Best RF mount telephoto lens for sports?

Ok so, I’m still pretty new to this, but high school gym lighting is honestly the worst thing ever. Tbh, I'm not sure if that 100-400mm you mentioned will be bright enough for indoor games? Before I give full advice, are you okay with using an adapter for older EF lenses? You can save a lot of money that way if you're trying to stay under $4000. Here are some practical options I’ve seen that might work: * Canon RF 70-200mm f/2.8L IS USM: This is basically the gold standard for basketball. The f/2.8 aperture is a lifesaver when the gym lights are dim. It’s around $2,700, so it fits your budget easily. * Canon RF 100-500mm f/4.5-7.1L IS USM: This has much better reach for football than the 70-200mm. It’s about $2,800, but it might be a bit "slow" for those late-night indoor games. * Canon Control Ring Mount Adapter EF-EOS R: Getting this lets you use older EF glass, which is usually way cheaper for sports. I’ve heard the RF 70-200mm doesn't work with extenders though, so that's something to keep in mind for football reach. What kind of lighting does the stadium have?

Saw this earlier today but just getting a chance to weigh in. Honestly, I've been pretty disappointed with the current RF telephoto lineup for high school night games. The Canon RF 100-400mm f/5.6-8 IS USM is basically useless in a dark gym, and even the high-end Canon RF 100-500mm f/4.5-7.1 L IS USM is a letdown once those stadium lights come on and you're forced to crank the ISO. If you want to actually nail those shots with your R5, youre gonna need f/2.8. Unfortunately, that makes your $4000 budget tricky for a lens that does it all.

• The Canon RF 70-200mm f/2.8 L IS USM is phenomenal for basketball, but you'll find it really lacking for football unless the action is right in front of you.
• I actually went back to using an adapted Sigma 120-300mm f/2.8 DG OS HSM Sports for these exact scenarios. Its heavy as hell and the AF isnt quite as snappy as native RF glass, but it gives you that 300mm reach at f/2.8 which is a total lifesaver for night games.
• Another option is finding a used Canon EF 300mm f/2.8L IS II USM. It kinda sucks having to use an adapter on a modern body like the R5, but the glass quality is still way better for sports than the darker RF zooms. Trying to find one lens for both indoor and outdoor sports under 4k is honestly frustrating... you usually end up compromising on either reach or light and regretting it later.

For sports where you need serious reach, the Canon RF 200-800mm offers an exceptionally long 800mm reach in a relatively compact, handholdably light, weather-sealed body with good image quality, Nano USM AF, and high-performing Image Stabilization. Sports photography involves photographing subjects in motion, and stopping action with this lens's narrow apertures means high ISO settings after the sun sets, but for daytime outdoor sports, the reach is incredible. Perfect for football, baseball, or track and field where you're far from the action.

Basically, I totally agree about needing f/2.8 for those gyms; the lighting is usually garbage and you'll struggle with anything slower. From a reliability-first perspective though, you gotta consider a few more things: - Internal zoom: Lenses that dont extend are way more durable on a crowded sideline and generally have much better weather sealing for rainy football games.
- Weight balance: Since youre on an R5, look for something that keeps the center of gravity consistent so you dont fatigue your wrist or risk a drop during a long game. Honestly, build quality is just as important as the glass when youre working in those rough high school environments.

Bump - same question here