Landscapes

What makes a landscape photograph great?  I have been thinking about this a lot lately.  I have a real desire to master this area of photography and so it is natural to try to understand the difference between a competent landscape image and a truly stunning landscape photograph.  Obviously I want to be creating the latter.

The rules of design and photography remain the same for landscape photography as they do for any other branch of the art-form.  Balance, rhythm, proportion, dominance and unity are still the important principles.  The elements of color, contrast, value, texture, line and shape are still the tools we use to "design" the imagery.  So what makes a landscape image great?

Anyone?