I don't have a f1.4 but my Pentax-A SMC 50mm F1.7 is still more than adequate for achieving a lovely shallow depth of field and still pretty sharp. I've seen them on ebay for as little as £35 but Mine cost £60. Its truly a great lens and I would recommend as an alternative.

link

Pentax-A SMC 200mm F4

SMC Pentax-A 20mm F2.8

Pentax-M SMC 100mm F2.8 plus lens hood

Pentax-A SMC 28mm F2.8 plus metal lens hood

Pentax 50mm f/1.7 SMC-M

get them while their hot hot hot!