Spare witness

Why did Diane Arbus view herself, if she viewed herself (viewfinder, focus, f-stop, etc.), as a spare witness, as despaired witness, as self-disposable? On a contact sheet: a frame, a self-portrait, a double-exposure. That look of anxiety in her subjects' faces. Faces must stain film and witnessing eye. Her eye is here for a while.

The Dickinsonian oracle on double-exposure and the shuttered light:

Let my first knowing be of thee
With morning's warming Light -
And my first Fearing, lest Unknowns
Engulph thee in the night -
(E. Dickinson, 1254)