Another reviewer--perhaps on another website--criticized the photography for being grainy. S/he is perhaps referring to the first twenty minutes or so when the action is being performed behind a scrim. The photography is so sharp on the Blu-ray, in fact, that you can see the individual strands within the warp and weft of the scrim. The balance of the show is crystal clear.
This is a wonderful memento of a performance that I attended in 2009. The singing, acting, playing, scenery and costumes are actually better than I remembered. In case anyone wonders, this opera was presented concurrently with a production of Wagner's Die Walküre, which was presented on a giant turntable tilted steeply toward the audience that was too bulky to be removed for Die Vögel. The scenery for Die Vögel was adapted to that turntable.