Michael, I like the image under the overpasses. At first glance, I thought the light between the highways were fluorescents until I looked closer.
On the product shots, the concept is there, but your execution needs to be better. Some tips: Dust sucks on table tops. (1) I always get my lighting down first and then dust and clean everything before the final capture. (2) If you are shooting with a black background, you should be using a 4 1/2 foot black sweep, at least, and have it far enough back so it is almost not fulling the frame. If you have the room, use a 9 foot sweep. This will allow as little light hitting the background as possible, rendering it completely black in camera. Also, the black plexi is reflecting the background, so if the background is completely black the plexi will be too. (3) The exception to this will be the horizon line, but if the plexi is big enough, the horizon will disappear from being out of focus. (Same is true with on white images.) (4) Flag your lights to keep even less light hitting the background. (5) Surround your set with black cards, which will kill any reflections. (6) If you are thinking about really getting into this, buy a 4 or 5 foot wide roll of full diffusion gel and shoot your soft boxes through the gel. This way you avoid the harsh reflections of the soft box edges and you can control how soft or hard the edge reflections will be. The further the softball is from the diffusion, the softer the edge will be on the product.
All of my on black images are very close to how I want them to be through camera. Adjustments to tonalities, clarity and color are made, I may clip the bottom of the histogram to value 4 or 5, and compositing is certainly part of it, especially for splashes. However, the lighting out of camera is almost identical to how it looks in the final shot.
