> i found the RF 14-35mm f4 and the 15-35mm f2.8 but the price gap is huge. Caught this a bit late but I actually had a pretty disappointing experience with the Canon RF 14-35mm f/4L IS USM last summer. Everyone told me the distortion correction was no big deal, but unfortunately it really bothered me how much the R6 has to stretch the corners to make the image look normal. You actually lose a bit of your field of view because of that software crop... basically felt like I wasnt actually getting a true 14mm shot when it was all said and done. I ended up feeling much safer going back to the Canon EF 16-35mm f/4L IS USM with the adapter. It is an older lens but the optical quality is just so reliable and it doesnt rely on software magic to look decent. If you are worried about those L lens standards, the EF glass is a solid bet and saves you tons of money for your trip. Glacier is amazing tho... just make sure you have extra batteries because the cold air up there drains them fast.

So i actually went through this exact same dilemma when i did a big hike in the Cascades last year. Obsessing over the MTF charts and worrying about how the R6 sensor handles the heavy digital correction on the wider end took up way too much of my time. Ngl i spent like three weeks looking at raw samples to see if the corner stretching actually ruined the pixel integrity. Here is what i found from dragging my gear through the mud and cold:

• Weight is a massive factor for reliability on the trail. On day three of a hike, that extra half pound feels like a brick in your pack.
• Software correction is scary on paper but in practice, the loss of resolution at the edges is barely measurable unless you are printing massive posters.
• Weather sealing is the real mvp. I got caught in a downpour and the one i ended up with didnt skip a beat. Tbh if you are mostly at f/8 on a tripod, the extra stop of light on the Canon RF 15-35mm f2.8L IS USM is basically just dead weight. My experience was that the lighter Canon RF 14-35mm f4L IS USM profile meant the camera stayed in my hand instead of the bag, which is the most important spec anyway... just something to consider.

honestly i wouldnt sweat the distortion or vignetting on that f4 lens... the r6 handles those corrections so well in-camera that you really wont notice it in your final shots. if youre mostly shooting landscapes on a tripod like you mentioned, the f2.8 is probably overkill for what you need. glacier has some of the best dark skies in the country though so i gotta ask... are you planning on doing any astrophotography while youre out there? also how much hiking are you actually planning to do? carrying that heavier glass up a mountain trail gets pretty old after a few miles so the weight difference is definitely something to think about. if youre just doing standard landscapes i think the f4 is the smarter play for your back and your wallet.

look, i've been shooting landscapes for a couple decades now and honestly, you're overthinking the f/4 vs f/2.8 thing for mountains. if you're on a tripod at glacier, you'll be stopped down to f/8 or f/11 most of the time to get that deep focus anyway. the Canon RF 14-35mm f/4L IS USM is practically made for this. i've used it extensively on my R6 and while people complain about the raw distortion, the software correction is basically seamless nowadays. you wont notice a difference in a large print. spending that extra grand on the Canon RF 15-35mm f/2.8L IS USM just to have f/2.8 for landscapes doesn't make sense financially imo. if you're really worried about missing out on milky way shots, just grab a Canon RF 16mm f/2.8 STM as a secondary lens. it weighs nothing and fits your budget perfectly alongside the f/4 zoom. focus on the light and the composition, the f/4 glass is plenty sharp for an R6.