Honestly, I've spent years lugging heavy glass around, but for Iceland, weight is your worst enemy. If you really want that ultrawide perspective without the bulk, look at the Panasonic Lumix S 20-60mm F3.5-5.6. It is surprisingly sharp for landscapes. If you need something wider, the Sigma 14-24mm F2.8 DG DN Art is a beast, though it is heavy. Dont worry about f/2.8 for landscapes, just bring a solid tripod.

Honestly, skip the expensive glass if you are heading to Iceland. I have been shooting landscapes for years and in my experience, the Panasonic Lumix S 14-28mm F4-5.6 Macro is the smarter buy. You lose the f/2.8 aperture but for landscapes, you are gonna be stopped down to f/8 or f/11 anyway. The 14mm focal length is massive for those wide vistas and honestly, having those extra 2mm makes a huge difference when you are standing in front of a waterfall. Save your cash for the trip itself. The Sigma 16-28mm F2.8 DG DN Contemporary is sharp, sure, but the Lumix is usually cheaper and weighs way less. Carrying heavy gear all day in the Icelandic wind is a nightmare. Go for the 14mm and use the extra money for a nice filter set instead.

Commenting to find later

Stumbled upon this thread a day late, but I gotta be honest, I've had some really frustrating experiences with those zooms in extreme weather. Unfortunately, the build quality on a few of those lighter wide-angle options hasn't held up as well as I expected when things get wet and windy. Iceland is brutal, and gear failure is a nightmare I wouldnt wish on anyone. Before you drop a bunch of money, I have a couple of questions to help you figure out what's actually gonna survive the trip:

• Are you planning on using physical screw-on filters for long exposures, or are you gonna need a full adapter setup?
• Whats your actual budget for the lens, including potential repairs or weatherproofing gear? If you go with something cheaper, just be super careful with the seals. Hope you get some killer shots out there regardless!