The Canon RF 50mm f/1.8 STM (Amazon, B&H) is primarily a photography lens, though it will be used for video.
In this article let’s take a comprehensive look at the important features and specifications of the Canon RF 50mm f/1.8 STM and see how good it will perform specifically for video, cinematography and filmmaking.
The aim of this article is to provide you with enough information and perspective so you can decide for yourself whether this lens is right for your film or video.
Important: This article is a comprehensive overview of the lens with available information; and an analysis based on our experience shooting for almost two decades. It is not a hands-on review. If and when we get hold of the lens we’ll be sure to publish a detailed review. If this is not your cup of tea you can stop reading.
Here’s Canon’s official video for the 50mm f/1.8 STM:
Click to what you want quickly:
- TLDR;
- EF vs RF:
- Features:
- Control:
- Basics:
- Alternatives to the RF 50mm f/1.8 STM
TLDR;
What you need to know for video work about the Canon RF 50mm f/1.8 STM (Amazon, B&H):
- The Canon RF 50mm f/1.8 STM is a great general purpose focal length. Many would consider this how “the human eye sees”. This lens should work great in low light.
- The f/1.8 aperture is great for low light work.
- Focus ring can be changed to fly-by-wire for follow focus work.
- Control ring can be de-clicked for a small fee at a Canon service center for aperture transitions.
- The lens doesn’t have Image Stabilization, but you will get some stabilization with a Canon R camera (R5, R6, etc.) that has IBIS.
- Great dual pixel autofocus for video.
- It exhibits breathing.
Can be great for the following types of filmmaking:
- Wedding filmmaking
- Documentary filmmaking
- Low budget music videos
- Gimbal use
- Corporate videos and low budget commercials
EF vs RF: What’s the difference?
Difference between the RF and EF mount
Both are lens mounts specific to Canon. Let’s take a look at some important distinctions.
Flange focal distance
The RF is a new lens mount, with a smaller flange focal distance.
Here’s how the flange focal distance compares:
| Mount | Flange Focal Distance |
|---|---|
| RF | 20mm |
| EF | 44mm |
EF lenses were designed for DSLRs. Now with the mirror gone, that’s space and weight savings. However, that’s not the only advantage.
Canon (and every one else) maintains the smaller flange focal distance allows for larger apertures (for some focal lengths), better corner to corner sharpness and reduced light fall off.
Ergonomics
RF lenses are supposed to be lighter, making them easier to handle for photography, but slightly problematic for video. Weight gives better stability and smoother movement for most use cases. For gimbal, drone and steadicam use, the lower weight is an advantage because a lighter lens puts less strain on motors, and the human arms that have to hold it up.
The RF mount is equipped with 12 communicator pins compared to 8 pin connection of the EF mount. Canon claims this contributes towards quicker autofocus, better AF tracking and improved image stabilization.
Canon has redesigned the focus actuators for a hassle-free filming. They claim the new Nano USM and Dual Nano USM have been designed for video. Canon claims that the introduction of these actuators in RF lenses will result in a quieter and quicker autofocus.
The last major change is in the optics. Canon have redesigned the optics from the ground up to account for the smaller flange focal distance. This one simple change considerably changes the optical characteristics and challenges.
Naturally the prices of RF lenses match the high quality Canon have put into these series! The assurance is, the quality isn’t compromised, and with proper care Canon RF lenses should last for years. Let’s compare the EF version of the 50mm with its newer RF counterpart.
Canon EF 50mm f/1.8 STM vs Canon RF 50mm f/1.8 STM
| Lens | RF 50mm f/1.8 STM | EF 50mm f/1.8 STM |
| Filter Thread | 45mm | 49mm |
| Size | 69.2mm x 40.5mm | 69.2mm x 39.3mm |
| Weight | 160g | 160g |
| Lens Control | Ring control | none |
| Closest focusing distance | 0.3m / 0.98 ft | 0.35m / 1.14 ft |
| Max. Aperture | f/1.8 | f/1.8 |
| Min. Aperture | f/22 | f/22 |
| Aperture Blades | 7 blades | 7 blades |
| Angle of View (Diagonal) | 46° | 46° |
The Canon EF 50mm f/1.8 STM (Amazon, B&H) is as light and small as the Canon RF 50mm f/1.8 STM (Amazon, B&H).
Canon claims that the RF version has smoother and a quieter autofocus. That would be great, because EF lenses have noisy motors for continuous AF.
The major difference is obviously the construction. The EF 50mm f/1.8 STM has a worse focus ring and is not that well constructed. The RF version is better and the focus ring is also a customizable control ring that can be customized to change exposure on the go. This is only available on cameras that natively have an RF mount.
The RF 50mm f/1.8L has the same amount of aperture blades and is of the same weight and size. What it does better, according to Canon, is better flare and ghosting performance due to a better coating. It also has different optics that keep distortions and chromatic aberrations down.
Features
Coverage
The RF 50mm f/1.8 STM (Amazon, B&H) is a full frame lens. It is designed to completely cover a sensor the size of 36mm x 24mm.
If you are considering this lens for an APS-C sensor or other cinema camera, check out this article:
Focal Length
The focal length is 50mm. This is considered normal on a full frame 35mm sensor.
This focal range is very useful for mid shots, interviews, and close ups.
Aperture
The maximum aperture is f/1.8 and the minimum aperture is f/22.
Having f/1.8 is great for low light. Most people will use it at f/1.8 or f/2 for this purpose, and to get soft out of focus backgrounds.
The RF 50mm f/1.8 STM (Amazon, B&H) has 7 rounded diaphragm blades. One expects a smooth bokeh but it’s not always a given. If you want more blades, you might want to take a look at the Canon Sumire primes. To know more about bokeh:
Resolution
From Canon’s official MTF charts:
The Canon RF 50mm f/1.8 STM (Amazon, B&H) is okay-sharp in the center (not as good as the L-series primes) and falls off quickly. I believe the chart is at f/1.8. In that case this is expected and is on similar lines compared to the EF version.
People expect this from an f/1.8. “kit” lens.
With the variance in the Sagittal and Tangential lines, you can infer (somewhat) that the bokeh won’t be proportionally smooth as the best prime lenses on the planet. However, it should be decent, and they correlate to each other well so there is some harmony in the design.
If you really want this lens at its sharpest you’re better off stopping down to f/2 or even f/2.8 for best results.
If you are curious and want to read the MTF chart for yourself. Here’s a guide on how to read them easily.
Close Focus
The closest focusing distance is 0.3 meters or 0.98 feet. That’s nice for this focal length because you can also use it for close ups.
Image Stabilization
The Canon RF 50mm f/1.8 STM (Amazon, B&H) lens doesn’t have Image Stabilization. This is a disappointment, because that would have made it a lot better than the EF version.
Pairing the 5-axis IBIS-equipped Canon EOS R5 or Canon EOS R6 with this lens can deliver some level of stabilization, so all is not lost. This can be toggled on and off if you choose so.
Control
Manual focus system
By default the Canon RF 50mm f/1.8 STM (Amazon, B&H) is set to ‘fly by wire’.
Even though the Canon RF focus ring is technically a ‘focus by wire’ system, the RF lenses are the first line of lenses in the world which have enabled turning focus by wire off.
There’s no “AF/MF” switch on the lens. You get to pick between FOCUS and CONTROL (see photo above). When it’s set to FOCUS, rotating the control ring will provide Manual Focus.
You can always change the Focus Mode in the camera to MF to get manual focus.
What is the meaning of focus by wire and fly by wire?
Focus by wire: Let’s say you turn the focus ring to change focus from point A to B. You’d expect the focus to shift accordingly. When you stop point B will be in focus. Now bring the focus point back to A and try again, but at a different speed. Slower or faster, doesn’t matter. Now, even if you precisely rotate to the exact same degree, the focus will not be on point B! The speed of rotation determines which point it is focused on. That’s just completely useless for follow focus work. If an actor or person moves at a different speed, evens lightly, you’ll never get the same focus. Avoid focus by wire lenses like the plague (for video work).
Fly by wire: The distance of focus shifted is directly proportional to the speed at which the ring is turned. This is how a manual focus ring is supposed to operate for video and cinematography.
How to change to fly by wire on RF lenses
You can switch to ‘link to rotational degree’ where the focusing distance will be directly proportional to the rotational degree regardless of the rotational speed.
It is a quick two-step affair that requires you going into the Canon menu and switching the RF manual focus ring sensitivity to ‘linked to rotational degree’ instead of ‘varies with rotational speed’.
This feature will be exceptionally useful for anyone who wants absolute control over the focus ring.
This feature makes an RF lens a game changer for many videographers, filmmakers and cinematographers.
Autofocus system
Dual Pixel Autofocus is, without a doubt, one of the most revered video autofocus systems in the world. Canon claims the new AF actuators will help focusing to be smooth and phantom-quiet.
Canon claims that their STM motors are near silent, this we can only test in the field. The dual pixel AF system works better (in theory) than original EF lenses on native EF bodies. I don’t think anyone will be disappointed with its performance.
Control System
Canon RF lenses come with an extra customizable ring. Usually, in prime lenses the ring is a second ring, in addition to the zoom and focus rings. But in RF 50mm f/1.8 STM you only have one ring but the lens has an option to switch the control ring from focus control to lens control.
Since there is not enough room on the lens, Canon has made this decision of integrating two rings into one.
This ring is only customizable with cameras that have a native RF mount, such as the Canon EOS R5/6 and Canon EOS C70.
To toggle the Control Ring on and customize it to control one of the exposure determinants, follow these steps:
- Go into Settings
- Go to the Customize dials option
- Select Control Ring and switch it to Enabled.
- Now you can customize it to control aperture, shutter speed, ISO and exposure compensation.
Some videographers will find it helpful in riding the aperture due to its favorable placement right on the lens close to the focus and zoom ring.
Although the turn of the ring appears to be smooth, there is a soft clicking sound. Some might find it inconvenient. If you want to remove the sound you can.
The clicking of the control ring on every RF lens is removable through a chargeable service fee of about $79.99 (depending on your country) at your nearest Canon service center.
Basics
Filter Thread
The Canon RF 50mm f/1.8 STM (Amazon, B&H) has a filter thread diameter of 43mm. This is an uncommon filter diameter. You might be well served to buy a larger filter and use a step-up ring.
Build Quality
The majority of the lens exterior is plastic, though the lens doesn’t feel cheap.
The optical design consists of 6 elements in 5 groups, including one aspherical element.
Size and Weight
The RF 50mm f/1.8 STM (Amazon, B&H) has a diameter of 69.2mm and a length of 40.5mm. It weighs around a mere 160 grams.
This lens is the very definition of nifty fifty!
Weather resistance
Canon claims that all RF lenses are weather sealed. But again this only holds true if the camera body you will be using is also weather sealed. No camera is truly and officially weather sealed, so the best you can hope for is reliable weather resistance.
Beware of the fact that this lens is not an L series lens and will not perform as such.
What’s in the box
This is what you get in the box (other than the lens):
- Lens cap (E43)
- Lens dust cap (D1)
And that’s it.
Alternatives to the Canon RF 50mm f/1.8 STM Lens
The Canon RF 50mm f/1.8 STM (Amazon, B&H) is a great all purpose kit lens. There are only two “alternatives”:
- Non recommended: Canon EF 50mm f/1.8 STM (Amazon, B&H) – same aperture, slightly cheaper, worse optically and mechanically – and don’t forget you need to add an adapter to get it to work. Not worth it.
- Expensive: Canon RF 50mm f/1.2L USM (Amazon, B&H) – Expensive but with a wider aperture. It’s heavier and bigger. It has a farther focusing distance and also a USM motor. Recommended for people who need f/1.2 and better optical image quality.
I hope you found this overview of the Canon RF 50mm f/1.8 STM (Amazon, B&H) useful. If we have missed out on something, please let us know in the comments below.
