* First produce the JSON file for the run range of interest

      filterJSON.py --min 190456 --max 193621 Cert_190456-208686_8TeV_22Jan2013ReReco_Collisions12_JSON.txt --output JSONoutput.txt

  * And then calculate luminosity for the selected run range

      pixelLumiCalc.py recorded -i JSONoutput.txt --hltpath "HLT_Mu40_eta2p1_*"  

  * The latest CMS lumi uncertainty is 2.5% based on pixel counting as reported [[http://cds.cern.ch/record/1598864|here]]