We demonstrate the ability of high-speed acquisition (up to 30 kHz) of dynamic speckle to provide images of the human vascularization at various scales. A comparative study involving the speckle contrast, the first term of the intensity autocorrelation function, and the zero-crossings of the field intensity is proposed, together with a proper preprocessing scheme based on image registration and filtering. Experimental results show the potential of the first term of the autocorrelation function to provide efficient model-free mapping of the microvascular activity (i.e. small-scale random motion associated with the presence of a vessel). With the help of this parameter, various scales of vascularization including large vessels in the wrist, microvessels in the ear and fingers, and thinner inflammatory structures are observed, which suggests the imaging abilities of this parameter are broad. The minimum acquisition time is shown to be of the order of 50 ms, demonstrating video imaging capabilities.