An 85mm prime on full frame gives a short-telephoto view with slightly compressed perspective. That’s why it’s popular for portraits, but it can also be used for landscapes when you want a tighter composition, isolated details, or a more compressed look.

It’s not usually the first choice for general landscape work, because it isn’t wide enough for sweeping scenes and isn’t especially long for strong telephoto compression. Still, it can be useful for selected landscape subjects.

For focus range: focal length does not set one fixed “in-focus distance.” Most lenses focus from a specified minimum focus distance out to infinity. For example, the Nikon 85mm f/1.8G focuses as close as about 0.8 m / 2.6 ft.

How much of the scene is in focus depends on aperture, subject distance, and sensor size. At 85mm, depth of field can be quite shallow at wider apertures, but stopping down and focusing farther away increases it.

A simple way to preview 85mm is to use a zoom lens set to 85mm on your D800. That will show you the field of view and help you decide whether that framing suits the subjects you shoot.