I am a newbie in using Manual Focus lens on DSLR! I have got 3 Pentax SMCs, namely the Pentax Asahi SMC M 40-80mm f/2.8-4, Pentax SMC M 28mm f/2.8, Pentax SMC F 35-80mm f/4-5.6. For the 40-80 and the 35-80, I have got no problems but with the 28mm, Sometimes I just can't get the focus right. I am using a 400D, so when I see the photos on the camera itself, its okay. But when I transfer to my computer, its rather blur. Any suggestions? Like any equipments that I need to buy? Thanks!