Originally posted by schnitzer79 Maybe for the focus indicator you're right but as for the auto aperture,the lenses I've been looking at don't even have the A setting on the aperture ring.so for those,I guess aperture is manual
You guess wrong. The problem is that they use generic photos of the lens, not the photos of the lens for K mount. They show Nikon or Canon or Sony versions. You can see that it says NI or CA or something on the lens, denoting the lens mount - the Pentax K-mount lens will say KR on the aperture ring (K-Ricoh, I guess) and will have A setting. The Samyang 10mm, 14mm, 16mm, 24mm, 35mm, 85mm all have A mode on aperture ring, which means you can set the aperture on the camera body and that it allows Av, P and other automatic modes. For Canon Nikon and Sony mount, the lens allows different things because they have different technology. Sellers usually don't know anything, especially when it comes to Pentax K-mount. Just make sure the lens you are buying is "For Pentax" or "KR" and it should be fine. Pretty sure there are a couple threads about this, too. Oh, and Samyang also sells under other names, like Vivitar, Rokinon, Bower, Falcon, Walimex, ProOptic, etc. but the lenses all have the same optics and the same automation.
Exceptions to this are some Samyang telescopes and mirror lenses, which might have preset aperture mechanisms and are generally much lower in quality. These are 300mm and above
That being said, the 85mm f1.4 might be difficult to focus manually because the stock focus screen in modern DSLRs is not sensitive enough for such wide aperture. For best results, you might want to get a focus screen designed for fast primes. There are threads about this.
Also, you can go to a store and check the lens in your hand before buying it. If you buy online, most stores allow you to return the item in the first week or so.
tl;dr: modern Samyang lenses for Pentax mount (KR) have A setting on aperture and allow Av and automatic modes. Focus indicator and catch-in-focus will work, but only for central point. The lenses do not have AF, and they do not communicate their focal length to camera. Only Samyang lenses that do not have automatic aperture are the cheapo mirror lenses and telescopes.