There are a number of technical requirements that must be obeyed and then, there are specific difficulties that come with subtitlia, the language of subtitling.
A few basic principles to subtitling or screen translation:
Translate everything
Translate even on-screen text, such as names of institutions, road signs, billboards that stay on-screen and are significant to the plot. Also, names, titles, ranks or positions of speakers, etc.
Do not translate literally
The art of the subtitler is to understand the plot and what is being said in the original content and translate it as faithfully and accurately as possible. Do not be faithful to the letter of the text, but to the sense of the content. This is not nearly as easy as it sounds, in subtitles you only have a limited number of characters per subtitles (usually 36-40 characters), hence the subtitler must have a good knowledge in the art of summarizing.
Summarize
The subtitler should give the most concise and accurate translation and interpretation (adaptation) of the original text into the target language in the fewest number of words possible. The subtitler should know and decide what to render to the public in order to carry out and insure understanding of the plot and of the main points. In translation from English into a Latin language (such as Romanian) you will have on your hands a short English text that translates into a many long words, so you’ll have to decide what to retain and what is in fact superfluous. It is ok to leave out some content as long as it will not prove particularly important or relevant to the plot later on.
Puns, play on words, proverbs – adapt, replace, recreate
It is always difficult to translate jokes that are hilarious in English, but mean nothing into your language. The same with puns or proverbs. In this case, be creative, find something similar into your language that will render the original sense and contribute to understanding the message and the plot. If you are lucky to have a similar saying in your language, good for you. If not, adapt it or replace it completely.
Language used, from specialized to slang
If you are translating ER, make sure you use good specialized dictionaries and research your every word. If you are translating slang, make sure you use words that are in the dictionaries. Also, you should decide what is the corresponding level of slang into your language. The variety of levels you will encounter in subtitling is truly wide, you have to be prepared to handle any register of language, from academic, highly specialized to slang.
Consistency
There should be consistency throughout the entire translation, especially in such points as: numbers, measurements, names, nicknames (spelling, translation of names, etc), addresses, formal or informal level of address, acronyms, etc.
Punctuation
Every language has its own subtitlia. You will notice that by simply turning on the TV and reading some subtitles. The language rules (punctuation, especially) is not the classic one that you will find in every grammar book, but a specific one. Find out what the subtitlia rules are for your language and use it consistently.
Using italics
Some consider italics are not necessary, but usually subtitles use italics for: off-camera speech, text being read, the TV, the radio, songs, book or movie titles, and foreign words.
Measurements
Translation absolutely required from the imperial system into the metric system (unless of course you use the imperial system of measurements). The subtitler has to decide if there is need for precision to the very millimetre, or if the number in the original English text is just an approximation and should be rendered in the target language as an approximation.
Line division
Line division is particularly important to how subtitles look on screen and most particularly the speed of reading and comprehension. If the text fits on one line, keep it on one line, the viewer will be happy to see more of the screen. If the text does not fit on one line, then you should try to divide it as best as possible, keeping in mind the following basic principles:
1. Divide at punctuation marks (“,”, “.”, “:”, “…”)
2. BEFORE conjunctions (i.e. you should have the conjunction on the second line: and, or, because, etc.)
3. BEFORE prepositions (i.e. you should always move the preposition on the second line, ex: on, for, in, inside, on the outside of, etc.) Watch out for compound prepositions.
4. DO NOT SEPARATE a noun from its article (i.e. do not leave the article “a”, “an”, “the” on the first line and the noun on the second line).
5. NO DOT DIVIDE a name, whenever possible and whenever you have plenty of space the keep it together.
6. NO NOT DIVIDE compound or reflexive verbs (i.e. do not leave the auxiliary, reflexive, negative particle etc on the first line and main verb on the second line.)
7. NO NOT DIVIDE verbal phrases, idioms, expressions
8. Do not split abbreviations
9. Try not to divide the subject from the verb whenever the space allows it.
10. DO NOT LEAVE ONE WORD on a line even if it is followed by punctuation.
The basic principle to line division is to keep idea units and semantic units together; it will insure easier and faster reading and comprehension by the viewer.

The best of luck in translating for screen, a pleasant and rewarding job!

Cristiana Coblis