A surprising fact about aligning optical systems

When you try to align a fully-assembled imaging lens with respect to a camera or some other lens system, there is a misconception that a unique axis exists in the imaging lens, which you can then align with the axis of the next lens system (or the axis of a camera). This video explains why. The slides are available in this link: https://www.researchgate.net/publicat... (Sorry -- in the video, I said that the slides are also available on Figshare, but I forgot that I didn't upload them there. Rather, they are on ResearchGate in the link above!)