Quote Originally Posted by Mark Layne
Many people do not realize that the Biometer is in fact a Planar.
The Biometar is not a Planar; for that matter the Rolleiflex and Hasselblad versions of the Planar are not really Planars either, but modified version using five elements instead of six: a cemented doublet replaced by a single element. The Biometar is like that as well, but it has the back doublet turned into a single element rather than the front, which is similar to the Xenotar.