Please kindly advise me: I will be shooting landscape photos, from a moving bus or train. If I use a manual wide prime lens of around 12mm at around F/2.0, would I have most of the sceneries in focus and relatively sharp? Here is what I have tried: I went to Skagway/Alaska this summer and shoot landscape photos with an Olympus kit auto zoom 14-42mm at its widest F/3.5, from bus and train. In A mode, most photos were at iso 200 and got enough shutter speed to freeze movement. Almost all sceneries in sight were in focus. (Only some images came out nice, but) Image qualify is good enough for my casual enjoyment, though I did not pixel peep (like what I do with my macro/micro images). So I wonder, when I upgrade to a wide angle prime, do I need auto focus? If 12mm F/2.0 on m4/3 can record most sceneries in focus like 14mm F/3.5 did, that means that focal length+F/stop combo has enough imaging depth, such that auto focus is not critical, correct? If so, I may just save money by getting a manual wide prime, instead of buying the Olympus 12mm F/2.0 (which is around $500 new). Or does different sceneries have different depth requirements? This future lens will be used primarily on moving vehicles for sure, if that matters. When not moving, I can use in-camera focus bracketing of Oly E-M10 II, so imaging depth does not matter. If manual wide prime is good enough for my landscape application, please kindly recommend some of fast prime lenses wider than 14mm. Just no fish eye lens please. I currently only have Canon FD to m4/3 adapter, but don't mind getting other adapters. Budget is less than $200, preferably, unless nothing decent is available at that budget. Some minor CA and field curvature can be tolerated, though nothing too heavy please. As a reference, I can easily see CA in images produced by my Canon FD 200mm F/2.8 on m4/3 at high contrast edges, which is about the amount I can tolerate. Please kindly comment or correct me. Thank you very much.