(An exception is when you are a government delegate voting for chancellor, in which case you pay a fine of 1000€, especially after the president has clarified this rule to new delegates repeatedly)
The election council and a lot of privacy-conscious citizens weren't amused to say the least, but a subsequent ruling by a judge turned out that it isn't strictly speaking illegal, because the law doesn't explicitly prohibit photography in the ballot booth. So until parliament enacts a law that forbids it (like Germany), we are stuck with this rather dubious phenomenon.
At least we've banned voting computers for a good while — the ones we had ran closed source software and the votes cast couldn't be verified by the voters or the election council — so there's that.
This requires the poll workers to be somewhat impartial. If they are not all bets are off. In the German Democratic Republic voters where socially pressured (by official policy) to not use the booths at all.