So Gilles took this screen capture of me:-

…so that we could examine how much of my screen – on a 21″ iMac G5 – was reflected in the window behind me, and visible in the Skype video window; the answer is not much, but it provides a hint:

If you squint at both images you can see a smaller version of the latter image as part of the reflected screen in the former one, notably the “notch” at the bottom-right of the cupboard space behind Gilles. I like to place my picture-in-picture window top and centre, which explains the dark “blob” on my screen, atop the row of cupboards behind Gilles.

You can also see the layout of windows on my iMac’s screen.

It’s far from perfect, but it’s amazing what you can find when you look…