If not for its PG-13 rating, “Jack the Giant Slayer” would be an old-fashioned, family-oriented fantasy adventure, the type that local television stations used to run on Sunday afternoons.

Just a few edits would have guaranteed a PG, but that rating is considered uncool these days. Parents wondering if this is appropriate viewing for their children should take the PG-13 under advisement. The main reason for the rating is a particularly grotesque, almost comical, death of a giant near the end of the film, and like almost all of the film’s violence, it is rendered in CGI.

The rating aside, Bryan Singer confidently captures the earnest spirit of such! mildly scary family features as “Jason and the Argonauts” and “The Seventh Voyage of Sinbad.” Those classics had Ray Harryhausen’s stop-motion creatures and “Jack” has CGI giants. The giants aren’t especially realistic, but neither were the skeletons in “Jason,” and 50-plus years on, that fight at the end remains a thrilling special effects sequence.