  This study presents a method for determining the mass, angular momentum, and
charge of Kerr-Newman black holes by analyzing the red/blue shifts of photons
emitted by geodesic neutral massive objects. We derive the equations of motion
for photons in the Kerr-Newman spacetime. We obtain explicit expressions for
redshift/blueshift photons emitted by an object orbiting a Kerr-Newman black
hole. Finally, using the Boyer-Lindquist coordinates, we express the red/blue
shifts in terms of the metric parameters.
