One More Super Short Back Focus New Pentax Lens Patent (Super Slow Too!)

Last time I was surprised with the very short back focus distance of the new Pentax lens patent, but it is disclosed lately that it can be even shorter!

See: http://egami.blog.so-net.ne.jp/2012-06-13
(in Japanese)

For this optical design, it can work out a 18-70/3.5-7.1 lens or a 19-75/3.5-7.1 lens with some variations and for example. The shortest back focus distance at the wide side is now 2.17mm. However, the lens speed at the tele side is now at f/7.1 which is ridiculously slow, especially for the indeed low zoom power and short range of the zoom. It seems that Pentax is still wasting their already rather limited resources on something that is yet impractical, or even non-sense, I would say. Just imagine that the aperture and speed of such lenses are even slower than almost all P&S DCs'..