It does not appear to change length when focusing, reviews are starting to appear but seem to be somewhat limited in scope so far - perhaps only including Canon approved topics?? , there's one here that reports working distance at 1x and 1.4x: https://www.the-digital-picture.com/Reviews/Canon-RF-100mm-F2.8-L-Macro-IS-USM-Lens.aspx Buried deep in the review it's 110mm at 1x and 85mm at 1.4x.  A couple of you tube videos show people using it up close and the lens has not extended wh