Originally posted by Lowell Goudge It is important to note that all the adapters here that are discussed, along with modifications to lens mounts etc, are for manual focus lenses.
As a result, you might just as well stay with legacy Pentax lenses. Avoid the pain iPod modification and have some fun at the same time.
BUT: There are lenses from other manufacturers that are, frankly, superior to Pentax optics of the same FL, and some are more readily available. I obtained a Nikon 600 f5.6 EDIF in excellent condition for under $1000. The 600 f4 Pentax is superior, but try to find one and wince at the price. I've never seen a Pentax 600 f5.6 for less that $2000, and the Nikon has IQ at least as good if not better. BTW: I use it with a no-lens adapter that does not permit infinity focus, but it's primarily a birding lens, so it is never used at anything close to infinity and the adapter permits a bit closer focus. I leave the lens @ f8 so it is used as you would use a 500mm f8 mirror lens. There's a slight gain in IQ over f5.6, but there's no detectable additional improvement at f11, and what is gained in DOF at f11 is offset by requiring a slower TV, critical with such a long lens and birds as a subject.