The trademarks of a traditional landscape image are wide angle lenses and extreme sharp focus, which is why many DSLR’s landscape mode is designed for short focal lengths and increased depth-of-field. It’s the exact opposite of portrait mode that’s been designed for longer focal lengths and limited depth of field.
For most camera’s the built-in flash and AF-assist light cannot be used in this mode, because most land-scape subjects are located near infinity and the flash’s range is limited. Powerful speed-lights sometime function in landscape mode but you could only rarely take advantage of this function, since the mode is not designed for use with flash.
As in all subject programs, selective metering and manual exposure correction can’t be activated which may cause problems with strong back light and the kind of high subject contrasts found in wide-angle photography.
To make maximum use of the landscape mode, you should use lenses that have wide angles of view or zoom lenses with wide-angle settings. You can use landscape mode with 35mm focal length lenses but lenses with focal lengths shorter than 20mm inherently offer large depths-of-field even at maximum aperture, which can be further increased by stopping down to smaller apertures (if your camera lets you) making it possible to capture both foreground and background in focus.
The wide-angle characteristics of lenses decrease with increasing focal length but detail shots made with telephoto lenses are also part of landscape photography. Unfortunately, many camera’s landscape modes don’t allow this option. With the small aperture required for large depth-of-field, shutter speeds become slower, increasing the risk of camera movement, unless of course it’s an image stabilized lens or body which gives you more elbow room for slower shutter speeds. If this is not the case, the shutter speed sometimes flashes in the viewfinder as a camera shake warning.
Tip: Landscape mode is designed for overview shots using wide-angle lenses. Focus lock while touching the shutter release or manual focus allows you to include parts of the foreground in your composition. A combination of wide-angle lenses and landscape mode emphasizes depth-of-field allowing you to make great shots with a interesting foregrounds and vanishing backgrounds.