From what I understand, it's zero. But Adsense needs words to figure out what kinds of ads to serve. BUT... they can also get these from your domain name, the name of the directory(ies) the page sits in, the name of the page itself, and the metatags within the page. Assuming you're talking about a page of image(s), the names of the images will be taken into account also. Of course, you understand the page has to have SOME content. Still it's certainly better to have more words on the page - and of course gives the search engines something to grab onto.
Google's terms say that you must have some content on the page where you want to display ad. And its obvious if you have content then only google will be able to decide what types of ads to put there. Without content the ads will not display. So you must have at least 2 lines of content. But if you put only 2 lines in content then it becomes MFA.And its the one way to be banned. So its best to put enough content on page and then put adsense on it. Its good for both you and adsense.
I don't think that Google is banning MFA sites, because they are getting high paying keywords and most of hem are paying for adwords.