For macro, I assume you're using a tripod as well? Try using F8 or F11 and above. Use 2 sec timer if shutter speed too slow (ah all shutter speed 0.5 secs huh?). See if the whole subject in focus looks nicer or part of it blurred.Oh yeah, since it's set-up, you have all the time in your hands to have a perfect exposure. So might want to minimise noise by using lower ISO like ISO100. It helps to bring out the details of the objects.
haha..ok..thx! will try it again..