I'm translating a story that has appeared in English before. A few thoughts, in answer to rhetorical questions:
1) Why don't you just copy the other translation?
Because I am in this case translating the story directly from the original language, not via a third, as was the case last time. And the previous translator was not a native-speaker of either British or American English. If a story is translated via a third language, there will be inconsistencies. And the style, vocabulary and so on may be somewhat different. So copying it, then altering it, would be a tedious and long-winded process. Quite apart from any copyright problems that could arise; plagiarism is frowned upon.
2) Where does an existing translating help you?
An existing translation is definitely a help, as there are always things that remain obscure in any text. Every translator has blind spots. So someone else's translation is a useful back-up. If you only have the original text to go by you can also miss things, leave out a whole sentence, or similar. (That happened to me today.) Also, a translation into, say, French or German can be useful. Again, the French or German translator may have noticed or understood things you didn't. And sometimes the previous translator finds more felicitous expressions than you have thought of. The "why didn't I think of that?" factor is always present.
3) Will your translation be more widely available than the previous one?
I hope so. The previous translation was done by a Russian whose English was very good. While I freely admit that even at one remove he sometimes found clever expressions that I didn't, making me envious, the last time the story (dating from 1972) was translated into English it came out in a pretty obscure edition. It was published by Progress Publishers in Moscow in an anthology of stories called "The Love That Was" back in 1982. This anthology was printed, in English, in an edition of 3,700 copies worldwide. How many of these copies ever reached the West I do not know. I know the exact number of copies printed because one very useful thing printed in the back of every Soviet book was the publishing details, including the edition, the price [2 roubles 90 kopecks, in this case], the date the final manuscript was sent to the printers, and a few other details.
Author: Mati Unt
Story: "An Empty Beach"
Original language: Estonian
Previous translator into English via Russian: "Holly Smith" (the pseudonym of Sergei Roy, a Russian translator, editor and journalist)
Previous title: "The Naked Shore".
4) Why did you change the title?
Reading the story through, I thought that the word "beach" was more appropriate, as I've actually been to the island where the story is set. The word "naked" was probably added by the person translating the story into Russian, because the story is about a love triangle, jealousy and a little sex. But for me, the word "empty" conveys the original title better.
So, those are some practical, as opposed to theoretical, considerations that go through your mind when translating a text that has appeared in English before.