DC: When James/Lily/Sirius/Dumbledore died, why couldn't Harry just talk to their portraits?

Seriously! Remember in Order of the Phoenix when Dumbledore used to talk to the portraits of previous headmasters of Hogwarts, like Phineas Nigellus and he kept ordering them around? So why couldn't Harry just grab a portrait of the dead and talk to them? I have been racking my brains for so long!