Robert_Charlton - 8:49 am on Jun 2, 2013 (gmt 0)
I think the reason is because on every page repeats the same text and just change some data (name of city dwellers, zip code, etc.).
Content is of poor quality but the same thing is repeated on every page.
Also I have the same site in another language so Google might consider it doubled.
How I can do to recover my visits?
hipotecamix - I think you've mostly answered your own questions by identifying the problems. Either you add unique and useful content, or you suffer the consequences.
I mention your questions right here because you also describe your site as being primarily just images. Several of the pages that JohnMu cited as being of low quality were simply pages of images with no relevant text... essentially just the page template. He also cited text pages with not much useful content on them. Conceivably, this kind of thing may run through a lot of the sites that were affected by this drop.
If you want to rank, every page really has to be good. To quote an important point that JohnMu made...
...make sure that all of your indexed pages are of the highest quality possible and that they are fantastic representatives of your website, in a way that all new users will be drawn in and want to recommend your website to their friends.
Google is going to continue to raise the bar, and either you pay attention to that, or you don't.