Saw this earlier but just now responding... Building on the earlier suggestion about the 14mm distortion, I actually went with the Canon RF 15-35mm f2.8L IS USM for my own kit and I've been really happy with how it performs. I'm usually pretty cautious about gear that relies too much on software to fix optics, so the 2.8 felt like a safer bet for big prints. It works well and I've had no complaints even in some rough weather. A few quick thoughts on why it works:

• Sharpness in the corners is way more natural.
• f/2.8 is nice for astro if you get clear skies in Glacier.
• It feels very solid on the R5 body, well balanced. If you're worried about weight, you could check out the Canon RF 15-30mm f4.5-6.3 IS STM as a light backup, but honestly, for that R5 II sensor, you want the best glass possible.

Building on the earlier suggestion, the 15-35mm is definitely the more honest lens from an optical standpoint. If youre dropping several grand on a body like the R5 Mark II, it kinda feels wrong to rely on software to stretch out your corners. The Canon RF 15-35mm f2.8L IS USM is basically the gold standard here, tho its a heavy beast to lug around Glacier for a week. If you do go with the Canon RF 14-35mm f4L IS USM to save cash, just remember to stop down to f8 for the best sharpness across the frame. Also, since you're saving money on the glass, definitely grab a high-quality filter like the Breakthrough Photography 82mm X4 CPL. On that high-res sensor, a cheap filter will ruin your sharpness faster than a bad lens will. Its a balance of weight versus perfection... usually the f2.8 is the safer bet for gallery work.

I've been thinking about your question and I'm gonna have to respectfully disagree with the 2.8-only crowd. The Canon RF 15-35mm f2.8L IS USM is an amazing piece of glass, but for a trip like Glacier, the weight is a massive trade-off. If you are hiking up to Grinnell Glacier or doing anything long distance, every ounce counts... it is just physics. The Canon RF 14-35mm f4L IS USM is plenty sharp for big prints once you stop down to f/8, which you will be doing almost every time for landscape anyway. Honestly, the digital correction is a non-issue in modern workflows and it produces beautiful files. It is a very reliable lens that wont break your back or your budget as much. Since you mentioned printing big, maybe look into a really stable tripod setup instead of the heavier lens? Something like the Peak Design Carbon Fiber Travel Tripod is a solid choice for the R5 II. It is super light but holds that body steady for those long exposures during blue hour. I would also grab a Hoya 77mm Variable ND Filter to help with all the waterfalls you are definitely gonna see there. Much easier to carry than a whole stack of glass.

Since youre printing big, I would suggest being careful with the 14-35mm at its widest setting. On the Canon RF 14-35mm f4L IS USM, the native image doesnt actually cover the whole sensor at 14mm, so the camera uses heavy digital correction to stretch those corners out. On a high-res 45MP body like your R5 II, you might notice some softening in the extreme edges when you blow things up... its basically the price for that extra 1mm of width. A few technical bits to watch out for:

• Heavy digital distortion corrections can definitely eat into your raw resolution.
• The Canon RF 15-35mm f2.8L IS USM has a more traditional optical design that stays sharper across the frame.
• Make sure to check if you really need f/2.8 for your specific style. Personally, Id grab the 15-35mm for the cleanest data if youre doing gallery-sized prints. Let me know if you want to chat about filter setups for Glacier!

Bump - same question here

@Reply #4 - good point! Weight is definitely a killer on those long hikes, but I'd still be careful with the 14-35 for high-res prints. If youre really worried about sharpness across the whole frame, the Canon RF 15-35mm f2.8L IS USM is the safer investment for that R5 II sensor. Compared to the old EF lenses or third-party options, staying native with the high-end L series is the only way to ensure the weather sealing actually holds up out there. The digital stretching on the f4 might look fine on a screen, but it can get a bit sketchy when you blow it up to 30 or 40 inches... you dont want to see any smearing in the rocks. I would suggest making sure you have a solid backup too. If you can handle the extra bulk, the Canon RF 24-105mm f4L IS USM is basically a tank and will give you way more reach for those distant peaks across the valley. Ngl, those Glacier winds can be nasty, so having something robust is key. Just make sure to keep some Zeiss Lens Wipes handy for the mist... you dont want to ruin a shot with a smudge.