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The Simple Review: Canon RF 100-400mm F5.6-8 IS USM...Should You Get It?

Updated: Jan 10

It's no secret that photography gear can be expensive, but sometimes we can get a really great piece of gear without the heavy price tag. That is exactly what the Canon RF 100-400mm F5.6-8 IS USM is.

This lens clocks in around $500 and may even be less than that if you catch it on sale. Don't let the low price fool you though, this lens is sharp, clear, and extremely versatile if you are in the market for a 100-400mm lens that won't break the bank. Now in all fairness compared to the big brother of this lens the Canon RF 100-500mm F4.5-7.1 L IS USM, the lens featured in this review has some things to be desired after. Now that we have some well-managed expectations let's start breaking down this lens simply.

The Pros

As I mentioned above, one of the largest pros to this lens is the price so I won't highlight that anymore, instead, I want to break down all of the reasons I would grab this lens when I leave for a shoot.

1. Image Stabilization

The Canon RF 100-400mm F5.6-8 IS USM comes equipped with image stabilization which is really handy for the longer zoom range. If you are not familiar with the importance of image stabilization, this simply means it will be easier to capture sharp images at slower shutter speeds. Having image stabilization on a lens at this price point is amazing and truly allows you to focus on capturing the world in front of you.

Now in my testing of this feature with the Canon EOS R and Canon EOS R6, I have found that it is important to stay within 1/50th of a second to get a good image. Sadly, most subjects that I have been photographing move too fast to even stop the motion at that slow of a shutter speed. Speaking honestly, there is no reason to go that slow with this lens in a practical sense. The slowest I have gone photographing animals, kids running and dancers on stage has been 1/150th of a second. The image stabilization works great for this shutter speed.

2. Sharpness

Next on the list is sharpness. Needless to say that you want a lens to be sharp. This lens does not disappoint. In my testing and everyday use of this lens, I found that my keeper rate of images was at least 96%. I think this was due to the great autofocus system of the EOS R cameras, but the lens was able to keep up.

Now there is some softness in the corners of the image, but if you crop or post-produce your image in any way, there is no need to even talk about this issue because the average user will not notice. The center of the image is really sharp and has great contrast. I wouldn't photograph directly into a light source with this image, but you will get great results photographing well-lit subjects.

It is fair to note that this lens is not as sharp when you shoot at high ISOs. In my testing when I go above 6400 ISO, the lens gets a little soft. The images captured at f8 are come out great and are very useable.

3. Weight

One of the largest issues with telephoto lenses is their weight. This lens is not heavy at all and can be carried for long periods of time. I took this lens with me on a 3-hour photo walk/hike and never had any issues with the weight of the lens. It was attached to my EOS R6 and I used a single-point camera sling for the entire walk. At no point was my shoulder tired of the combined weight of the camera and lens. So if you are concerned about picking up this lens because a telephoto lens is typically too heavy to carry around. I am happy to report this lens travels just fine on long walks and hikes as long as you can get over the length of the lens which is discussed in the cons.

The Cons

The old saying, "You get what you pay for" comes to mind when I start to think about the cons of this lens. No means are they impossible to overcome, but I want to be as fair as I can in this review so I will be real with you on the list of cons I have for this lens. To be honest, though, there are really on two cons in my book.

1. The variable aperture

There is nothing more annoying than seeing the image you want to capture and realizing that to get it, you have to compromise on your exposure settings. Now with the Canon EOS R6, you can get useable images at high ISOs, so you compromise there but when you don't even get a choice with your aperture, you can get a little frustrated.

If you are not familiar with the term variable aperture, as you zoom this lens the aperture will change without your permission resulting in a darker image if not compensated for in either your shutter speed or ISO. This means your exposure is going to change if you are using full manual. Adjusting for the loss of light as you zoom is not hard, especially if you are using flash or modifiable light, but for the times when you are at the basketball game sitting on the sidelines and the only way to frame up the shot is to zoom, this lens will cramp your style hard.

2. Telescoping front element

If you want to be discrete while photographing, this is not the lens for that. The front end of this lens extends as you zoom and can be distracting to those around you. This is only an issue when I am working in tight spaces like plays, concerts and home parties ect. When I am outdoors this is a non-factor. This is a common occurrence on lower-end lenses so I am not surprised it is there.

I will note that since the front element extends, you have a higher chance of breaking the lens if you hit something. So you have to be mindful and careful.


I recommend this lens for the average photographer or anyone that needs a little extra reach at a low price point. This lens handles well and performs great. For the price and the RF system, there is not another lens on the market like it and is the reason why I think it does so well.

I am curious to hear your thoughts on this lens, do you think that the Canon RF 100-400mm F5.6-8 IS USM is worth it? Let me know in the comments.

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