I tried this diffuser with Canon SX20IS indoor shots for portraits. Certainly it "diffuse" but the flash light is very visible on the portraits, I would say that it derives that 1/3, but its main flaw in my opinion is the discoloration that "yellowed" with the diffuser. After a few tries I get more beautiful pictures without diffuser but playing only with the Speedlite 430 EX orientation II (which is a marvel)