The other day I saw The Oxford Murders (excellent movie, by the way), which is based on a book of the same name (in English) by Guillermo Martínez. The original book was in Spanish, titled "Crímenes Imperceptibles", which literally means "Imperceptible Crimes". Now, how do you think they translated title of the movie back to Spanish? Do you think they used the original title, which would guarantee the translation conveyed what the author meant in the first place? If you answered yes to the last question, then A) you are wrong and B) I suck at implying my opinion through rhetorical questions. They translated it back as "Los Crímenes de Oxford", which literally means "The Oxford Crimes". Why? Why wasn't the original title good enough?
At the root of the problem is the fact that the first translation of the title wasn't literal. I can understand non-literal translations when the title relies on wordplay, or a common phrase on the original language that has no equivalent. In those cases, they are necessary. But in this case, there was no reason to replace "Imperceptible" with "Oxford" (ignoring changing crimes for murders, which is pretty much irrelevant and was probably a cultural thing). The author decided to emphasise the fact that the murders were imperceptible, rather than that they took place in Oxford. Why? I don't know. He had his reasons, or maybe not. Maybe he did it at random. But it doesn't matter, because the point is he did. The job of a translator is to try and convey the author's original ideas as clearly as possible, and I don't see how changing the title helps.
As a consequence of this, whoever translated the movie, which was originally in English, to Spanish, has a problem.* Is it best to translate the title of the movie literally, or is it better to follow the original title? That depends on your view of the relationship between the movie and the book. If you consider the movie to be an adaptation of the book to another medium, then it is clearly best to make the translation as close to possible to the true original, which is in this case the book. If, however, you consider that the movie is a separate and independent work that is simply based on the book and it deviates enough to merit a title change, then translate the title accordingly.
I haven't read the book yet, so I can't make a definite judgment in this respect and I'm left with few sources for speculation. What can I consider? Well, for example, that the director is Alex de la Iglesia, who is Spanish and presumably read the book in its original language. Did he give the movie that title because he thought it better described the changes he made, or just so that it would be easier to identify movie with book? I don't know, but the latter is considerably more likely.
Until I hear something definite from either Guillermo Martínez or Alex de la Iglesia regarding the titles they chose (and that's not likely to happen) or I read the book, I'm left to conclude that it would have been better to translate the title according to the original title of the book. Feel free to call me an idiot and explain why translators choose to change titles for no apparent reason. I always wanted to know that.
*Note: I'm not saying that the translator actually thought about this, but I would if I where in his place. Maybe that's why I limit myself to translating my own blog posts, in which I know with 100% certainty what the author meant in every case.