For ease of use the A is better, set the aperture to "A" and it works like the current DA lenses but with manual focus only. However, the M is usually a lot cheaper.

Optically they're identical, the SMC coating may have changed but that's all.

If you want a 50mm it's also worth keeping an eye on auctions for the following cameras:

MV
ME
ME Super

The M 50mm f1.7 was a kit lens for these bodies and you can sometimes find a cheap lens if you're willing to give a camera body shelf room (or sell it on). You may also find the f2 version which isn't quite as good but still a solid performer.

Other bodies were also supplied with this lens but they tend to be more desirable, like the MX and late sales of the original K bodies (KM/KX/K2).

The same goes for the A 50mm f1.7 - a kit lens on Super/Program A, P30 series, P50, A3/A3000 and also some late ME Supers.

WR is Weather Resistant - these are the sealed lenses. They aren't waterproof (so don't take them diving) but are supposed to handle being rained on.

What they said about 3rd party copies. Much cheaper and perfectly acceptable.

If you want to buy genuine then make sure you get the hoods for the DA lenses rather than the WR versions, they are not interchangeable (WR hoods will not fit earlier DA lenses of the same focal length, at least the 18-55mm is like this).

It really depends what you want to shoot.

The 28mm lens is great as a replacement for a standard zoom and gives you a pleasing field of view.

The 50mm is longer, but popular as a portrait lens. I find it falls into a bit of a dead zone for me - too long for walkabout use but too short for long distance stuff.

If you don't mind stop-down metering then look for the Pentax 28mm f3.5, it's sharper than the f2.8 version. Pentax made two generations of the lens, the original SMC Pentax and a physically smaller SMC Pentax-M replacement.

Technically so long as your shutter speed is above 1/60 with this lens SR doesn't matter much. In reality as you have it you may as well use it!

I'm going to have to re-shoot this now...

I just bought a K 100mm f4 Macro after much debate and searching!

The red/green modes also support program flash. Try setting the flash to one or other of them and the camera to P. When the flash is charged the camera should flick to the correct aperture and set a suitable sync speed. Aperture will be dependent on what ISO you have set in this scenario.

You may need to try turning the flash and camera on and off a few times, mine doesn't always sync first time but once the two are talking it works reliably.

Given current weather I would expect one or more of the dams to be overflowing by this weekend. The Claerwen was in full flow last week. Unfortunately we never saw the remains of Nant Gwyllt or the submerged dam this summer.

I keep meaning to have a crack at a photo of the rapids on the way up to the Claerwen dam, it'd be a tripod and telephoto job as you can't really get that close to them due to the terrain but I often see people in the layby there aiming cameras so it must be worth a go.

I'm also waiting for Llyn Brianne to start spilling again. A lot bigger than any of the Elan Valley dams and with a spillway like a giant ski jump!

The Elan Valley is in Mid Wales. About 20mins drive for me so I spend a lot of time up there. I might well have been poking around the Claerwen dam on the same day judging by your description of the weather! I had a film KX with 35mm and 200mm lenses with me at the time.

It's also worth having a look around the turbine houses at the base of the lowest dam, you can't go inside but considering their purpose they're very elegant structures. The visitor centre still has the lineshafting and overhead crane from its time as the workshop for the dams too.

Pretty much all the dams have some interesting bits, even the Claerwen which is a late 1940s attempt to blend a much larger structure in with the "Birmingham Baroque" of fifty years earlier.

You can walk up to the far side of the dam you shot here to get some different angles - yours is one of the better examples I've seen, but I see everyone else taking that shot and find myself looking for something else! Leave the car in the parking area just after the hump-back bridge down in the valley and walk up to the dam, the paths are pretty clear and you can get some interesting 3/4 views from close to the dam wall this way. Those lumps of stone sticking out of the face of the dam once supported a wooden bridge for a crane, you can also see them on the lowest dam. Go on the right day and you can walk through the dam for a small donation, visiting the tower in the centre although it isn't terribly exciting inside (one big control wheel!)

When the water levels are lower some very peculiar-looking eroded rocks appear in the riverbed below the dam which can make for interesting arty shots. There's also an old brick-built railway bridge and the wonderfully named "Devil's Gulch" cutting through the rock if you walk along the old railway trackbed for a few minutes.