Canon RF 400mm F2.8 L IS USM Lens Review

Canon RF 400mm F2.8 L IS USM Lens

The elite Canon RF 400mm F2.8 L IS USM is an absolutely no-compromise, professional-grade, ultra-high-performance lens that delivers stunning, standout imagery. This lens is the ultimate choice for action sports and often the best option for wildlife.

  • Outstanding choice for sports and wildlife
  • Extremely sharp
  • Ultra-wide aperture
  • Incredible background blur
  • Fast AF
  • Professional grade
  • Optical image stabilization
  • Compatible with RF extenders
  • Full featured
  • Super expensive
  • Large
  • Heavy
  • Low maximum magnification
  • No Control Ring
In-Depth Review

I introduced the Canon EF 400mm f/2.8L IS III USM Lens as the lens of your dreams. The Canon RF 400mm F2.8 L IS USM Lens is the same lens in an RF mount.

Let me explain that statement with a brief introduction to this model before diving into the full review. You need to know that the Canon RF 400mm F2.8 L IS USM Lens, with a brushed metal EF to RF mount adapter built in and focus distance window removed, is essentially the same as the Canon EF 400mm f/2.8L IS III USM Lens with a Mount Adapter EF-EOS R behind it and a new wiring system in it. This includes optical and mechanical performance.

Canon RF 400mm F2.8 L IS USM Lens Mount

It is easy to say that Canon took the easy option when creating the 400mm f/2.8 for the RF mount, and it is also hard to argue against that statement. However, it is unlikely that today's optical advances were significant enough to justify a new design since the EF lens introduction less than three years earlier. Also notable is that long focal length lenses tend to benefit less from the short flange distance on the mirrorless camera models, reducing the justification for a redesign.

Why bother introducing the RF model if the mount is the only significant design improvement, and compatibility with EOS DSLR Cameras is foregone? Eliminating the mount adapter creates a slightly tighter, more secure fit and reduces weight slightly for two minor benefits. That the adapter is no longer at risk of being forgotten or lost is a benefit.

Canon RF 400mm F2.8 L IS USM Lens Top View

An interesting benefit provided by the technology in the RF mount (specifically) is a CIPA image stabilization assistance rating increase to 5.5 stops from 5 stops.

Perhaps the biggest benefit of the built-in RF mount is compatibility with the Canon RF 1.4x and RF 2x Extenders, compatibility that the Canon mount adapter (probably) should have availed. The RF extender and lens combination produces improved image quality over the EF models.

Overall, the RF lens is practically the same as the EF lens, and much of this review will be the same (including many of the sample pictures).

If you can get past the price, the RF 400mm F2.8 L IS USM Lens will blow you away in most other regards. This is one of the most incredible lenses available, and it is the ultimate action sports photography lens. The RF 400mm F2.8 L IS USM features impressive image quality at even wide open apertures, incredibly fast AF, and best-available build quality. That is what I said at the beginning of the Canon EF 400mm f/2.8L IS II Lens review, it still applies to the version III lens, and it now applies to the RF lens.

The RF 400mm F2.8 L IS USM Lens is the 7th generation in Canon's 400mm f/2.8 series, and the 4th IS version. Owners of this lens will, like owners of the previous lens versions, primarily be professional and serious amateur photographers (or simply wealthy). Due to this lens's focal length and max aperture, these photographers will mainly use this lens for sports, wildlife, and photojournalistic pursuits.

The bar was set extremely high for the EF version III lens. That lens's predecessor was simply phenomenal in all respects. A new version could be nothing less, and it was hard to believe that better was achievable. Amazingly, it was.

While at first glance, the Canon EF 400mm f/2.8L IS III USM Lens looks like the II, the appearance seems more accidental than intentional as the III is a entirely new lens design with the most apparent difference being dramatically lighter weight. Photographers have many opinions about what they want in a lens, but universal for this one lighter weight. With the version II lens dropping 3.3 lbs (1,520g), it was hard to imagine a significant additional weight loss delivered only seven years later. However, the version III lens saw substantial additional weight loss.

Let's put the Canon super-telephoto weight loss program into a chart:

Canon RF 400mm F2.8 L IS USM Lens6.4 lb(2890)2021
Canon EF 400mm f/2.8L IS III USM Lens6.3 lb(2840)2018
Canon EF 400mm f/2.8L IS II USM Lens8.5 lb(3850)2011
Canon EF 400mm f/2.8L IS USM Lens11.8 lb(5370)1999

The RF 400mm F2.8L IS USM Lens weighs only approx. 6.37 lbs (2,890g). That is approximately 2.1 lbs (960g) less than the version II lens (25% less) and an incredible 5.5 lbs (2,480g) less than the version I lens (46% less).

Canon EF 600mm f/4L and EF 400mm f/2.8L IS III USM Lens Introduction

Upon the curtain going up at the announcement event for the EF III lens (Elliot Peck, Canon USA Senior VP & GM shown above), I held both lens versions simultaneously. The difference felt even more significant than the numbers show, and the weight shifted rearward, giving the lens a better balance, is part of the reason for this.

So, how were the weight savings and improved balance created?

The Canon-supplied graphics below show the design of the last three Canon EF 400mm f/2.8 image-stabilized lenses. Light green represents UD elements, violet indicates a fluorite element, and dark green elements are Super UD.

Canon EF 400mm f/2.8L IS III USM Lens Design

Notice that the protective meniscus front lens element in the I series lens disappeared in the II, with a less-expensive-than-UD next-in-line element becoming frontmost. Additional weight reduction was found in the utilization of fluorite elements.

The III's biggest design secret is moving all but one of the large front set of lens elements considerably far rearward, where they also become smaller. As mentioned, this design also moved the center of gravity rearward for better comfort and handling. The front of the lens gets moved the most, and it is now considerably lighter, though, with decreased momentum, the new lens is not as easy to hold stationary.

The addition of the Super UD element was part of the design change. Check out that awesome 3rd lens element, a thin concave optic tightly nested between the two fluorite elements. Per Canon, "This lens element is so delicate that simply holding the edges of it in your hand can cause localized warping due to body heat."

Interestingly, the EF 600 III and EF 400 f/2.8L IS III lenses were the first Canon designs featuring new glass materials. "This glass has a comparatively higher refractive index than general low-dispersion glass, and has a low specific gravity. By using the new glass material in the first, large-diameter lens element [which cannot be reduced in size due to the focal length and max aperture requirements], the weight is reduced and spherical and chromatic aberration are suppressed." [Canon]

Another interesting design element is the forward-positioned aperture, resulting in the largest EMD (electromagnetic diaphragm) in an EF lens or RF lens to date and representing another design challenge Canon has overcome.

Focal Length

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Your lens selection decision should always be significantly weighted to choosing the right focal length. While perspective remains important for telephoto lens focal length selection, distance-to-subject often becomes the bigger factor. How close can you get to the subject from the vantage points available to you? Or, how close do you want to get to the subject? Safety, for both the photographer and the subject, may be a factor in answering the second question.

While this lens has some amazing, unique features, its 400mm focal length is (should be) the same as that in all of the other 400mm lenses (including zoom lens options). Four hundred mm is a moderately long telephoto focal length that has a correspondingly narrow angle of view. What is the 400mm focal length commonly used for?

Action sports are always at the top of my mind when I'm thinking about 400mm subjects. I won't bore you with my attempt to create the entire list, but a huge number of sporting events are captured with this focal length. I'll talk more about the ultra-wide-for-400mm f/2.8 aperture soon, but that feature makes this lens the ultimate choice for many indoor sports and sporting events held under the lights. The 400mm focal length reaches mid-field on a big field event (soccer, football, baseball).

400mm Sports Sample Picture

This lens is my first choice for running events, including track and field meets. I also use it frequently for equestrian photography.

Canon EF 400mm f/2.8L IS III USM Lens Sample Picture

The 400mm focal length finds a lot of wildlife in front of it. Wildlife is typically most active early and late in the day when the light is dim, and the f/2.8 aperture is a great complement to the narrow angle of view. The weight of this lens, along with the focal length, makes it a good choice for birds-in-flight.

Photojournalists and others covering events will love this lens's reach, especially combined with the f/2.8 aperture. When these photographers are not permitted close access to their subjects, including concerts, speaking events, etc., this focal length will often provide the reach needed.

While 400mm is long for portraiture, and the working distance 400mm requires can present communications issues with the subject, the results of making this work can be awesome. I often use 400mm lenses for landscape photography, but this lens's size, weight, and cost will prevent most from selecting it specifically for that purpose. However, if you have the lens and the opportunity arises, the RF 400 can work impressively for this endeavor, capturing mountain vistas, fields of flowers, colorful foliage, etc.

Utilizing a smaller portion of the image circle means that APS-C sensor format cameras frame a scene more tightly, with 1.6x being the angle of view multiplier (FOVCF) for Canon's lineup. To date, no RF mount cameras have an APS-C imaging sensor. Should such a camera become available, 400mm's full-frame angle of view equivalency is 640mm. The uses for 400mm on an APS-C body shift toward big field sports and longer-distance wildlife. It is an ideal option for both.

Let's briefly discuss optimal framing with a prime lens. Image cropping is often required during post-processing after using a prime (non-zoom) lens to capture the action from a fixed position, as is frequently the case with sports photography. A longer focal length lens has a narrower angle of view, which requires you to be farther from the subject for optimal framing. One huge advantage that a narrower angle of view provides is a longer duration to capture an optimally-framed subject. That advantage can result in less cropping needed overall with higher resolution retained.

Let me explain that concept. If you are shooting a running person with a 24mm lens on a full-frame format DSLR, the optimal framing distance to capture the entire person might be 9' (3m). At 18' (6m), that person would only be 1/2 of the optimal size in the frame. A person running at full speed will only momentarily be near that optimal distance.

In contrast, a 400mm lens would frame this person similarly optimally at around 135' (42m), with the 1/2 optimal distance being 270'. It takes a running person far more time to cover this 135' (42m) 1/2 to optimal distance than the 24mm lens's 9' (3m) distance. Distances much closer than optimal will often result in the subject being cropped in the frame, so I'll not count this distance. The longer the subject remains at near-optimal framing distance, the more time you have to capture ideally framed shots, and you can cover a much greater area of the event from a single position.

This explanation does not say that a 400mm lens is always a better choice, but it is the right answer for many sports events. There are longer focal length lenses available, and those lenses provide even larger areas of optimal coverage. But, those longer lenses do not offer the incredible f/2.8 aperture advantage.

Here is a focal length comparison to see how the 400mm focal length range fits into other popular options (created with a different lens).

Focal Length Range Example

Which focal length is best? That answer always depends on the subject and the scenario.

Max Aperture

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The Canon RF 400mm F2.8 L IS lens's massive f/2.8 aperture is the biggest contributor to its large size, heavy weight, and high cost, but that aperture opening is also the key to its awesomeness. Canon has numerous great 400mm-capable lenses, but none of them has an aperture more than 1/2 as large as this RF lens (and its EF version III equivalent). Four hundred mm is the longest focal length Canon-mount lens available with an f/2.8 max aperture, aside from the monster Sigma 200-500mm f/2.8 EX DG APO IF Lens, a lens that few have been willing to pay for or carry.

Allowing a great amount of light to reach the camera's imaging sensor positions this lens as the ultimate choice for long focal length low light needs. If shooting sports events indoors or outdoors under the lights, f/2.8 is often the narrowest aperture useful for stopping motion unless resorting to noisy-high ISOs.

One stop wider makes a big difference over an f/4 lens. It can be the difference between obtaining a shutter speed that captures a sharp image and one that delivers blur, and the two-stop difference over an f/5.6 alternative is huge.

In moderately low light levels where the other lenses can work, this lens can capture images at one or two-stop lower ISO settings, usually resulting in far lower noise levels. For example, at ISO 3200, this lens can stop action that an f/5.6 max aperture lens requires ISO 12800 to stop. That resulting noise level difference is significant.

Another important camera feature that works better with the large amount of light provided by this lens's aperture is the AF system. Subjects for 400mm lenses are often in motion, and the increased AF performance can be a key to in-focus images.

In addition to permitting a significant amount of light to reach the imaging sensor, the 400mm f/2.8 combination can produce a shallow depth of field that, combined with strong telephoto magnification, can blur the background stronger than nearly all other lenses. Most of the common uses for this lens do not permit manipulation of the background, and the background of the venues this lens gets used in tend to be busy and distracting. Use this lens to blur the background away, turning advertisement banners, fans, and their clothing, apparatus, gear, seating, etc., into only blurs of color, making the subject stand out, popping from the frame. Look at the images in the popular sports magazines/websites to see the results this lens can achieve.

Here is an aperture comparison that was created using the version II Lens.

Aperture Comparison

Canon's most affordable professional-grade 400mm lenses, including the Canon RF 100-500mm F4.5-7.1 L IS USM Lens, have a max aperture of f/5.6 or narrower at that focal length. As illustrated above, the background blur difference between 400mm f/2.8 and 400mm f/5.6 is substantial.

Here is a sample photo illustrating the background blur strength of this lens, even with a full horse and rider comfortably framed in a modestly cropped image.

Canon EF 400mm f/2.8L IS III USM Lens Background Blur Sample Picture

When shooting action and portraits with this and similar lenses, I seldom use an aperture other than f/2.8. Since those are my primary subjects for this lens, I might not notice if this lens had only f/2.8 available, and I probably wouldn't complain if I did notice.

Image Stabilization

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Practically everything in the EF III lens was new, including the image stabilization system that has achieved an impressive up to 5-stop CIPA rating. The RF lens gets a slightly higher 5.5 stop rating, with the increase directly attributed to the RF mount. Note that this lens does not support coordinated IS, but IBIS is said to still provide some benefits.

The RF and version III lenses are far lighter than the previous generation lenses, but these are still not light lenses to handhold. Handholding the III completely unsupported (no help from an elbow resting against the body) for the many hundreds of images required for a complete image stabilization test session was a big workout. I learned that, under ideal conditions, my keeper rate with 1/25 second exposures was high, and it was still quite good at 1/20. Just over 60% of the images captured at 1/13 second were sharp, and a couple of additional images from that set could have been usable with some additional sharpening added. The sharp image rate dropped off gradually until the last sharp images were captured at 1/6 of a second.

Keep in mind that this EF version III testing was done on an ultra-high resolution Canon EOS 5Ds R. Higher imaging sensor pixel density makes motion blur more-readily-noticeable than lower resolution models as details cross over pixel wells with less movement. Basically, motion is being magnified by the tighter spacing of pixel wells.

Three IS modes are provided as with many of Canon's L-series telephoto lenses. Mode 1 (general-purpose), Mode 2 IS (for panning with a subject, one axis of stabilization is provided), and Mode 3. Mode 3 is useful for tracking erratic action. In this mode, image stabilization is active and ready for use the moment the shutter releases, but actual stabilization is not in effect until that precise time. As a result, the viewfinder is not stabilized, allowing erratic subject motion to be tracked without fighting against image stabilization trying to stabilize the view. IS Mode 3 is designed to detect panning motion, and when detected, the lens will only apply Image Stabilization at right angles to the direction of the detected movement (like IS Mode 2). The latest word I've heard from Canon is that mode 1 can optimally be used for nearly all situations, including while using a tripod or monopod and while photographing action.

A noticeable click is heard when IS starts and again when it stops, but only quiet whirring and clicking are audible while IS is active. This IS implementation is exceptionally well behaved – the image in the viewfinder does not jump around when the system activates, and the image does not drift while IS is active. IS aids greatly in establishing ideal subject framing, and I had no problem tracking action in Mode 1.

Canon's super-telephoto lenses have a secondary IS mode that automatically senses a tripod in use, then attempting to eliminate shutter shock, wind vibration, and other sources of remaining movement.

While stopping camera motion-induced image blur is image stabilization's primary job, it has another significant benefit, aiding in AF precision. The camera's AF system can produce better focus precision if the image it sees is stabilized. Canon contends that this is true even with a subject that is in motion, and AF precision is especially critical with the 400mm f/2.8 combination producing a potentially shallow depth of field.

The RF and EF version III lenses can be handheld for significant periods, and the image stabilization system in these lenses greatly extends their versatility in that regard.

Image Quality

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We're reviewing another big white Canon super-telephoto lens, so it is time to dig out all of those big superlatives to describe the image quality. With the version II lens delivering incredible image quality, there was little room for improvement with the III. But, few would be tolerant of any decline in image quality despite the weight reduction. Fortunately, there was no need for concern. The version III lens delivers absolutely outstanding image quality, the RF lens version has the same optics, and many of the examples below are from the EF III lens.

With f/2.8 aperture being so crucial for this lens, the wide-open image quality matters most, and you will love the results from this lens. It performs spectacularly at f/2.8, delivering razor-sharp details across the entire full-frame image circle. Very few lenses perform near their best at wide-open apertures, but little resolution or contrast improvement is seen from this one at f/4 or narrower apertures, and none is needed. The only reason to stop this lens down is for increased depth of field and slightly less peripheral shading in the corners. That is the way it should be.

Our lab sharpness tests tell the story the best, but I attempted to create some outdoor comparison examples to share. To eliminate variations, outdoor testing requires the stable lighting of a clear sky, and heatwaves are often present when the sky is clear. When magnified with a 400mm lens, heatwaves distort results. I was not able to satisfactorily overcome that problem, so I'm opting to share some 100% resolution f/2.8 crops instead. These images were captured using an ultra-high resolution Canon EOS 5Ds R with RAW files processed in Canon DPP using the Standard Picture Style and sharpness set to only "1" (0-10 scale). Note that images from most cameras require some level of sharpening, but too-high sharpness settings are destructive to image details and hide the deficiencies of a lens.

Canon EF 400mm f/2.8L IS III USM Lens Sharpness Comparison Example

Find the center of the depth of field in the above samples to identify the correct performance. The feather detail image is my favorite for showing what this lens can do at f/2.8.

I debated about including the following corner comparison for a couple of reasons. One is that, as mentioned, heatwaves were a big issue, and another is that the shallow depth of field at a distance close enough to avoid some of the heatwave issue made the comparison a bit challenging to discern. In the upper left corner crops below, look for the narrow area of details that change least between images. The second f/2.8 image, also a top-left-corner crop, was captured at a relatively long distance. This one has strong heatwave effects showing, but it still looks great.

Canon EF 400mm f/2.8L IS III USM Lens Corner Sharpness Comparison Example

I see a touch of improvement happening at f/4. A lot of the uses for this lens do not require tack-sharp corners, but when that need arrives, this lens will deliver impressively.

Focus shift, the sharp focus plane moving forward or backward as the aperture is narrowed (residual spherical aberration), is not an issue with this lens. Stop down, and the center of the depth of field will remain where you expect it to be.

I generally don't like vignetting, but I don't mind having some vignetting from lenses such as this one. Sports action and wildlife shots seldom have a primary subject (or a primary subject's face) in the corner of the frame, and the vignetting-darkened borders can draw the viewer's attention to the subject and their face. At f/2.8, this lens has just a touch of this effect. The about-1.5-stops of corner shading is mild and usually only slightly noticeable. The about-0.6-stops of shading in the f/4 corners is seldom noticeable, and if you cannot have any shading in your image corners, f/5.6 and narrower apertures have you covered.

Lateral (or transverse) CA (Chromatic Aberration) refers to colors of the spectrum being magnified differently. Lateral CA shows as color fringing along lines of strong contrast running tangential (meridional, right angles to radii) with the mid and especially the periphery of the image circle showing the most significant amount as this is where the most significant difference in the magnification of wavelengths typically exists.

With the right lens profile and software, lateral CA is often easily correctable (often in the camera) by radially shifting the colors to coincide. However, it is always better to avoid this aberration in the first place.

Color misalignment can easily be seen in the site's image quality tool, but let's also look at a worst-case example. The image below is a 100% crop from the extreme top left corner of an ultra-high-resolution EOS 5Ds R frame showing diagonal black and white lines.

Canon EF 400mm f/2.8L IS III USM Lens Lateral Chromatic Aberration Example

There should be only black and white colors in these images, essentially what we see here.

A relatively common lens aberration is axial (longitudinal, bokeh) CA, which causes non-coinciding focal planes of the various wavelengths of light. More simply, different colors of light are focused to different depths. Spherical aberration along with spherochromatism, or a change in the amount of spherical aberration with respect to color (looks quite similar to axial chromatic aberration but is hazier) are other common lens aberrations to observe. Axial CA remains somewhat persistent when stopping down, with the color misalignment effect increasing with defocusing. The spherical aberration color halo shows little size change as the lens is defocused, and stopping down one to two stops generally removes this aberration.

In the real world, lens defects do not exist in isolation, with spherical aberration and spherochromatism generally found, at least to some degree, along with axial CA. These combine to create a less sharp, hazy-appearing image quality at the widest apertures.

The example below looks at the defocused specular highlights' fringing colors in the foreground vs. the background.

Canon EF 400mm f/2.8L IS III USM Lens Spherical and Axial Aberration Example

The silver jewelry in the 100% crops from an f/2.8 5Ds R image above shows only slight color differences in the foreground vs. background, and the details in the center of depth of field are sharp, reflecting strong performance.

Canon optical technologies deployed on this lens include Super Spectra Coating (SSC), rejecting extraneous light wavelengths, and Air Sphere Coating (ASC, a thin film containing silicon dioxide and air formed on top of traditional multi-coating), helping to minimize glare and reflections. Additionally, the new optical design, moving the second lens element toward the rear of the lens with only one large element remaining in the front, aids in reducing flare and ghosting. Our standard flare test involves placing the sun in the corner of the frame. While this test works excellently with wide angles through short telephoto focal lengths, longer focal lengths such as this always show a lot of flare from this test.

This lens is near-linear-distortion-free, with only a tiny amount of pincushion distortion showing in our test. I doubt that you'll ever be tempted to distortion-correct a Canon EF 400mm f/2.8L IS III Lens image.

Very obvious is that this lens can create a crazy-strong background blur, and the quality of that blur is quite good. A pair of bokeh samples showing out-of-focus specular highlights are shown below.

Canon EF 400mm f/2.8L IS III USM Lens Bokeh Example

The images above were captured with the lens stopped down to f/8 for involvement of the 9-blade aperture. These are some of the nicest results I've seen. Aside from the requisite concentric rings around the borders of specular highlights, the outer transition is smooth and nicely rounded, and the centers smoothly filled.

How good is the optical quality of the Canon EF 400mm f/2.8L IS III Lens? It is stunning. I can't think of anything else to say, and that descriptor seems to sum it up accurately.


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Critical for the success of a lens with a shallow depth of field used primarily to photograph fast action is its AF performance. Canon's super-telephoto lenses have long delivered the best-available autofocus performance, and this lens continues that trend.

As you would expect, this lens gets all of the latest available upgrades — identical to the EF III. "Mechanically-related AF improvements include reduced drive load, thanks to glass materials in the focus lens group that are nearly one-fifth the previous weight." [Canon] Also included is the latest microprocessor for improved calculation speed. Canon claims a faster minimum focus distance to infinity focus time, despite a shortened minimum focus distance, than with the version II lens. That lens focused fast, so don't expect to find the difference dramatic, but this is a fast-focusing lens.

The Canon EF 400mm f/2.8L IS III USM Lens arrived, and it was time to unleash the ponies.

Canon EF 400mm f/2.8L IS III USM Lens Action Sample Picture

The horses are always ready for some galloping, and they provide both convenient and challenging subjects for AF performance testing. The Canon EOS-1D X Mark II and EF 400mm f/2.8L IS III Lens combo performed impressively with this subject, so well that they created a bit of a problem. It took forever to go through the well-over-2,000 images captured in this session, as most were keeper-grade. With a great camera behind this lens, a photographer's brain needs to be retrained to be OK with deleting really nice images. At least, that's what I keep telling myself.

In addition to being fast and accurate, this lens's internal AF system is quiet. Some quiet internal shuffling along with quiet clicks can be heard if you listen carefully, but I don't notice the sounds when shooting.

The RF super-telephoto lenses include a Focus Preset feature. Set the Focus Preset to a specific distance. When your shooting needs require that particular distance, turn the white spring-loaded playback ring located in front of the focus ring, and the lens will automatically adjust to the preset distance. New with the III is a direction-sensitive feature that permits a different distance to be set for each rotation direction. The Focus Preset switch settings include OFF, ON, and an ON with audible focus confirmation. Use this feature to quickly adjust focus to a known distance or to an approximate distance where fine-tuning can quickly attain proper focus.

A 3-position focus limiter switch allows focusing distances to be limited to a subset of this lens's focus distance range. In addition to the full range, restricted limits of 8.2' - 23.0' (2.5 - 7m) or 23.0' (7m) - ∞ can be selected for improved focus lock times and reduced focus hunting when photographing subjects at distances within these ranges.

Four autofocus stop buttons in the black ring near the objective lens allow autofocus to be temporarily stopped. I use AI-Servo (continuous) focusing mode for shooting sports but sometimes shoot focus-and-recompose images such as portraits during the event. The autofocus stop feature makes it easy to obtain focus lock, turn off autofocus, and recompose for a framing that places the active focus point(s) off of the subject, including in the periphery of the frame. Another excellent use for this feature is when an image has been captured with suboptimal framing. Simply press a focus stop button and then capture enough images to be stitched together during post-processing. Of course, switching the lens to manual focus mode also works for these techniques.

New on the 2010-announced super-telephoto lenses was a third focusing mode. In addition to AF and MF, a "PF" or Power Focusing mode was included, and this mode has returned with the series III lenses. When first introducing this feature, Canon USA said the feature helped "...moviemakers achieve smoother and more appealing focus shifts when filming."

Turn the focus preset playback ring (very) slightly to get low-speed electronically-driven AF, and turn it to a greater degree to obtain a higher rate, with the direction of ring rotation determining the direction of focus distance change. The feature works nicely, but you will need a solid tripod setup and a steady hand not to induce movement while turning the ring. The power focusing is extremely quiet. Note that AF does not work in PF mode, though manual focusing is available in this mode.

Those interested in manually focusing this lens have definitely not been forgotten – this ring lens provides a superb manual focus experience. Instead of a conventional mechanically-linked manual focus drive, Canon implemented electronic manual focusing in the EF III lens, the first Canon super-telephoto (along with the EF 600mm f/4L IS III) to have such. This decision simplified the overall design, saving weight and increasing expected reliability. Perhaps your first clue about this being a focus-by-wire design will be when attempting to manually focus with the camera powered off or the metering inactive. This feature no longer works.

This lens's manual focus ring is ideally located, has a sharply-ribbed rubber surface with a great feel, is large, and is smooth with no play and an ideal rotational resistance. A series of tightly-spaced click sounds are audible while manually focusing.

A feature commonly implemented on electronic focusing lenses is variable speed drive rate dependent on the focus ring rotational speed. Unfortunately, this feature is often not optimally implemented, and fortunately, Canon has a better option for this lens. Via a switch, this lens offers three linear drive speeds. Mode 1 adjusts the focus more slowly than on the II series, and precise focusing is challenging in this mode. Mode 2 and 3 become respectively slower, enabling fine control of the focus distance. You don't want to use the 3 setting to chase sports action, but this mode allows for precise manual focusing.

FTM (Full Time Manual) focusing is supported in AF mode while in One Shot Drive Mode, but the shutter release must be half-pressed for the focus ring to be enabled. Note that FTM does not work if electronic manual focusing is disabled in the camera's menu (if this option is present). The lens's switch must be in the "MF" position and the camera meter must be on and awake for conventional manual focusing to be available.

Cameras featuring Dual Pixel CMOS Movie Servo AF make video recording easy, and this lens is well-suited for this task. The smooth focusing makes focus distance transitions easy on the viewer's eyes, and the camera's mic does not pick up the sound of the lens focusing.

A focus distance window is not provided on this lens (one is included on the EF III).

Canon super-telephoto lenses are not known to have the shortest minimum focusing distances among lenses in general. The good news is that the Canon RF 400mm F2.8 L IS USM Lens improves upon its version II predecessor's spec, dropping the close distance to 8.2' (2500mm) from 8.86' (2700mm). Still, the .17x maximum magnification spec is unchanged. This lens is an only mediocre performer among all lenses in this regard. Our subject framing distance measurements show this.

As illustrated below, expect a modest subject magnification change in a full-extent focus distance adjustment.

Canon EF 400mm f/2.8L IS III USM Lens Focus Magnification Example

Following is a comparison table showing the recent and current Canon super-telephoto lineup as of review time.

ModelMin Focus Distance "(mm)Max Magnification
Canon RF 100-300mm F2.8 L IS USM Lens70.9(1800)0.16x
Canon RF 100-500mm F4.5-7.1 L IS USM Lens35.4(900)0.33x
Canon EF 200-400mm f/4L IS Ext 1.4x Lens78.7(2000)0.15x, 0.21x
Canon RF 200-800mm F6.3-9 IS USM Lens31.5(800)0.25x
Canon EF 300mm f/2.8L IS II USM Lens78.7(2000)0.18x
Canon RF 400mm F2.8 L IS USM Lens98.4(2500)0.17x
Canon EF 400mm f/2.8L IS III USM Lens98.4(2500)0.17x
Canon EF 400mm f/2.8L IS II USM Lens106.3(2700)0.17x
Canon EF 400mm f/2.8L IS USM Lens118.1(3000)0.15x
Canon EF 400mm f/4 DO IS II USM Lens129.9(3300)0.13x
Canon RF 600mm F4 L IS USM Lens165.4(4200)0.15x

A subject measuring approximately 7.9 x 5.3" (202 x 135mm) fills a full-frame imaging sensor at this lens's minimum focus distance.

Magnification from telephoto focal length lenses is not significantly increased with extension tubes, hollow tubes (with electronic connections) that shift a lens farther from the camera. This shift allows the lens to focus at closer distances, though at the expense of long-distance focusing. A 12mm extension tube increases the magnification range to 0.22-0.03x, and 0.3-0.07x results from mounting a 25mm extension tube. As of review time, Canon does not have RF mount-compatible extension tubes available, but third-party options are available. I often used extension tubes with the IS version I lens, especially when photographing birds and small mammals. With the minimum focus distances decreasing on the version II and III lenses, I find less need for them.

Canon RF 400mm F2.8 L IS USM Lens with Teleconverter

Extenders / Teleconverters

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As mentioned at the beginning of this review, the Canon RF 400mm F2.8 L IS USM Lens is compatible with the Canon RF 1.4x Extender and the Canon RF 2x Extender.

Lacking an EF mount, this lens is not compatible with the Canon Extender EF 1.4x III and the Canon Extender EF 2x III.

With the 1.4x behind it, this lens becomes a 560mm f/4 IS lens. With the 2x mounted, it becomes a 800mm f/5.6 IS lens. Weather-sealing and image stabilization remain included and effective. The lens's native minimum focusing distance is retained with extenders in use, and that means the maximum magnification value is multiplied by the extender's multiplier, a significant improvement.

I didn't capture the following images with an extender focal length comparison in mind, but they work for that purpose.

Canon EF 400mm f/2.8L IS III USM Lens Teleconverter Focal Length Comparison

With the RF 1.4x behind the RF 400 L and a wide-open aperture selected, image sharpness is decreased modestly in the center in the center of the frame, but corners are nearly unaffected. Stopping down 1 stop to f/5.6 brings a nice improvement and impressive sharpness across the frame. The RF 1.4x adds a slight amount of barrel distortion but notably does not affect lateral CA.

As always, the image sharpness hit with the 2x extender is stronger than with the 1.4x, and the 800mm f/5.6 results are a bit soft (though the image circle periphery seems to take less of a hit). Stop down one stop to f/8, and the sharpness is good across the frame. The 2x increases lateral CA noticeably and barrel distortion slightly. Real-life results usually look better than our charts, but the 2x has an obvious impact on image quality, especially sharpness, a combination of contrast and resolution.

If you have tried extenders with smaller telephoto lenses in the past, it is worth trying them again with Canon's current lineup of super-telephoto lenses. Having a 400mm f/2.8, 560mm f/4.0 IS, and 800mm f/5.6 IS available in a quick lens change is valuable.

The with-extender autofocus performance I am experiencing is excellent. Unless the scene is extremely defocused, it is difficult to tell that the extender is even in place in regard to AF. Typically, low light performance can be decreased modestly with extenders reducing the maximum aperture.

Canon RF 400mm F2.8 L IS USM Lens Side View

Build Quality & Features

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Canon's big white super-telephoto lenses are among the most elite lenses available and represent the Canon L Series's best. Professionals expect these lenses to deliver the ultimate performance in the most adverse environments, and with the version III lens, the bar was raised. Despite the significant weight loss, the RF and EF version III lenses' overall durability was increased over the already-impressive version II model.

Improvements in manufacturing processes get some of the credit for the enhancements, and fascinating is the use of a new carbon-reinforced magnesium alloy. "The high level of fluidity in this material enables injection molding (thixomolding) for a thin walled formation. For example, with the first group lens barrel on the 400mm model, we were able to achieve a barrel thickness of 0.8mm via injection molding, for a base that is 20% thinner than previous models, maintaining sufficient strength and lightness. The carbon reinforced magnesium alloy is also used for the tripod base plate and the exterior of the barrel." [Canon]

As lens size increases, the difficulty to maintain precision increases, and it has been interesting to see the attention to detail given to this lens.

Upon loading the standard product images for the Canon EF 400mm f/2.8L IS III USM Lens, the first side-by-side comparison I wanted to see was of the three 400mm f/2.8 IS versions.

Canon EF 400mm f/2.8L IS Lens Version I, II, and III Comparison

At first glance, it appears that little has changed between the II (center) and III (left), but upon closer inspection, it seems that nearly everything has been changed. Hit the last link above to see larger versions of these images, but note that the tripod collar and foot have been moved significantly rearward, reflecting the much-improved weight distribution of this significantly lighter lens. The RF lens adds a built-in brushed aluminum mount adapter.

Canon RF 400mm f/2.8L IS III USM Lens Product Images

At the mount end of the lens, there is little change from the version II lens. The AF/PF/MF switch and the focus limiter switch are easy to find and use in this location. The focus limiter switch gets a new number reflecting its reduced minimum focus distance.

The tripod collar lock knob got a new texture that is easier to roll between the thumb and finger. With the tripod collar shifted back, the main switch bank could be moved rearward for easier access. The switches available on the next switch bank have already been discussed, but notice the additional manual focus speed switch gained over the version II lens.

Canon RF 400mm F2.8 L IS USM Lens Switches

All of this lens's switches are mostly recessed, with just enough raised surface to be usable with gloves on. Note that the IS ON/OFF switch is raised in the center vs. both sides for tactile differentiation.

As already mentioned, the focus ring feels great, and the shape of this ring aids in the quality experience. The focus recall ring received a new, much-improved look and feel on the version III lens. The black grip ring also received a new diamond pattern that sticks to fingers.

Notably missing on this RF lens is a control ring.

You may have noticed that the RF and III lenses are slightly brighter in color than the II, which itself is much whiter than the version I lens. The color of this lens deserves additional attention.

Heat gain, especially uneven heat gain, can cause problems for a lens's optical performance, and big lenses have a lot of surface area to catch sunlight. Canon has chosen white paint to avoid as much heat gain as possible, and the new paint formulation better shields the lens from heat than the previous paint did. "Infrared reflective pigments with high reflectance and titanium oxide lens barrel coating with silica provide excellent UV weather resistance and heat reduction." [Canon] But, that is just the beginning of the heat-avoidance efforts designed into the RF and version III lens.

A newly-developed heat shield coating reduces uneven heating, and a two-layer barrel structure design also helps mitigate thermal transfer effects into the lens elements. Reducing the weight of the lens naturally reduces its overall thermal capacity.

Canon EF 400mm f/2.8L IS III USM Lens Weather Sealing

The RF and EF version III lenses have the same weather-resistant construction as the II series lens, which is excellent. Many outdoor events are held regardless of the weather, and the photographers required to cover them are forced to deal with the weather. While I recommend a rain cover when wet weather is expected, it is the unexpected that can be a problem. I've used Canon weather-sealed super-telephoto lenses in some rather heavy rain with no ill effects. In addition to being sealed from moisture, dust is another hazard this lens keeps out.

The front and rear lens elements are fluorine-coated for easier cleaning and for preventing dust and drips from adhering in the first place.

Canon EF 400mm f/2.8L IS III USM Lens Fluorine Coating

You will immediately feel the ultra-high-quality construction when you pick up this lens. You will also feel the already-discussed significant weight loss from the version II lens. The difference is incredible. Carrying and using this lens causes less fatigue than when using the II predecessor, keeping the photographer sharp in the game. The lighter weight can reduce arm, back, and especially shoulder injuries that photographers commonly endure, and easing travel weight restriction challenges is valuable.

This lens can easily be handheld for reasonable periods – for many hundreds of images in the IS testing segment of this review. Still, this is a 6.37 lbs (2.89kg) lens. Those used to the version II's weight will find this lens a feather-weight, but those using smaller lenses such as the Canon RF 70-200mm F2.8 L IS USM Lens will require a bit of acclimating.

The size of this lens garners attention. You look like you belong in some venues, and you stand out in others. You'll get over the latter. Regarding the former, this lens is sometimes a ticket to access. This lens and others like it have gained me entrance to locations in venues that I would otherwise have been restricted from.

Here is a table of comparable Canon telephoto lenses with the weight specification included.

ModelWeight (lbs/)Dimensions w/o Hood ("/)FilterYear 
Canon RF 100-300mm F2.8 L IS USM Lens5.84(2650)5 x 12.7(128 x 323.4)1122023
Canon RF 100-500mm F4.5-7.1 L IS USM3.01(1365)3.7 x 8.2(93.8 x 207.6)772020
Canon RF 200-800mm F6.3-9 IS USM Lens4.52(2050)4.0 x 12.4(102.3 x 314.1)952023
Canon EF 200-400mm f/4L IS 1.4x Lens7.98(3620)5.0 x 14.4(128.0 x 366.0)DI 522013
Canon EF 300mm f/2.8L IS II USM Lens5.19(2350)5.0 x 9.8(128.0 x 248.0)DI 522011
Canon RF 400mm F2.8 L IS USM Lens6.37(2890)6.4 x 14.4(163.0 x 367.0)DI 522021
Canon EF 400mm f/2.8L IS III USM Lens6.27(2840)6.4 x 13.5(163.0 x 343.0)DI 522018
Canon EF 400mm f/2.8L IS II USM Lens8.49(3850)6.4 x 13.5(163.0 x 343.0)DI 522011
Canon EF 400mm f/2.8L IS USM Lens11.85(5370)6.4 x 13.7(163.0 x 349.0)DI 521999
Canon RF 600mm F4 L IS USM Lens6.81(3090)6.6 x 18.6(168.0 x 472.0)DI 522021
Sony FE 400mm f/2.8 GM OSS Lens6.38(2895)6.2 x 14.1(158.1 x 359.0)DI 40.52018

For many more comparisons, review the complete Canon EF 400mm f/2.8L IS III USM Lens Specifications using the site's Lens Spec tool.

The RF 400 is light and handholdable, but I still prefer to use this lens on support for both comfort and stability reasons. Simply adjusting the monopod while tracking sports action is much easier with the lighter, rear-weighted lens. Also, it is easy and fast to lift the monopod off the ground to follow action handheld. Use the monopod to rest the setup between breaks in the action.

Use the site's product image comparison tool to visually compare the Canon EF 400mm f/2.8L IS III USM Lens to other lenses. I preloaded another interesting comparison in that link.

The RF 400 F2.8 L IS utilizes the same 52mm drop-in filters as its predecessors and most of Canon's super-telephoto lenses. This lens's slot includes a drop-in filter holder that accepts 52mm threaded filters. A slim Canon Protect 52mm threaded filter comes installed (also helpful for catching dust before it drops deep inside the lens). Note that the filter is part of the optical design of Canon's big lenses, effectively the rear element in the lens design. The Canon Drop-In Circular Polarizing Filter PL-C 52 (WIII) is the filter option that will usually be found most helpful. This filter has had several revisions for color changes, keeping up with the lens color changes. Some will find neutral density filters helpful for this lens, especially when recording movies at f/2.8 under bright daylight.

With this lens's weight being comfortable for handholding, how this lens is handheld becomes a bigger issue. The shifted-rear weight distribution necessitated the tripod foot be moved back, and the tripod foot is the natural choice for holding this lens in use. The tripod foot height and the new rearward location combine to permit the left elbow to rest against the body for less shoulder strain. The version III foot's redesigned shape, including an upward curve at the end, makes handholding comfortable with fingertips ideally positioned for using the focus ring and the thumb located not far from the switches. The gripped padding provided on the tripod foot aids in carrying comfort.

This tripod foot has two differently-sized threaded inserts (1/4" and 3/8"). A Wimberley P50 Lens Plate permits quick attachment to Arca-Swiss compatible monopod and tripod head clamps. Mounting with two screws is important to prevent the plate from twisting, but note that most lens plates will require a 3/8"-16 to 1/4"-20 Reducer Bushing in the larger threaded insert. These are inexpensive, and it seems Canon could easily have included one in the box. Much better would have been to machine the needed Arca-Swiss dovetail grooves into the foot, as some other lens manufacturers have begun doing.

Replacing the Canon tripod foot with a Wimberley or Really Right Stuff Tripod Foot is popular and my preference.

The tripod collar is exceptionally smooth and provides light click stops at 90° degree rotations. While the click stops cause a small bump during rotation (such as when panning with a subject as a monopod tilts), I prefer to have the click stops assisting me with finding center, aiding significantly in keeping a camera level.

As the super-telephoto lenses continue to drop weight, the demands of the support they are used on also diminish. While this lens can be handheld for decent periods, you will still appreciate having support under the lens for longer periods of use (and for stabilizing the view). Avoiding future shoulder issues may not seem important today, but I assure you that you will one day appreciate having taken good care of your body in your youth. Keep your elbows in.

For tripod mounting, I suggest using a strong ball head (such as the Really Right Stuff BH-55 or Arca-Swiss Z1) with this lens. Much better (safer, easier) is to use a lens of this size on a gimbal style head such as the Wimberley WH-200-S Sidemount Head, Wimberley Tripod Head II, or Really Right Stuff PG-02.

Two tripod collar feet were included with the EF version II lens, with one being a small foot designed for monopods. I never used the small one, and apparently, many others left their small foot in the box as well. The smaller monopod foot is reportedly again available for the RF lens, but it is now an optional accessory.

As first seen on the 400 IS II, the RF 400 F2.8 has a Kensington-type wire security lock under the tripod collar lock knob cap.

Canon RF 400mm F2.8 L IS USM Lens Hood Comparison

The included ET-155 (WIII) lens hood is nearly the same as the version II lens's ET-155(WII) lens hood, with the paint color being the primary difference. This hood is relatively rigid, rather light (9 oz, 255g), and huge, offering the frony lens element excellent protection from bright light, impact, and the elements. While this hood is quite rugged, protect it as a replacement will cost as much as a nice lens.

Canon ET-155B Short Lens Hood for EF 400mm f/2.8L IS III USM Lens

The big lens hood is sometimes an issue from a space standpoint, including packing space and space on the sidelines or other events. For those circumstances, there is the optional Canon ET-155B Short Lens Hood. The price tag is substantial for this one also.

Canon EF 400mm f/2.8L IS III USM Lens Cap

The EF 400mm f/2.8L IS version I lens came with a large leather-like lens cap that completely covered the reversed lens hood and was held in place with a drawstring that was not really needed as these covers were challenging to get off. The version II lens cap design was a huge improvement, featuring a shallower padded nylon cover that could easily be removed with one hand by simply pulling the hook-and-loop tab. That cap could be attached with the hood in ready-to-use or reversed positions and, if the Velcro tab was pulled tight enough, it could be attached directly to the lens without the hood being there. I doubt the latter feature was designed for, but the RF and version III lens's E-180E cap formally incorporates that feature. With an overall design similar to the version II cap, the version III cap adds a less padded, more stacking, and shipping flexible nylon extension with a drawstring that snugs around the end of a non-hooded lens. The front of the lens cap is additionally padded, with a rigid interior protecting the front lens element.

Canon EF 400mm f/2.8L IS III USM Lens Strap

The included padded lens strap can be attached to the tripod ring, an attachment point that allows the camera to be rotated without the neck strap following the rotation (causing strangulation).

Canon EF 400mm f/2.8L IS III USM Lens Case LS400

There is a new Canon super-telephoto lens case. Before the EF version III lens, Canon's super-telephoto lenses came in a rigid lens trunk. These shaped, lockable trunks were nice, protective, and good for storage, stacking, and shipping purposes. However, these trunks were expensive, often far oversized, could not hold a camera body, were not especially comfortable to shoulder carry, and rarely left my studio.

New with the RF and version III telephoto lenses is a sling-style (single strap) shoulder case, the Canon LS400 Soft Lens Case, replacing the trunk.

This nylon case looks great, is relatively compact and lightweight, well-padded, easy to use with smooth-functioning zippers and large pulls, and has a round molded-plastic bottom that keeps it upright on a flat surface. A thin 7" (178mm) tall by 5" (127mm) wide zippered pocket and a pair of strap attachment points are provided on both sides of the case. The shoulder strap is padded and strong, and breathable padding is provided on the strap's case side, adding to the shoulder-carrying comfort. The convenient hand strap on top is also strong, with breathable padding ensuring that grip is not lost. Four hook-and-loop-adjustable pads are provided for interior use.

Canon EF 400mm f/2.8L IS III USM Lens Case Pads

This case is nicely sized to hold its intended cargo.

Canon EF 400mm f/2.8L IS III USM Lens Case Open

Making the case large enough for a mounted camera to fit would have been my preference. The additional cost would have been little (especially relative to the cost of the lens), and the utility of the case would have been greatly increased.

Transporting a large lens with a camera mounted increases the risk of damage, but there are many times when I'm transporting a lens such as this one in a lower-risk manner and prefer quick access to the mounted lens or want to avoid mounting a lens in unfavorable conditions. For example, arriving at a soccer (football for our friends across the pond) tournament and transporting the lens from field to field throughout the day can be low risk. Or, when photographing wildlife, getting the lens into action fast can mean the difference between getting the shot and getting nothing. For air travel or shipping, I usually separate the lens and body.

This case was designed to easily accommodate the slightly longer RF lens (the EF III is shown in the case pictured above).

The old 400C hard case weighs 9.6 lbs (4.35kg) empty, and the new LS400 weighs 2 lbs (.9kg). That is another significant weight savings.

At review time, the Think Tank Photo StreetWalker Pro is my preferred carry case for this lens.

Price, Value, Compatibility

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The Canon RF 400 F2.8 L IS USM Lens's price will wow you as much as its image quality and overall performance. Without a doubt, the price is the biggest hurdle for getting this amazing lens into the hands of photographers wanting it (which is nearly all of them).

While this lens is expensive, it is priced in line with the other camera brand options. Canon USA's Rudy Winston shared some of the reasons for the high cost of this and similar lenses:

Fluorite lens elements: fluorite is an artificially grown crystal, not glass, and requires a lot of time to grow to sizes that can be used as lens optics. [In this regard, surely some cost savings was realized with the shifted-rearward fluorite elements being smaller in size] And then, it requires incredible skill and precision to cut and grind into shape for use as an optical element.

Mechanical design: these lenses require tremendous precision, to sustain optical alignment with their physical length and to withstand the inevitable bumps and bruises that they'll get in the hands of working professionals. This is easy to take for granted, but they're much more difficult to manufacture than smaller, lighter lenses.

Skill of manpower used for assembly: usually, the most skilled and experienced workers are culled for assembly of the big white super-tele lenses (along with the Cinema EOS lenses), AND these lenses tend to be largely hand-assembled. The costs associated with this are, of course, absorbed into the final selling price of the lens.

Finally, you have simple economies of scale... even if the price was arbitrarily cut in half, we know the number of units sold per year would never match those of lighter, more everyday pro-level lenses (think of 70-200/2.8s, 24-70/2.8s, and so on). So the development costs and so on, again, have to be made up with fewer total lenses being sold during the product's lifetime.

Fortunately, quality lenses hold their value well. While the overall cost of ownership for these lenses can vary greatly (including the effects of monetary exchange rate fluctuations), a Canon super-telephoto lens can typically be sold for a solid percentage of the purchase price. The concept of buying this lens to photograph a child's high school sports career and later selling it to fund their college education seems logical. Those pursuing professional wildlife or sports photography will likely find the Canon RF 400 f/2.8L IS Lens a career requirement.

If the price makes the RF 400mm F2.8 unobtainable for you, consider renting one for your special events. If you are not shooting professionally, consider getting other parents to share in the rental expense in exchange for photos of their kids participating in sports.

As expensive as this lens is, you get what you pay for. Also, consider that price is a barrier for entry, meaning skilled photographers with this lens have a competitive advantage that will not be overcome by the masses with a camera.

As an "RF" lens, the Canon RF 400 f/2.8L IS USM Lens is compatible with all Canon EOS R-series cameras. Canon USA provides a 1-year limited warranty.

The first reviewed Canon RF 400 f/2.8L IS USM Lens was purchased online retail. That lens went to live the exciting rental life. After needing this model multple times over the next few months, I repurchased it.

Canon RF 400 f/2.8L IS Lens Compared to Canon EF 400mm f/2.8L IS III USM Lens


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Building a mount adapter into a lens does not change its image quality. That means the Canon EF 400mm f/2.8L IS III USM Lens and the Canon RF 400 f/2.8L IS Lens are equals in that regard. However, the RF mount technology increases the CIPA image stabilization assistance rating to 5.5 stops from 5.0 stops.

Canon RF 400 f/2.8L IS Lens Compared to Canon EF 400mm f/2.8L IS III USM Lens with Hoods

The Canon RF 400 F2.8 L IS Lens vs. Canon EF 400mm f/2.8L IS III USM Lens shows the RF lens slightly longer and slightly heavier. Add the Canon Mount Adapter EF-EOS R into the equation, and the reverse is true.

The EF lens can be mounted to a DSLR, while the RF lens cannot. The EF lens has a focus distance window vs. this information available only on the LCD or EVF. The two lenses are priced identically.

If you have migrated to mirrorless cameras, get the RF lens. Upgrading from an EF 400mm F2.8 III lens currently in the kit is considerably harder to justify.

Canon RF 600mm f/4.0L IS USM Lens Compared to Canon RF 400mm F2.8 L IS USM Lens

Should I get the Canon RF 600mm F4 L IS USM Lens or the Canon RF 400mm F2.8 L IS USM Lens?

Obvious and significant are that 400mm and f/2.8 are significantly wider than 600mm and f/4. Also key to this comparison is that adding the Canon RF 1.4x to the RF 400 makes it a 560mm f/4 lens, nearly equalizing the 600mm lens's primary advantage.

Canon RF 600mm f/4.0L IS III USM Lens Compared to Canon RF 400mm F2.8 L IS USM Lens with Hoods

At their wide-open apertures, these two lenses turn in nearly perfect results in the image quality comparison. At f/4, the 400mm lens is even slightly sharper. Extenders impact image quality, and with the RF 1.4x behind the RF 400mm lens, the 560mm vs. 600mm image quality comparison shows the RF 600 sharper in the center of the frame. However, the center differential is not substantial, and the two lenses compare similarly in the mid-frame and periphery.

The 400mm lens has slightly stronger pincushion distortion and slightly stronger barrel distortion at 560mm.

The Canon RF 400mm F2.8 L IS USM Lens vs. Canon RF 600mm F4 L IS USM Lens comparison shows the 400mm lens slightly lighter and considerably shorter. The RF 1.4x addition equalizes the weight but subtracts only slightly from the length difference. Natively, both lenses have .17x maximum magnification, but the RF 400 focuses considerably closer, an advantage that holds with the 1.4x mounted. The RF 400 is less expensive by a significant amount, though the percentage difference doesn't seem as great. Adding the RF 1.4x to the equation brings the two options closer.

If you need the 400mm angle of view, the choice is easy. Get the 400mm lens. With equivalent subject framing, the 400mm lens will produce the same impressive background blur as the 600mm lens at f/4, but the 1-stop lower ISO setting will produce considerably lower noise levels in low light. For wildlife, I usually take the 600mm option. When sports permit a close enough vantage point, I take the 400mm lens. Getting both lenses is the optimal solution, but that option requires a significant financial investment.

Those open to other brand cameras should consider the Sony FE 400mm f/2.8 GM OSS Lens.

Canon RF 400 F2.8 L IS USM Lens Compared to Sony FE 400mm f/2.8 GM OSS Lens

In the image quality comparison, both lenses turn in outstanding performance, but I'll give the Canon a slight advantage in this comparison. The Canon lens also has a modest image quality advantage with extenders mounted.

Canon RF 400 F2.8 L IS USM Lens Compared to Sony FE 400mm f/2.8 GM OSS Lens with Hoods

We find the two lenses having the same weight in the Canon RF 600mm F4 L IS USM Lens vs. Sony FE 600mm f/4 GM OSS Lens comparison. The Sony lens (and lens hood) is slightly smaller and has 11 aperture blades vs. 9. I find the Canon lens's image stabilization system to be more effective than the Sony's in the field. The Canon lens costs $1.00 more than the Sony lens at review time.

Use the site's comparison tools to create additional comparisons.

Canon RF 400mm F2.8 L IS USM Lens Angle View with Hood


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As I said in the EF review, the Canon RF 400 f/2.8L IS USM is an absolutely no-compromise lens created by a company with a long history of delivering the best-available camera lenses. This lens is essentially the same as the Canon EF 400mm f/2.8L IS III USM Lens. It is a roll-up of the best technology, including that in the lens's design and the innovative manufacturing techniques required to produce it.

With superb build quality, a moderately-long telephoto focal length, an ultra-wide aperture, a fast and precise AF system, outstanding image stabilization system, and extremely-high-grade image quality, the built-for-speed RF 400mm F2.8 L IS USM package works exceedingly well for discerning sports photographers, wildlife photographers, and photojournalists. In addition, this lens will have under-funded photographers digging through their gear kits in search of anything that might be considered non-essential and contributable to the RF 400mm f/2.8L IS Lens fund.

Once the investment challenge has been overcome, taking delivery of a new Canon super-telephoto lens makes even the most jaded photographer feel like a kid on Christmas morning.

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