It’s a constant droning, heavy and reverberant. Thick and all-consuming, it can be felt in your bones; your skin feels like it’s vibrating. Guilt, and the existential dread that can accompany it, can be agonizing, even when one isn’t conscious of what one is feeling, and Sabine Meier’s “Portrait of a Man” exhibition captures these emotions beautifully in a series of photos — as well as the descent into madness that precipitated the preceding events…