Manual Exposure Mode
A correct exposure of a landscape shot is very important. Even though modern digital cameras features advanced algorithms to calculate the right exposure, they still may fail some difficult conditions. Manual exposure mode in these conditions helps a lot in order to achieve correct exposure.
No Manual Focus Mode
Manual focus in landscape photography is very useful in order to have a sharp image and minimize the areas that are out of focus. Autofocus may not consistently give you the best results. 38 mm - Poor Wide Angle Coverage
Even though there are very good examples of landscapes photos taken with tele lenses, most of the landscape photos are taken with wide angle lenses. Unfortunately, with the widest focal length of 38mm, Sony H20 doesn't provide a real wide angle coverage. No RAW shooting capability
RAW files contains much more color information compared to JPEGs, and gives you more room for post processing without significant quality loss. They provide wider dynamic range and option to recover shadow and highlight clipping to some degree. Small 1/2.3" (6.17 x 4.55 mm) sensor
Sony H20's small sensor struggles in low light situations compared to larger sensors. Very Low Resolution Sensor: 10.0MP
Landscapes photography is where you need the maximum resolution. Unfortunately Sony H20's 10.0MP sensor doesn't deliver much and limit you with smaller prints and less fine details. No Environmental Sealings
Landscape photographs are taken outdoors and you should be prepared for all kind of weather conditions.