The rule of thirds--that a time-tested compositional tool--says that in a scenic, you should place the horizon either a third or two-thirds up in the image. Well, sometimes, that's neither high nor low enough.
There are times when it makes more sense to place the horizon near the bottom edge of the frame. There are other times when the horizon should be right below the top edge.
Sky high: The high, far-away clouds at top right balance the nearby foliage at the bottom left of this shot. Sometimes, a low horizon creates a dramatic tension within the image. Photo by Mason Resnick
There is no hard-and-fast rule for determining where to place the horizon, but it has to do with making a photo with greater impact. If there's something interesting going on on the ground, raise the horizon. If a lot of think space is required, or clouds are particularly interesting and create a good interplay with what's on the horizon, place the horizon lower.
The low down: The sandy parking lot foreground adds an interesting detail that would have been lost if I'd followed the rule of thirds with a lower horizon. Camera for both images: Canon 30D with 18-55mm kit lens, zoomed out to 18mm. Photo by Mason Resnick
Study the scene, and try a variety of compositions changing the position of the horizon. and you may find that disobeying the rule of thirds is the best thing you could do for that photo.