My friend, Katsuhiko Inoue, posted a video on YouTube where he can show the the Pulfrich effect with only changing the densities of the right view (without glasses). It can be observed here: Pulfrich 3D video viewable without Pulfrich Glasses - YouTube . It is best if viewed using a cross-eye method or viewer.

This video not only shows how it can be used for creating 3D effects in some videos taken with a single lens, but also why it is important to match the L/R densities in video taken with two lenses, since that might cause unwanted "floating" in horizontal motion, if the lens densities are mismatched.