What is the best landscape lens for Canon R5 Mark II?

Question

I finally pulled the trigger on the R5 Mark II after years with the 5D series and honestly I am kind of freaking out because my old EF lenses just arent hitting the same way on this new sensor. Ive been a landscape guy for over a decade so I know my way around a tripod and filters but this 45MP resolution is showing flaws in my EF 16-35mm f/2.8L III that I never noticed on my 5D Mark IV. Maybe its the adapter adding a bit of flex or maybe the sensor is just too demanding but the edge-to-edge sharpness is definitely taking a hit and I need this sorted before my trip to the Dolomites in like 19 days.

Im looking for the absolute best native RF mount wide angle because I cant risk coming back from Italy with soft corners. Ive looked at the RF 15-35mm but Ive heard some mixed things about the distortion at the wide end compared to the old EF glass and then there is the RF 14-35mm f/4 which is lighter but I worry about the diffraction when Im stopped down for those deep depth of field shots. I usually shoot at f/8 or f/11 but sometimes you gotta push it and I dont want the image turning into mush.

Here is what I am looking for:

Must handle the 45MP sensor without looking soft in the corners

Filter threads are a big deal since I use a 100mm square system and I really dont want to buy a whole new setup for a bulbous front element

Solid weather sealing is non-negotiable since Ill be in high-altitude conditions with possible snow/rain

Budget is around $2,500 but I could stretch it if there is a prime that absolutely blows the zooms out of the water

Weight matters a bit because Im hiking 10+ miles a day but quality comes first

Is the RF 15-35mm really the gold standard here or should I be looking at something like the 14-35mm and just letting the camera fix the distortion in-body? Or is there some secret prime Im overlooking? I am genuinely losing sleep over this because I dont want to spend two grand and realize I actually liked my adapted EF lens better... what are you R5II owners actually using for high-res landscape work?

CurtisPyday · Accepted Answer

I would suggest being careful about dropping nearly three grand right away. If youre shooting f/8 or f/11, you might not see enough difference to justify the cost of the fastest glass. Honestly, that 45MP sensor is brutal, but some of that softness might just be the adapter connection being slightly off. Before you blow the budget, consider these:Grab the Canon RF 14-35mm f/4L IS USM but look for a refurbished deal. It handles the 100mm filter system perfectly and saves a ton of cash.Skip the Canon RF 15-35mm f/2.8L IS USM unless you shoot astro. The f/4 is often sharper in the corners at landscape apertures anyway.Check your Canon Mount Adapter EF-EOS R for wiggle. Even a tiny bit of movement makes high-res files look like trash. Save that extra money for the trip itself. Italy isnt cheap.

PeterGow · Answer

Honestly, I went through this exact same panic when I swapped my 5D Mark IV for the R5. Spending weeks debating between the big f/2.8 and the f/4 version was stressful because I was terrified of losing that "L" quality on the 45MP sensor. Basically, I ended up grabbing the Canon RF 14-35mm f/4L IS USM for a scouting trip to the Sierras and it totally surprised me. Since you mentioned hiking 10+ miles a day, that weight difference is actually a huge deal. My back was way happier and the sharpness was... honestly better than my old EF 16-35. People worry about the distortion at 14mm, but the in-camera profiles handle it so well you wont even notice unless you are shooting architecture. For landscapes in the Dolomites, it is a non-issue. Edge sharpness at f/8 is stellar, way better than my old EF glass ever was. Plus, it uses 77mm filters so your 100mm square system will fit perfectly without needing new rings or dealing with vignetting from a massive front element. If you really need that extra stop of light for astro, the Canon RF 15-35mm f/2.8L IS USM is the heavy hitter, but it is a beast to carry. Quick tip: dont worry about diffraction too much until you hit f/13 or f/16 on this sensor. Stick to f/8 for the sweet spot and you will be golden. For the price and the weight, the f/4 is the practical choice for a high-altitude hiker.

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What is the best landscape lens for Canon R5 Mark II?