As the other commenter mentioned, if you're on a monitor, the effect isn't nearly as strong if you're shaking your head vs shaking a phone. It's still detectable, but I think that's because I know what to look for. If I didn't know what to expect, the effect is subtle enough that I don't think I'd have seen it. This was also from shaking my head in front of my phone screen. I think the size of the image will make a difference (where smaller is better).