> Then you can't see it through this device either.

The documentary goes into more depth as to why it is possible to see subtle variations in lighting using the device, and why a simple camera obscura is insufficient.

Similarly, the documentary also notes that the scrollwork on the harpsichord in The Music Lesson exhibits lens distortion consistent with an optical system. And Tim's contraption intrinsically reproduced that same distortion, before it was consciously noticed.

I'd highly recommend watching the documentary; it's quite fun.