Commenting to find later

Wow ok that changes things. Gonna have to rethink my approach now.

To add to the point above: it looks like you've got a choice between the heavy-hitting third-party primes or that super portable native wide-angle. Tbh, I'm really satisfied with how this thread breaks down the sharpness vs price debate. Just a few things to be careful with if you're chasing high performance:

• Filter compatibility: many ultra-wides can't take standard screw-on filters, which is a pain for long exposure landscapes.
• Adapter quality: if you go the DSLR lens route, make sure your adapter is rock solid or you'll get weird softness on one side.
• Distortion: don't get so wide that your mountains look like tiny pimples on the horizon. Honestly, I've found that the best lens is the one that doesn't make you want to quit hiking halfway up a trail. I'm happy with a setup that balances weight and optics... no complaints here as long as the corners stay clean.

Wait really?? Thats actually super helpful. I always thought it was the other way around.

I'd suggest the Sigma 14mm f/1.8 DG HSM Art. Sharpness is phenomenal; watch for distortion.

For landscapes on the R5 II, consider the Sigma 14mm f/1.8 DG HSM Art. Its sagittal coma flare performance is impressive for nightscapes. Edge distortion is present, but correctable in post. Have you considered a good rectilinear lens too? Might suit your needs better.

Landscapes, eh? Forget the hype. Over the years, I've learned build quality matters. Sigma Art series gives Canon's L glass a run for its money. Check MTF charts; Sigma's sharpness is often comparable, sometimes better. You can snag a used Sigma 14-24mm f/2.8 for around $1200. Resale value is decent too.

Before dropping $1500, consider renting a Canon RF 16mm f/2.8. See if ultra-wide truly fits your landscape style first. I wasted money on lenses I barely used – learn from my mistakes!

Be careful on roadsides! Sigma 14mm might work; make sure to stay visible.