HOW TO SIZE AN OUTDOOR LANTERN
Selecting the right-sized outdoor lantern can sometimes pose a challenge. Follow these sizing guidelines for a fit that's just right.
The height of an outdoor lantern should be based on the height of the door:
DON'T UNDERSIZE YOUR LANTERNS:
As a rule of thumb, your lanterns should appear to be about half the size of your door from 50' away.
FOR 1 LANTERN:
If you place a lantern on only one side of the door, it should measure one-third the height of the door. The center of the bulb should rest 66" above the threshold of the door.
FOR 2 LANTERNS:
When two lanterns are used, they should each measure approximately one-fourth the height of the door. The center of the bulb should rest 66" above the threshold of the door.
TIP: In either case, if you choose a fixture with a long tail or top scroll, pay attention to the overall bulk of the fixture.
TIP: When in doubt, always go larger.
from http://www.hinkleylighting.com