfect precision if even a single pixel is overexposed.
And, since the sensor is fully exposed to the scene the entire time you are framing the shot the sensor can now perform a variety of other computations that allow the camera to track objects on the screen and adjust exposure and focus accordingly if necessary.
Ultimately, mirrors were needed for film, and they are not needed for digital. The purest form of a digital camera is a mirrorless camera.
Technical Advantages of RF mount
RF mount has a number of technical advantages. One of the more obvious is how many communication pins it has to connect to the body with. RF mount has 12 pins vs EF mount’s 8 pins. Think of that like adding more lanes to a highway. The increased number of pins increases power and bandwidth possibilities for lens-body communications. For instance, many if not all RF mount lenses have motion sensors mounted within them regardless of whether they contain stabilization elements in the lens. That is a difference from older EF lenses many of which don’t have motion sensors in them. RF mount lenses include these sensors to better communicate camera position and movement for camera bodies that have IBIS. The extra pins provide dedicated channels for power & data to serve all the different systems such as the more elaborate stabilization electronics that are now present in modern lenses.
The updated mount also allows the camera body and the lens to synchronize their stabilization when a stabilized lens and body are used together. This results in an overall stabilization effect that is better than IBIS alone or lens IS alone. Now it is possible for the two systems to work together. All the RF lenses that have IS in them will achieve 6.5 stops or greater stabilization when used with a camera body that has IBIS in it. The new R3 promises to increase that by a full stop as well, so be prepared to see an even greater stabilization effect here.
On RF mount the speed of the electronics in the lens and body has also been updated enabling things like the AF to operate faster. The improved AF communication between lens and body allows the Dual Nano USM lenses like the RF 70-200mm f/2.8 to focus really fast.
Other advantages of the RF mount go beyond the electronics to the physical design of the mount.
I am not a lens designer so I can’t confirm this but the word on the street is that due to the reduced back-focus distance RF mount wide angle lenses are easier to design than their EF mount equivalents. This should enable even wider and better corrected rectilinear lenses such as the RF 15-35mm f/2.8.
And even though the actual lens mount is the same size as EF the effective size is increased because it is moved closer to the sensor. This allows for a very large entrance pupil (aperture) to be designed into the lens. In fact there is speculation that a RF 60mm f/1.0 may be in the works! How exciting is that?
There is a lot to be excited about on RF mount from a technical perspective.
Pros and Cons of each mount
There are no pro’s to the EF mount, the RF mount is superior in every way possible except for purists who enjoy looking through a prism and at a mirror to see through the lens. In reality, this is a detraction because it is less accurate, less truthful, and far less flexible than an Electronic Viewfinder.
The pro’s to RF mount are numerous and the first thing to note is that the camera is simpler and less costly to manufacture. There are fewer moving parts and things to break over time or require service. Therefore the cameras will also be longer lasting and more durable.
Of course they could in theory make a mirrorless EF mount camera with no mirror or pentaprism. They could instead employ an EVF as the RF mount cameras do. However, this arrangement would not take advantage of the ability of RF mount cameras to be slightly more compact. Additionally, as mentioned above, the reduced back-focus distance allows for new lens designs that may have been too costly to attempt with the EF mount.
Another big advantage of RF mount for me personally is that reducing the back focus distance makes room outside the camera for the use of lens adapters. This basically lets you use any of the old SLR lenses from the days of film on an RF mount camera exactly as they are intended to be used. You can use anything you want, Medium Format lenses, Hasselblad lenses, Contax lenses or even Canon FD lenses. In fact I have a number of old Canon FL lenses that I use on my RF mount cameras.
This plays into another pro for RF mount, it is fully compatible with ALL EF mount lenses. It is also compatible with any other brand of autofocus lenses if an adapter has been made for the lens. Yep, that means you can use old Nikon DSLR lenses too exactly as if they were made for a Canon camera.
If you are wondering if there are adapters to use some of these lenses on EF mount, the answer is that yes, there are, but there are caveats to that. Because there is no room for the extra space of the adapter on EF mount an adapted lens is further from the sensor plane than it should be, this means it is essentially working as if on a Macro Extension tube, which means the loss of infinity focus. In order to compensate for that some adapters include an optic which corrects for the extra distance but usually lowers the quality of the image and can induce effects and behaviors in the optic that shouldn’t be there. It also means that designing an adapter for EF mount is more costly and requires a lot of expertise that most adapter companies don’t really have. Finally, just as with teleconverters, an adapter that uses an optical corrective element may work great on some lenses and terribly on others.
Ultimately RF mount is superior when it comes to adapting old SLR lenses to digital, it is actually perfect for that so another huge pro in favor of RF mount and a con for EF mount.
There are still people who stubbornly insist that the optical viewfinder is better, well, it isn’t. The EVF in my experience is superior in every way and even makes manual focusing 10 times easier. It is just bigger, and brighter, and easier to see the details than any optical viewfinder will ever be. How is that a bad thing?
Sure they could have just taken the mirror out of the EF mount but then it wouldn’t be a true digital mount. As mentioned above, the removal of the extra space in the EF mount allows for the use of millions of old lenses on modern RF mount cameras. I think that makes RF mount a lot more interesting for photographers who are interested in old gear and how it worked and what kind of unique looks it can provide today. It also makes getting into photography a lot cheaper. Now you can buy an old lens to go with your RF mount camera and maybe get some pictures you would not have gotten without it.
In conclusion, RF mount is better than EF mount because it is a pure digital mount. RF mount was made for a digital age whereas EF mount was designed for analog film. RF mount is the future.