Here is an excellent article by Mr. Peter Zheng, very informative:-http://forum.xitek.com/showthread.php?threadid=655516(Text in Simplified Chinese, another reposted full version in Traditional Chinese can be found Here)The article contains all the essential details for the patents and optical designs used by various new Pentax digital lens models, namely, DA* 16-50, DA* 50-135, DA 10-17, DA 35
