I have three copies of this lens. The Super Takumar 50mm F1.4, this lens has fungus growth inside the rear elements, giving it a dreamy quality when used at wide aptertures. Hey, soft focus lens!! The second one is the Super-Multi-Coated 50mm F1.4. This lens is in near perfect condition, takes super sharp pictures and the colour is very nice. Finally, the SMC 50mm F1.4. This lens has a small scratch on the front element, but does not affect the quality of the picture, at least not at any aperture larger than F8.
[Update on September 2, 2005]
I sold the Super Takumar 50mm F1.4, the one with fungus, and the S-M-C 50mm F1.4, but still have another S-M-C and SMC 50mm f1.4. These two lenses that I sold had served me well and produced some pictures that I will always treasure and cherrish. I will miss them and hope that the new owners will enjoy using them as much as I did.
Hi Sunny. I do not own a Pentax DSLR, although I probably would buy a used one in the future. The screw mount 50mm F1.4 will work with the *ist DSLR with a M42-PK adapter. For more information about working with manual lenses, there is a section in yoru manual regarding this.
Since I do not own an AF version, I can not tell you which is better, but I will bet that the AF version is optically better, since progress in lens design has advanced a lot in 30 years since the screw mount version.