Another non-scientific test in my garage. A Strand-Century 2212, with a 500W EHD lamp, dirty lenses and all, at 14'-0": No color=75.4 F.C.; with Apollo GelShield™=61.5 F.C.; thus a transmission value of 81.6%. I don't have any other brands to which to compare this. If anyone has any Rosco Thermashield or Super Heat Shield™, or Lee Filters #269, or GAM HeatShield99, it would be interesting to post your results.