May I suggest purchasing black velveteen (a little cheaper than velvet) but they work the same. The shadows caused by the flash seem to be dispersed by the hundres of points or threads of the velvet.
I usually take pictures with natural light coming in from one side., but the velvet background helps when the light is not strong enough and a flash is used. I personally do not like using a flash since it flattens out the tree..
On the other hand, here is a picture I took with a sky background 3 foot by 4 foot, which I painted specifically for taking picctures.
