It is hard to imagine a tougher venue for a photography show than Munich’s Haus der Kunst, with its vast, uninflected spaces and general pathlessness, but the recent survey exhibition by the Berlin photographer Michael Schmidt met the challenge triumphantly. Curated by Thomas Weski and titled “Grau als Farbe” (Gray as Color), it comprised nearly four hundred black-and-white photographs grouped, for the most part, to reflect the previous coming together of many (though by no means all) of them in the brilliant and original photo books Berlin Wedding (1978), Waffenruhe (Ceasefire, 1987), Ein-heit