Charged Dilatonic Black Holes: String frame vs Einstein frame
  The descriptions of Reissner-Nordstroem and Kerr-Newman dilatonic black holes in the Einstein frame are compared to those in the string frame. We describe various physical measurements in the two frames and show which experiments can distinguish between the two frames. In particular we discuss the gyromagnetic ratios of black holes, the decay law via Hawking radiation and the propagation of light on black hole backgrounds. 
R. Casadio and B. Harms