"Down to a sunless sea," he caps it quietly. Since he already knows Sirius and Remus are always like this, he's been taking notes for Q to refer back to. However, even with prior warning, Sirius and Remus are making his eyes cross, and a dash of Coleridge is a welcome distraction.
Severus has a blank expression on. He'd been intending to try the assessment, but weeks on end of testing--testing to show others not only the shape of the soul but what occurred to bring it to its current state--without even a possible treatment at the end of it? No. There may be a point to it for Q, but not for him.
I was thinking that rather than a special wavelength of light, there might be a special solution to develop the film in.