Complex sentence: The high sensitivity of this photocathode, greater than 900 µA/lm allows more effective low light response, however this is offset somewhat by the thin film which typically blocks up to 50% of electrons.
Split into simpler sentences: The high sensitivity of this photocathode, greater than 900 µA/lm, allows more effective low light response. This is offset by the thin film, which typically blocks up to 50% of electrons.