Addition:
When using the MySQL client library, then you should prevent a conversion back to your connection's default charset. (see mysql_set_character_set()[1])
In this case, use an additional cast to binary:
SELECT column1, CAST(CONVERT(column2 USING utf8) AS binary)
FROM my_table
WHERE my_condition;
Otherwise, the SELECT statement converts to utf-8, but your client library converts it back to a (potentially different) default connection charset.