Early in my infancy, Richard Greene's Robin Hood was, for me, the real, the only portrait of Robin Hood. At that time, I could not notice the budgetary constraints, especially noticeable today in the minute sets where action took place. In the same way, this 1958 Invisible Man was, for me, the true depiction of the Invisible Man: a type of superhero, always fighting for justice. I was eight years of age at the time, so I was very surprised when I learned, later, that Wells original character was not a hero, but a very troubled man.
I enjoyed the I.M. effects very much and I never spotted a wire; however, quite often, things like telephones, pens and cigarettes behaved strangely when lifted by the invisible man: they tended to somehow oscillate, a movement not to be expected from an object supposedly held by a hand (invisible or otherwise).
Nevertheless, it was good and fun. ALL 26 EPISODES ARE AVAILABLE FOR WATCHING OR DOWNLOADING at Internet Archives dot org (Classic TV Section) or at Uncle Earl's Classic TV web site. Don't miss them.
I also agree with the previous commentator that ITC, very markedly at that time, usually offered products of a superior quality. I'm an admirer of Ralph Smart (the producer of this series), who would be later responsible for the excellent and unsurpassed Danger Man (Secret Agent Man) starring Patrick McGoohan.