Commissioning of the ATLAS Electron and Photon Trigger Selection

First collisions at a center of mass energy of 7 TeV at the Large Hadron Collider (LHC) were recorded by the ATLAS at the beginning of 2010. Data selected by the hardware based Level-1 (L1) trigger was processed online by the software based High Level Trigger (HLT) running without active rejection. This paper gives an overview of the calorimeter based performance of the electron and photon triggers during the initial 2010 running period; these trigger will play a key role in the physics analysis in ATLAS. Examples of comparisons of the three trigger levels with the offline reconstruction will be presented, such at the L1 efficiency and the distributions of the calorimeter based selection variables used to distinguish between signal and background. This is an important step in the commissioning of the trigger system to ensure its correct functioning. Results from this first data are very encouraging. At the end a brief outlook on the commissioning steps and on the evolution of the e/$gamma$ trigger strategy with increasing luminosities will also be given.