We review the Canon RF 100-400mm f/5.6-8 IS USM, an affordable telephoto zoom lens

If you need a versatile telephoto lens, there aren’t many choices for the RF mount. Unless you are using the EF-RF adapter, there are only two options available, the RF 100-500mm or the RF 100-400mm. Is the much cheaper RF 100-400mm a good choice?

Did you switch from Canon DSLR to Canon mirrorless? In this case you probably have a selection of EF lenses available, perhaps lenses made by other manufacturers like Sigma or Tamron. There is no problem using these lenses with the EF-RF adapter on Canon mirrorless cameras.

If you want to skip the EF-RF adapter, you are forced to buy Canon lenses. After all, other manufacturers are not allowed to produce RF lenses with autofocus to date. So if you like to use a telephoto lens like a 100-400mm, the options available are limited to say the least.

The Canon RF 100-500mm f4.5-7.1L IS USM is an amazing lens. It’s big, heavy and very expensive. If you can save some money, I would definitely recommend the lens. That said, I can also imagine that it’s not a goal that everyone can afford. So you need an alternative.

The RF 100-400mm f/5.6-8 IS USM

Fortunately, Canon has released the RF100-400mm f/5.6-8 IS USM. It’s a much smaller, lighter and much, much cheaper lens. You can easily buy four of these lenses for the price of a single RF 100-500mm lens.

If a lens is much cheaper than its bigger brother, how does it perform? Since it’s not an L lens, you might expect its performance to be less. Still, it has to be a good lens, because Canon can’t afford it to be just a mediocre lens. Canon Netherlands provided me with the RF 100-400mm f/5.6-8 IS USM for review.


The RF 100-400mm f/5.6-8 IS USM is a small lens just 16.5 centimeters long. Its weight is 635 grams, which makes it easy to take with you. The lens extends when zoomed to 400mm. It will increase in length by 7.6 centimeters. Because the weight is kept mostly close to the camera, it won’t be too unbalanced when zooming in. The lens does not have a tripod collar available, something to keep in mind if using the lens on a tripod.

The zoom ring is large and rotates smoothly. Its diameter increases towards the front end of the lens, making it easy to find without looking. The focus ring is placed in front of the zoom ring and has a finer texture. Finally, the control ring is placed on the front of the lens barrel.

Three switches are available. The lock switch locks the zoom mechanism at a focal length of 100mm, preventing unwanted extension of the lens barrel. The other switches offer the option of disabling image stabilization or autofocus. There is no focus limiter or different stabilization setting available.

The lens is made from a good quality plastic and seems quite sturdy. It lacks waterproofing, which is a shame. Because it’s not an L lens, there’s also no lens hood or pouch in the box.

Image stabilization and aperture

Image stabilization is rated up to 5.5 stops. This can make a big difference to using a lens with a focal length in this range. Theoretically, image stabilization will allow you to shoot at a shutter speed of 1/15s, provided the subject allows it.

Combining the 100-400mm RF lens with a camera that has built-in image stabilization will only increase the rating by half a stop to six stops, which isn’t that much.

The maximum aperture of the lens ranges from f/5.6 to f/8. It might not sound ideal, but if you compare the values ​​with the RF 100-500mm lens, the difference isn’t that big. However, you may need to increase the ISO if a faster shutter speed is important. If not, you can rely on image stabilization.


One of the main advantages of this lens is its size and weight. It’s easy to take the lens with you. Just put it in your bag or on your camera and go. The focal range makes it a versatile lens for many types of photography.

If you like photographing animals, this is an ideal lens. I noticed that the minimum focusing distance of 88 centimeters at 400 mm works perfectly for semi-macro. It allows a maximum magnification of 0.41x, ideal for flowers and insects, among other small things.

It is however wise to keep an eye on the shutter speed. Especially when there’s not much light available, it’s easy to rely on image stabilization too much. It may be necessary to regularly use a high ISO setting for this lens. Given that most EOS R cameras perform reasonably well at high ISO levels, this shouldn’t be a problem.

Image quality

Being such a cheap lens, especially compared to its big brother, the RF100-500mm L lens, I was surprised at the quality of the images. There is some cushioning at 400mm and vignetting is close to two stops at the corners.

Since most people will have automatic lens correction enabled in the camera, most lens flaws will be corrected. Actual results will look good, and may even be close to the quality you find with the RF 100-500mm L lens. That’s only if you compare it side-by-side in a controlled situation the difference in quality will become more apparent. But who does that in real life?

Use with a teleconverter

Although the RF 100-500mm L lens can be used with a teleconverter, it is not really designed for this purpose. The focal range will be much limited, allowing zooming only at the longer end. On the other hand, the RF 100-400mm is fully compatible with 1.4x and 2.0x teleconverters. This increases the focal length range to 160-640mm or 200-800mm, depending on the teleconverter you choose.

The downside is the reduced maximum aperture you end up with. If f/5.6-8 bothers you, f/8-f/11 with the 1.4x teleconverter or f/11-f/16 with the 2x teleconverter certainly will. If you don’t mind the smaller aperture, you should realize that there is also the problem of diffraction with these small apertures, especially with high resolution cameras like the Canon EOS R5.

If you need those long focal lengths, maybe the RF 600mm f/11 or RF 800mm f/11 lens can be an alternative, or you can choose one of the two APS-C mirrorless cameras that Canon has launched. Using the RF 100-400mm on these bodies will provide a nice increase in magnification without the problem of an even smaller aperture.

My conclusion

Although the image quality is lower than the more expensive RF 100-500mm L lens, the difference is not that great. Maybe if you compare the pictures side by side it will be visible. There’s also the longer zoom range in the more expensive of the two, of course, and the wider maximum aperture. Again, the difference is only marginal.

The RF 100-500mm L lens has better construction, better sealing and the tripod collar. This can make the difference when using the lens in harsh weather conditions. In addition, the speed of autofocus, together with the focus limiter and the various image stabilization options, will make the RF 100-500mm L lens a good choice for those who need a lot control. But it’s a pretty expensive lens, out of reach for many photography enthusiasts.

Considering the price, the RF100-400mm f/5.6-8 IS USM is probably the best choice for many. The image quality is very good. It won’t match the big brother, but it does come close. Finally, the weight and size of the RF 100-400mm make it a great lens to have and take with you.

What I like

  • Height and weight
  • 5.5 stops image stabilization
  • Good image quality and sharpness
  • Can be used with 1.4x and 2.0x teleconverters
  • Closest focusing distance and 0.41x magnification
  • Price

What could be improved

  • Not so sensitive to light
  • No tripod collar possible
  • Closing the aperture will cause diffraction
  • No sealing
  • Sun visor not included


There is no alternative available at this time. If you are ok with using an adapter, any lens with an EF mount can be used. In this case, any EF lens with an adapter is always a good option, with plenty of lenses to choose from. Nevertheless, I can recommend the RF 100-400mm f/5.6-8 IS USM, as it is a very nice lens at an affordable price.

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