Catalyzes the reversible reduction of NADP(+) by F420H(2). In this reaction the proS hydrogen at C5 of F420 is transferred into the proS position at C4 of NADPH. NADP(+) + reduced coenzyme F420-(gamma-L-Glu)(n) = 2 H(+) + NADPH + oxidized coenzyme F420-(gamma-L-Glu)(n) Optimum pH is 8.0 for NADP reduction with F420H(2). Optimum pH is 5.5 for F420 reduction with NADPH. Optimum temperature is 80 degrees Celsius. Is highly thermostable. Homodimer. Belongs to the F420-dependent NADP reductase family.