In their natural habitat, Japanese maples are primarily understory trees that grow in dappled forest sunlight along the edges of woodlands. Same goes here in the United States. That being said, there are a few Japanese maple varieties which have demonstrated a higher tolerance to sun, even in the Deep South. I live and garden in mid Georgia and have over 30 varieties of Japanese maple growing in my landscape. Some are growing in shady sites, some full to mostly sun. Below is a list of varieties I've found that really stand up good to direct sun or mostly sun.
This is the original Japanese maple. It is grown from seed and it provides the rootstock for all grafted varieties. The tree has green leaves. 20 feet or more in height and spread. more details and photos
A graceful, vigorous growing upright tree that tolerates full sun. Leaves start out rosy-red in spring, deepening in color to plum red, then to a bronze-orange towards the end of summer, and finally a crimson-purple in fall. 20 feet or more in height and spread. more details and photos
The most popular of weeping, red lace leaf varieties. Deep red leaf color holds well through summer turning bright crimson-red in fall. Mounding growth habit. 5 feet or more in height and spread (taller if high-graft). more details and photos
Very similar to "Bloodgood," Emperor I has has a faster growth rate and leafs out about two weeks later in the spring, an advantage in areas prone to late spring frosts. Deep red leaves lasts throughout the season, turning fiery crimson in fall. 20 feet or more in height and spread. more details and photos
A red leafed lace leaf that holds its color well, turning brick-red in fall. More upright than other weeping forms with long, arching red arms. 6 feet or more in height and spread but can be kept lower with pruning. more details and photos
I've tested Hefner's Red over the past few years in our trial gardens here in mid-Georgia and it has lived up to it's reputation for superior sun tolerance. It holds its red color better than any other red leaf variety I've grown. 20 feet in height with a similar spread so give it plenty of room to grow. more details and photos
A very fast grower with cascading branches. One of if not the darkest red of the lace leaf Japanese maples, holding color well through the season and turning brilliant crimson color in fall. 6 feet or more in height and spread but can be kept lower with pruning. more details and photos