  Electro-Multiplying CCDs offer a unique combination of speed, sub-electron
noise and quantum efficiency. These features make them extremely attractive for
astronomical adaptive optics. The SOUL project selected the Ocam2k from FLI as
camera upgrade for the pyramid wavefront sensor of the LBT SCAO systems. Here
we present results from the laboratory characterization of the 3 of the custom
Ocam2k cameras for the SOUL project. The cameras showed very good noise
($0.4e^-$ and $0.4-0.7e^-$ for binned modes) and dark current values
($1.5e^-$). We measured the camera gain and identified the dependency on power
cycle and frame rate. Finally, we estimated the impact of these gain variation
in the SOUL adaptive optics system. The impact on the SOUL performance resulted
to be negligible.
