Beard Man wrote in post #17454021
What is the best lens for landscape photography ?
There is no best. Landscape is a super broad genre. You can landscape with a 12mm, or a 600mm. It's just a difference in perspective and distance to target for intended field of view. You'll see a lot of "go wide angle" but that's not always the way to go. There's a ton of telephoto landscape that is stunning. You just have to consider what landscape you actually want to do, where, when, etc, and what you want out of it. You may find wide angle to be what you want, or just a normal field of view, or maybe you are going to want telephoto. Who knows. Use your 50mm to guide you, do you want wider than that, or have you ever tried using the 50mm in that way?
When I think of a "lanscape" lens, I think of three main properties as being important: (1) flare resistance, (2) corner sharpness when stopped down, (3) ability to take standard filters. The rest is secondary (things like max aperture, autofocus, IS, etc, are all not important to me on a landscape lens, because I tend to hyperfocal/manual focus, I'm on a tripod, and I'm stopping down for depth of field and sharpness, so I only focus on the above 3 properties in a landscape lens).
That said, it's hard to go wrong with a used EF 17-40 F4L lens, because it gives you great flare resistance, takes filters, and has good sharpness stopped down, and gives you ultrawide angle, wide angle and normal field of view (35mm~40mm) without overlapping with your 50mm. It's inexpensive for what it is.
Otherwise, I would look at good manual glass, primes, and options like that. A good 28mm prime can be a great lens to go with. Be it a modern EF 28mm F2.8 IS, or a 30 year old 28mm adapted manual focus lens like an old super takumar. Again, I still look at flare resistance, sharpness in corners stopped down, and ability to take filters as being important. If price is cheap on old manual glass, you can at least compromise since these lenses can be $10~30.
I do a lot of landcape at 22mm on APS-C, so on full frame, the equivalent would be a standard 35mm lens. But I use my 5D for portrait. I do landscape on APS-C typically.