Canon RF 100-500mm F4.5-7.1 L IS USM Review: Big Mistake or Best Lens I’ve Ever Owned?

In January 2025, I purchased the Canon RF 100-500mm f4.5-7.1 L IS USM lens as my main wildlife photography lens. I had just upgraded my camera body to a Canon R6 Mk II and read mixed reviews about whether my Sigma 150-600mm would perform well, especially in terms of autofocus. Since quick focus is crucial for wildlife shots and I didn’t want to risk subpar performance, I decided to trade in the Sigma.

Before buying the 100-500, I considered other options like the EF 100-400mm f/4.5-5.6L IS II USM with an EF to RF adapter and the Canon RF 100-400mm f/5.6-8 IS USM. Not knowing how the EF lens would perform with the adapter, I decided against it. The lightweight, compact design and budget-friendly price of the RF 100-400mm were definitely tempting. Going from 600mm to 500mm already meant losing reach, and switching from APS-C to full-frame meant losing the 1.6x crop factor too. My gut told me I’d regret giving up that much reach, and having owned a Canon L lens before, I hoped the RF 100-500mm f/4.5-7.1 L IS USM would be worth the investment.

I’ve been using this lens for over a year now, and I absolutely love it with zero regrets about my purchase. The autofocus is lightning-fast and accurate, and at just 3 pounds, it’s still light enough to carry comfortably on hikes. The versatility of a zoom lens is unbeatable; 500 mm gives me plenty of reach, and being able to zoom out for more environmental shots, especially of larger mammals, is something you just can’t get with a much pricier prime lens. Shooting at 100 mm on a full-frame camera has also given me some landscape shots I’m really proud of, which wouldn’t have been possible with my 150-600 on a crop sensor body.

Some negative feedback I’ve seen about the 100-500 is that it’s too slow in terms of aperture at f/7.1 when zoomed to 500mm. Personally, on a full-frame camera, I haven’t found this to be a problem in low light. I’m perfectly fine using ISO 2000 as a starting point and increasing it to get a fast enough shutter speed. Would this be an issue on a crop sensor camera, perhaps, but for me it’s a moot point. Of course, a wider aperture and shallower depth of field would be great, but that would also come with a much steeper price tag, probably double, and far beyond my budget. If Canon released a 100-500mm f/4 fixed aperture lens tomorrow, I wonder how many of the complainers would actually open their wallets and buy one, or if their demands are just imaginary. Unless you have a steady income from photography, I think such a lens is beyond the budget of most hobbyists. 

As many of you know, I do much of my photography during the summer months from a Swift 14 foot Prospector pack boat, so the weather sealing on the 100-500 is a great feature, giving me peace of mind if water drips from my paddle or I get caught in a sudden downpour. This past winter, I spent a lot of time photographing moose, foxes, and wolves in the snow, and once again, the weather sealing proved invaluable when a sudden squall rolled in.

Like most lenses, the 100-500 is sharper when stopped down, so when light allows, I prefer to shoot at f/8; still, it’s plenty sharp wide open. This lightweight lens is a joy to carry all day, and I can handhold it much more easily than my Sigma, which I often struggled with. Combined with the easy handling and the excellent high ISO performance of my R6 MK II, I’ve captured low-light shots I never could have managed before.  

The only drawback I can think of for this lens might be the price. Is that really a drawback, considering everything seems overpriced these days? Coming in at just under $4000 before tax, this lens certainly isn’t cheap, but if it’s in your budget it’s a great choice. All in all, I think anyone who picks up this lens will be more than satisfied with how it performs.

Having owned several telephoto zoom lenses over the years from Sigma, Tamron, and even another Canon L lens, I can honestly say the 100-500 is the best lens I’ve ever used. Whether you shoot full-frame or not, the Canon 100-500 is a fantastic choice. There are slightly cheaper alternatives, like the Canon 200-800mm f/6.3-9.0 IS USM, but it’s 1.5 pounds heavier and lacks the high-quality weather sealing of Canon’s L series. If you are in the 100-500 is too slow at f/7.1 camp, you definitely won’t like f/9.0. For a more budget-friendly and lightweight option, the Canon RF 100-400mm f/5.6-8 IS USM also comes highly recommended.

If you’re considering the Canon RF 100-500mm f/4.5-7.1 L IS USM lens and it’s within your budget, I’d say go for it. It’s honestly the best lens I’ve ever owned. If you want more reach, the Canon 200-800mm f/6.3-9.0 IS USM might be the one for you, though for me, the extra 1.5 pounds was a dealbreaker. The Canon RF 100-400mm f/5.6-8 IS USM caught my attention with its lightweight design and attractive price, but in the end, the lack of reach and weather sealing turned me away.

If I had to do it all over again, I’d buy this lens again in a heartbeat with no hesitation or regrets. If you are in the market for a telephoto zoom and are looking at Canon, the Canon RF 100-500mm f4.5-7.1 L IS USM lens is simply awesome! 

Good birding,
Paul  

My Gear 

• Camera: Canon EOS R6 Mark II 
• Main wildlife lens: Canon RF 100-500mm F4.5-7.1L is USM
• Camera Harness: Cotton Carrier CCS G3 Single Camera Strap System
• Binoculars: Vortex Vanquish HD 10 x 42 

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