How many exporures for HDR?

Amount of radiation needed obviously depends on the scene, but before that in many cases insufficient 3 exposure in increments of 1.66 or 2 EV Minor strokes do not recommend, it makes no sense to play in an EV. In theory, would make a measurement point in the brightest and darkest parts of the scene, the quantity needed to calculate radiation, etc. In practice, the usual (using, D-SLR) doing an irradiation, roughly in line with the measurement matrix, and then check the histogram if it points to the clear shift towards overexposure / underexposure change parameters and perform another trial. If it is correct as far as erasing pictures, run bracketing, attach the hose and doing a series. If possible, you may want to change the way the camera's way of making a series of bracketingowych so as to begin from underexposure, and the middle performed exposures, and ended with an X-ray (-, 0, +). The Canon's default is different (0;-;+) and then hinders orientation. The pictures of a strong light source in the scene usually requires more of the radiation, I am often in such cases, the fifth.