Saw the film Public Enemy tonight and it's good. A well-told story -- and a feast for any retrotechnologist, generally lacking in serious anachronism.
That said, three did stand out: Microphones used in a Senate hearing in set 1933 or early '34 were nifty Western Electric 639A or B types, introduced in 1938 (and later made by Altec, fine mics and one of the currently more readily-available of the old microphones, which is sort of important if you're doing film props). More jarringly, a "typewritten" page is shown on-screen, taking up about a third of the screen image. Alas, it is a kerned, book font, not a typewriter font. That one should have been an easy catch and fix but it was missed. Last, a meter on a piece of equipment that shows up in several scenes had obviously been backlit with a distinctive blue LED. Oops!
On the other hand, you'd have to be some kind of, I don't know, tech geek to catch two of the three; for a period piece, not so bad. Guns looked correct to my eye (better ask Tam), clothing and hairstyles were better than usual, likewise interiors. The filmmaker put in a lot of work to make the last bit of Dillinger's life real and it paid off.
Johnny Depp was a fine John Dillinger, vanishing into the character as he does so well. My advice: go see it. If that's the kind of thing you like, you'll like it a lot. I did!
2 weeks ago