The V-STARS system measures special targets made of a thin 0.1mm thick (0.004″), flat, grayish colored retro-reflective material. This material has several advantages over conventional targets (typically a white circle on a black background). The retro-reflective material returns light very efficiently to the light source (they are similar in principle and operation to highway reflectors only much more efficient), and is typically 100 to 1000 times more efficient at returning light than a white target. A relatively low-powered strobe located at the camera lens is used to illuminate the targets, and makes exposure of the targets independent of the ambient light level. This means the object can be photographed in bright light or total darkness, and the target exposure will be the same.
Furthermore, the strobe power is low enough that the strobe does not normally significantly illuminate the object. Thus, the target and object exposure are largely independent with target exposure provided by the strobe, and object exposure provided by the ambient light. By setting the shutter exposure time appropriately you can expose the object to whatever level you desire. You can make a normal exposure, but usually you will want to underexpose the object significantly to make the target measurement easier and more reliable. Then, you can use the enhancement features available in V-STARS to enhance the object.