http://www.npl.co.uk/upload/pdf/20121128_irmf_minutes.pdf - 44.10 200W security light @ 2cm 500W security light @ 12cm Approx equivalent to high sun these tests are now included on page 29 of gpg 14 issue 2 http://www.newport.com/Introduction-to-Solar-Radiation/411919/1033/content.aspx With earth sun distance at 1AU (astronomical unit) 149,597,890 km we have 1120W/m2 hitting the ground due to scattering and the atmosphere that's radiant flux. A class G star like our sun has Luminous efficacy (lm/W) of 93 so that's 104160 lumens per square metre (lux) (the solar illuminance constant Esc is 128 000 lux) so we're not far wrong. the spectral output of the sun is a close match to a 5800K black body http://upload.wikimedia.org/wikipedia/commons/4/4c/Solar_Spectrum.png based on http://rredc.nrel.gov/solar/spectra/am1.5/ http://rredc.nrel.gov/solar/spectra/am1.5/ASTMG173/ASTMG173.xls What's more important, the lux or the spectral match... Well according to philips your 200 and 500w tungsten halogen have lm/w of 17.6 and 19.8 200*17.6 = 3520 lumens 500*19.8 = 9900 lumens however a security light reflects and focusses light... this confuses matters Typical cheapy LED floodlight claims 20W model - 6000-6500K 1600-2000 lm 30W model 2400-3000 lm cie2.nist.gov/TC1-69/Leeds/Calculating%20CRI-CAM02UCS-v2.xls http://www.hamamatsu.com/resources/pdf/etd/PMT_handbook_v3aE-Chapter4.pdf http://www.hamamatsu.com/resources/pdf/etd/PMT_handbook_v3aE.pdf www.jedec.org/sites/default/files/docs/JESD51-50.pdf https://www.google.co.uk/url?sa=t&rct=j&q=halogen%20lamp%20spectrum%20download&source=web&cd=11&ved=0CDkQFjAK&url=http%3A%2F%2Fwww.newport.com%2Ffile_store%2FSupporting_Documents%2FTech_Ref_Spectral_Irradiance37.pdf&ei=ldwyVMuwEdDiapmXguAH&usg=AFQjCNGU-STBtN9LIIpO6CKOXFlFR26tjw http://www.newport.com/Information-on-Oriel-Spectral-Irradiance-Data/383232/1033/content.aspx http://www.newport.com/Technical-Note-QTH-Lamp-Spectral-Irradiance-Data/409204/1033/content.aspx Spectral Irradiance Calibrations www.nist.gov/calibrations/upload/sp250-20.pdf DF]Spectral irradiance model for tungsten halogen lamps in 340–850 ... lib.tkk.fi/Diss/2010/isbn9789526031569/article1.pdf