This book is the experience summary of author’s 50 years work on imaging technology in the exposure parameters selection of Radiography, described the author’s understanding of traditional Radiography exposure parameters, and put forward some new ideas, such as: image grayscale levels is a important standards of image quality; grayscale levels and contrast both are photo’s keys indicators and are restraint each other; the best balance between them is the ultimate goal of the parameters selection beyond the appropriate level in density; exposure parameters harmonious changing is the right means to achieve the above objectives; Limitations and proper use of the AEC; the selection of exposure parameters of digital Radiography; and so on.