摄影距离
2.Method: Taking the focus-film distance as a single varian, the 24 chest radiographs in various focus-film distance were selected according to AEC standard and we confirmed 7 evaluation points were selected and the density of each evaluation point were measured by densitometer.
3.Parallax correction mark in the viewfinder can help avoid chopp head and feet off at close distance.
4.Abstract: It is very necessary to measure the Guide Number (GN) accurately in special photograph.based on the mode of the incidence.The measuring method and the structure are designed.The GN of flash lamp is attained.The best aperture in different distance can be gained.It for its excellent character and lower cost that we use the micro-controller of AT89C2051.
