At that price for an ultra-wide it seems like a good deal even if AF is dodgy, as long as you can focus it manually with good results. You won't find many other options at 12mm.

I have a 6D, so a bit newer than a 5D II, but it has AF fine-tuning so I would imagine the 5D II would too. Maybe it's just that? My Tamron 28-75/2.8 focused badly on the 6D but the other Tamron and Sigma lenses I've tried on it are fine, if slower and noisier than the newer Canon lenses I have.

The Sigma EX 105/2.8 macro is a really excellent lens and that's a great price for one.

By the look of that image the lens is a keeper. There's nothing better than a great fast fifty on FF.

I've never heard of solenoid failure on the K200D. The K200D predates the dodgy solenoids used in later entry-level cameras.

If the photo has the same settings as the next, which is properly exposed, then either there is some failure in closing down the lens (easily tested by shooting wide open) or the shutter is slow.

I've only ever used Microsoft's free ICE program for stitching. It works fairly well with the occasional glitch but for some reason has now been removed from official download, though it can still be found. This may be a good alternative.

I don't think Canonites are any more likely to be shooting Pentax lenses than any other brand of mirrorless. On DSLRs yes, but not on mirrorless. All adapters are equal and modern mirrorless cameras I believe have very similar manual focus tools, allowing precise focus with any lens.

I moved from my main camera system being Pentax to Panasonic (S5) a couple of years ago and have refrained from posting anything from the S5 even when using it with Pentax lenses (which I do often). I still own and use my K-3 and Pentax film cameras so I'm very much a Pentaxian and still hang around here for news, chats and classifieds. I'm happy with whatever is decided but FF mirrorless has opened the door to Pentax lenses for a great many people who might contribute here and there are some FFM users who use nothing but adapted manual lenses. Sometimes I'm amazed that the prices of used Pentax lenses haven't gone up with all the FFM users.

Another vote here for using the genuine ones. The first time I tried a third-party one, in a camera shop, it got stuck on my K200D and their technician had to remove it. That kept me away from M42 lenses for a couple of years before I got a genuine one which worked without problems. I have several now, all bought used, and I don't think any cost me more than 20 quid.

The nail on the left forefinger un-clips it to remove it from the camera, holding the camera in the right hand.

The S5 has been my main camera for a bit over two years now and it is fantastic. The 20-60mm is also extremely good, without doubt the best kit lens around. It pained me to go outside Pentax but on the plus side it makes a superb base for using my many Pentax manual focus lenses as the manual focus tools are so good.

Always glad to hear of people enjoying fine manual focus lenses.

I'll add a comment on the AF lenses - maybe you just don't have the right AF lenses for you. It sounds like you want a 50mm and little else but have been drawn into buying some lenses you don't need. I'd recommend a 35mm lens for the DSLRs and leave it at that - there are a few to choose from, my favourite being the 35mm f/2.8 DA Limited but have a look and don't be hasty.