First off, both are dedicated luminescence microplate readers that have been certified DLReady from Promega. These luminometers are upgradeable to multi-mode microplate readers with additional detection modes including fluorescence intensity, time-resolved fluorescence, fluorescence polarization and absorbance. Although both readers can be upgraded to include absorbance, the LUMIstar Omega can be upgraded with a UV/Vis absorbance spectrometer and the LUMIstar OPTIMA has optional filter based absorbance. The LUMIstar Omega is also capable of reading AlphaScreen/AlphaLISA after an upgrade and the LUMIstar OPTIMA cannot. The LUMIstar Omega is also more sensitive (20 amol/well ATP) than the LUMIstar OPTIMA (30 amol/well ATP).
For more information on all microplate readers from BMG LABTECH capable of reading luminescence, see http://www.bmglabtech.com/products/microplate-reader/luminescence.cfm
AlphaScreen and AlphaLisa are registered trademarks of PerkinElmer, Inc.