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
