The mistake or the error could be more interesting then the work of art itself, because it can give another point of view, meaning or analysis of the work itself.
In this case an error, such us the light entering in the tank, caused an unexpected, unreal "surreal" effect: a wave of light that propagate in all the film. The photographic montage represent the way in which light can spread in a small dark place as a wavelength. The Light seems to be the main subject of the work, but if we get closer, we notice that it hides a series of portraits, under the surface.
'The photographs which strike you most are those in which the very imperfection of the process as a matter of absolute rendering leaves certain gaps, a certain repose for the eye which permit it to concentrate on only a small number of objects.'
Delacroix, 'A brief history of photography'.