1. Last year I had the opportunity to shoot the IMSA Battle On The Bricks at the Indianapolis Motor Speedway from the observation deck/roof of the BMW Performance Center on the track.  The only lens I had available was my Canon RF 70-200 mated to my Canon R5.  In short, it wasn’t enough lens.  Not that I didn’t come away with some great shots…I just had to crop the snot out the images I got.  I had a great time, and knew I wanted to go back for the 2025 IMSA Battle On The Bricks – and I knew I’d bring some longer lenses.

Fast forward to early 2025 and I decided I put in a request to Canon Professional Services to borrow some lenses…about $26,000.00 worth.  One of these lenses was the Canon RF 100-300 f2.8.  The RF 100-300 f2.8 is one of the first full-frame RF zooms to pair a long telephoto range with a constant f/2.8 aperture across that span, a combination normally reserved for prime lenses or “super zoom / super tele” special designs. It clearly targets professionals (or very deep-pocketed enthusiasts) working in sports, events, motorsports, wildlife (especially in moderate distances), red carpet, airport, and other high action / low light arenas.  Given its price (roughly ~$10,00 as of this writing)  and size, it’s not for casual use — you buy this lens because you need or can exploit what it offers.  Canon positions it partly as a replacement (or alternative) to the venerable EF 300mm f/2.8 prime, and potentially consolidates multiple lenses into one package (70-200 + 300, etc.), especially with teleconverters.

Let’s get this out of the way right now – this lens is large and heavy.  Perhaps unsurprising given its specs, but it still surprised me just how big and unwieldy this lens really is as compared to the RF 70-200 f2.8.  In fact, at the time I was testing this lens, I was also testing the Canon RF 400mm f2.8 prime – the 100-300 was only slightly smaller and lighter.  In researching the lens, I found that most reviewers compare its footprint and weight to the older EF 300mm f/2.8 prime, noting it’s somewhat larger and heavier due to the added zoom mechanics.  The lens length is about 323 mm (12.7 in) and the diameter is 128mm (~5″) which is substantial.  Because of its bulk, extended handheld use is tiring; monopods, gimbals, or tripods are natural companions.  Fortunately, I brought both tripods and monopods to Indy for my testing.  In summary, this lens is robust, professional, but heavy and demanding in handling.

The optical performance of this lens is however stellar.  In my testing, I found At 300mm, images remains impressively sharp even at f/2.8, with minimal softening toward the corners:

Truth be told, from the position I was shooting, 300mm was still a bit shy of ideal focal length.  I got better images with my EF 100-400 f4.5 – f5.6 from the position I was shooting these images.  I do wish I would have had the opportunity to us the lens at one of the Friday night varsity high school football games I’ve been shooting as of late – I think it would have been a much better test of the lens.  Still, I was not unimpressed with the image quality this lens produced with both the Canon R1 and R5 Mark II I was shooting with that day.

Admittedly, with everything I had read about this lens, I was prepared to be positively blown away when using it.  Except…I wasn’t.  Not that the performance isn’t fantastic.  My issue is that you can do nearly as well for far less cost in terms of both size/weight, as well as dollars.  Let’s say you’re NOT a pro sports photographer who is being supplied this lens by the outlet you represent…or can’t pay for the lens in a few short weeks as a freelance pro shooter.  Maybe you’re a working professional without deep pockets (keep in mind the average pro photographer makes between $40k and $60k per year according to recent data).  Or even an enthusiast.  If you HAVE to have f2.8 because of available light, then you can pick up a Canon EF 300mm f2.8 II for under $4000.00 pre-owned.  That will provide you VERY comparable image quality and auto focus performance when using the Canon EF to RF adaptor.  If you’re shooting in brighter lighting conditions, the Canon EF 100-400 f4.5-f5.6 II will also provide very comparable image quality with more focal length range at less than $2000.00 preowned.  In other words, You could buy a couple of R6 Mark II’s, an RF70-200 f2.8, and either of the two above mentioned EF lenses for about the cost of the RF 100-300 f2.8.  Food for thought.

The Canon RF 100-300mm f/2.8 L IS USM is one of those lenses that’s easy to love if you need what it offers. It delivers optical performance that often meets or exceeds expectations for a zoom of this magnitude — and in some respects even rivals primes. If you shoot action, sports, motorsports, or events professionally (or semi-pro) and your workflow involves long focal lengths, then this lens has the potential to be a kit consolidator: fewer lens swaps, more versatility, less downtime.  However, it’s not for everyone. The size, weight, ergonomics, and cost are all real barriers. If you don’t need absolute top-tier long telephoto performance.  I’m not in the unique subset that absolutely requires what this lens has to offer…though perhaps after shooting with this lens, I wish I were.