Canon RF 1.4x Extender Review

Canon RF 1.4x Extender

The new Canon RF 1.4x Extender is expected on the streets in late July. I will complete this review when the lens arrives. In the meantime, here are my expectations.

Do you need focal lengths longer than those natively available in your current Canon RF telephoto lens? If the lens is compatible with extenders, adding a Canon RF 1.4x extender will provide a significant focal length increase.

Canon RF 1.4x and 2x Extender Comparison

What is a 1.4x extender?

A 1.4x extender is a small lens that mounts between a compatible lens and a camera, increasing the focal length or focal length range of the lens by a factor of 1.4x. This is a very noticeable amount, narrowing the angle of view significantly. For example, with a 1.4x behind it, a 100-500mm lens becomes a 420-700mm lens. It is not hard to be impressed by those numbers.

Wait, you just noticed that my math is not correct. Right, this is new math. I wanted to point out that at least one of the first RF lenses supporting extenders is only compatible at focal lengths longer than a specified length, 300mm in this case. Using 300mm for the math at the wide end makes the resulting numbers work.

Canon RF 100-500mm F4.5-7.1 L IS USM Lens with Extender

Traditionally, lenses indicated compatible with extenders were compatible over the entirity of their focal length range.

From a functionality standpoint, extenders change little. With an extender mounted behind it, a lens's native minimum focus distance remains the same, and the maximum magnification spec is increased by the extender's magnification factor. With an extender mounted, lenses continue to support IS (Image Stabilization) if that feature is present in the lens. Canon cameras continue to function as normal with an extender installed, including providing autofocus and autoexposure support.

Canon RF 1.4x and 2x Extender Side Comparison

Compatibility Matters

Canon explicitly indicates which of their RF lenses are compatible with their extenders. With lens elements protruding from the front of the primary lens barrel, Canon and most other brand extenders do not fit behind a non-compatible lens. This physical limitation also prevents extenders from being stacked (without a workaround such as an adequately-long extension tube mounted between them), and it prevents a standard camera body cap from being used on the extender.

What are the advantages of a 1.4x extender?

The sole advantage provided by an extender is the substantial focal length increase it provides, magnifying the subject, a benefit worth all of the disadvantages I'll share later in this review. Here is an example of the focal length increase provided by 1.4x and 2x extenders (Canon RF extenders were not used for this illustration).

Canon extender Comparison Image

The difference in framing (angle of view) is quite noticeable between the three images shown. Again, the focal length increase is the lone significant advantage provided by extenders.

What are the disadvantages of a 1.4x extender?

The focal length increase numbers are very attractive, but there are costs to be paid for this feature, and this list is a bit longer than the list of advantages.

I'll bullet this list for quick reading and then will discuss the points. Here is the list of extender disadvantages:

  • Existing lens optical shortcomings, including lateral chromatic aberration, are magnified with sharpness (resolution and contrast) often being negatively impacted.
  • Increasing the lens element count further decreases contrast.
  • Additional lateral CA and geometric distortion can be introduced.
  • The lens's native maximum aperture is reduced by 1- and 2-stops for 1.4x and 2.0x extenders respectively.
  • The AF speed is slowed, sometimes by a noticeable amount.
  • The overall size is increased.
  • The overall weight is increased
  • The overall cost is increased.

Universally true is that when magnifying the image transmitted by a lens, the aberrations are magnified and, along with the effect of seven additional lens elements for light to pass through for this specific extender, at least somewhat-reduced image quality is expected. Decreased sharpness (resolution and contrast) is often noticeable. While none of us want to sacrifice image quality, I expect the impact from the RF 1.4x to be minor.

Along with optimized coatings, "The extender features high-refraction, low-dispersion glass to control curvature of field and chromatic aberration of magnification for the highest image quality." [Canon]

Because extender-compatible lenses vary in their native optical capabilities, the suitability of the results captured with extenders differs greatly. Planned is for this site's Image Comparison Tool will have with-extender results for all extender-compatible Canon RF lenses. An optically excellent lens should be selected for evaluation of the optical performance of an extender. For most of us, the disadvantage second only to the image quality degradation is the loss of 1 stop of maximum aperture. The aperture value (f-stop) is the ratio of the focal length to the diameter of the entrance pupil. Increase the focal length(s) without increasing the width of the entrance pupil, and the lens will have a narrower maximum aperture.

Fast lenses are especially advantaged when using extenders. An f/2.8 lens with a 1.4x mounted behind it becomes a relatively-fast f/4 lens. An f/4 lens with a 1.4x mounted behind it becomes an f/5.6 lens. An f/4.5-5.6 lens with a 1.4x mounted behind it becomes a slow f/6.3-8 lens.

Autofocus performance can be reduced with an extender in use, but the with and without 1.4x difference is usually minor under reasonable light conditions. Low light levels increase the autofocus challenge, and the narrower aperture presented by the 1.4x extender can increase hunting in such conditions.

Three remaining facts are that extenders increase the in-use size of the lens, extenders increase the in-use weight of the lens, and extenders have a cost.

I'll address the two minor facts first. The Canon RF 1.4x Extender is impressively small and light, increasing the overall lens length by only 0.80" (20.3mm).

The mounted extender shifts the lens weight forward slightly for a tiny change of balance. Zoom and focus rings also shift away from the camera body very slightly.

Canon extenders are expensive relative to the rest of the class. Still, the cost of Canon extenders is considerably less than the cost of the lens required to gain the target focal length natively (if it exists).

Canon RF 1.4x Extender

Build Quality

The Canon RF 1.4x Extender features a brand new 7 elements in 4 groups optical design. The mounted measurements are 2.80 x 0.80" (71.2 x 20.3mm) mounted, slightly shorter than Canon EF 1.4x III Extender's 2.83 x 1.07" (72 x 27.2mm) dimensions. It's overall length is (40.7mm) The RF 1.4x weighs 7.9 oz (225g), the same as the EF III.

Canon shares: "Designed to perform in extremes, the exterior is coated in the same white heat shield coating as used on the RF 100-500mm F4.5-7.1L IS USM and RF 70-200mm lens to prevent deterioration in performance in high temperatures." and "No compromise construction, designed for reliability and durability [snip] for use by professionals and high-end amateurs."

The Canon RF 1.4x Extender's high-quality construction includes weather sealing, extending the protection similarly-featured lenses have. The Canon extenders have protective rubber around the front element to protect the extender and the lens from misalignment while mounting.

The RF 1.4x Extender comes with the Canon Lens Case LP811, a reasonable quality drawstring pouch that is only padded on the bottom.

As an "RF" lens, the Canon RF 1.4x extender is compatible with all Canon RF-mount cameras, the R-Series models as of review time. Only specified RF lenses are compatible, with notably the Canon RF 70-200mm F2.8 L IS USM Lens missing from the list. This lens was designed for ultimate compactness and that design resulted in a lack of sufficient space behind the rear lens element.

Canon provides a 1-year limited warranty.

Canon RF 1.4x Extender Side


Buying an extender over a longer lens for financial reasons can make sense. The very long focal length lenses are considerably more expensive than extenders. Using extenders to save space (vs. carrying a second, larger lens) when traveling or hiking can be a good decision. Utilizing an extender to reach a focal length that does not exist natively is a great idea.

Sports and wildlife photographers often need longer focal lengths, and these are two of the groups most commonly utilizing extenders. Photojournalism, law enforcement, and many other types of photography can utilize extenders.

I always prefer to use a lens with my desired focal length natively available, but the image quality impact from the RF 1.4x should be light. I expect to often have the Canon RF 1.4x Extender with me, and expect to use it often.

The Canon RF 1.4x Extender is a small and light addition to your kit, a moderate hit on your wallet, and in terms of versatility and capability increase, it should be a big hit to have in the gear bag.

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My Recommended Canon RF 1.4x Extender Retailers

Where you buy your gear matters. You expect to get what you ordered, and you want to pay a low price for it. The retailers I recommend below are the ones I trust for my purchases. Get your Canon RF 1.4x Extender now from:

B&H Photo
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