RF 14-35mm f/4L maybe, but a bit expensive than your budget.

Honestly, for $1200, you have to be really careful about whether you want native RF glass or if you're willing to adapt older EF gear. A big mistake I see people make with landscape and architecture is prioritizing the widest possible focal length while totally ignoring edge-to-edge sharpness. If you go too cheap on a budget zoom, those architectural lines will look like a barrel-distorted mess and you'll spend forever in post trying to fix it. Also... don't get too hung up on needing f/2.8. Like, for architecture and landscapes, you’re basically always stopped down to f/8 or f/11 on a tripod anyway, so paying a premium for a fast aperture is usually a waste of your budget. I mean, I'd suggest looking at some of the higher-end prime lenses if you want to stay under that firm $1200 limit without sacrificing resolution. Just watch out for heavy vignetting on some of the more compact wide-angle options; sometimes the digital lens corrections required can really eat into your final image quality more than you'd expect.

Yeah, I totally agree that focusing on edge-to-edge quality over just getting the widest focal length is the smart move, especially for architecture. To add a small point to that, since you mentioned landscapes, I’d really look at the overall reliability and weather sealing before you commit. When you're shooting outdoors, peace of mind is *everything*. Here's what I look for to ensure a lens won't let me down in the field:
- High-quality weather gaskets to keep dust and moisture away from your R6 sensor
- A solid, metal-based mount for long-term durability
- Reliable internal focus mechanisms that don't feel flimsy Honestly, I've learned the hard way that a cheaper lens isn't much of a deal if it fails during a trip. Making sure the build quality is up to par for field use is just as important as the glass itself.

Stumbled upon this discussion and wanted to chime in... one thing Id ask first is whether you're usually using a tripod or if you're planning on shooting these handheld? It really changes the priority for stabilization and how I'd weigh my options. Personally, I'm pretty conservative when it comes to gear reliability. If you want something that is tried and true, the Canon EF 16-35mm f/4L IS USM with the Canon Mount Adapter EF-EOS R is almost impossible to beat for the price. It's a professional-grade workhorse and very sharp for architecture. I've used that combo for ages and it just wont let you down. If you're dead set on native glass and can't find a deal on the L-series, the Canon RF 15-30mm f/4.5-6.3 IS STM is an option, but honestly it feels a bit more consumer-grade. If it were my money, I'd stick with the EF L glass or wait for a refurbished Canon RF 14-35mm f/4L IS USM to pop up on the official store... they often hit that $1100 mark during sales.

My buddy told me the exact same thing last week. Guess he was right lol.

Agreeing with the point about edge-to-edge sharpness being the priority here. If you're doing architecture on the R6 Mark II, you really cant afford those soft corners. Just be careful with older zoom designs... they often have way more field curvature than the modern stuff. If you're tech-savvy, you can actually calibrate for some of that using custom lens profiles in post-processing, but it's a bit of a DIY rabbit hole. Make sure to check the decentering on any copy you buy by shooting a flat brick wall first. It's the easiest way to see if the internal elements are still aligned properly after years of use.

I've spent a lot of years shooting buildings and one thing I've learned the hard way is that not all wide-angles are created equal when it comes to straight lines. I used to rely on older EF glass, but the balance on the R6 II can feel a bit off with the adapter sometimes. I would suggest being very careful with the cheaper RF consumer zooms if architecture is a major priority because the digital distortion correction can really eat into your resolution at the edges. In my experience, you might want to consider looking for a used Sigma 14-24mm f/2.8 DG HSM Art for Canon EF. I used that lens for a long time before switching fully to native RF glass, and its edge-to-edge performance is honestly better than many L lenses in that price bracket. If you're dead set on staying native and under budget, the Canon RF 15-30mm f/4.5-6.3 IS STM is an option, but you'll need to be mindful of the slower aperture for any low-light work. It's a bit of a trade-off between weight and light gathering... just make sure to weigh those priorities before pulling the trigger. I've found that saving a few bucks now usually costs me more later when I inevitably trade up anyway.