There are several options in M42 land - Pentax did a nice Takumar 300/4 which you can pick up for £100 - £150 (example) or for slightly less there's the Russian Tair 3S (300/4.5) as supplied with the Zenit Photosniper kits (example).

Either would probably be an improvement image-wise over your Sigma, but neither are exactly lightweight options so only take them out after eating your Weetabix...

It's a very good and capable camera indeed. Some folk just have a bee in their bonnet because Pentax chose to make something that would actually sell instead of bankrupting themselves chasing the miniscule, irrelevant, loss-making "full frame" market. Take everything with a pinch of salt.

So did you lot all dress up as goths to blend in with your subjects?

I still use a couple of cameras that don't have any form of built-in metering so I still find having a light meter handy. As Don points out they're also useful for incident readings.

As for digital meters being easier to use; I'm not so sure. They certainly have more options but when I take my Rolleicord out I'm far more likely to have my ancient Ikophot in my pocket than my Minolta III - the Ikophot is simplicity itself, needs no batteries, is easy to calibrate and never seems to get things wrong.

Of course with digital cameras you can just keep experimenting and looking at the histogram until you get things as you want them, so I'd say external meters have probably had their day for mainstream use.

Playback Menu -> Playback Display -> Bright/Dark Area (options: On / Off)

When you say "red", do you mean the preview picture on the rear LCD of the camera?

The K-m (like most digital cameras these days) has an option to show you which parts of the picture are over / under exposed - by colouring them red on the preview. This option can be switched on and off in the menus. The areas of red shown on the warning aren't part of the actual picture file, so if you take the photos off the camera and onto your PC you'll see that they're gone.

This certainly isn't a fault, it's quite an important feature; but if you're new to DSLR photography it'd probably be better to start with it switched off and come back to it later once you have a few of the more basic controls under your belt.

Hope that helps.

Actually, I'll eat some of my words there: The 645 doesn't allow for mid-roll changes, the two backs are for different film lengths (one for 120 film, one for 220 film) - mea culpa!

Standard kit lens with several MZ series models - think of it as an old-school DA18-55. Nothing to write home about but not a complete dog either, quite capable at around f/8 and smaller apertures, not a particularly useful focal length on digital though.

On the plus side it's very cheap and easy to find! I've had three or four pass through my hands onto eBay and they rarely fetch over £20 (I only got £22 for a mint/boxed one).

I can't see it offering any advantage over what you already have to be honest...

You'll be wanting this page: link (password is "Pentax" - case sensitive).

The main advantage of different backs is that you can have different types of film loaded into each (say ISO100 colour slide in one, ISO400 black & white print in another, etc) and swap between them as neccessary - no need to finish a roll and no need for wasteage. It's something we take for granted with digital but almost impossible with 35mm film (unless you owned a Rollei 3003 like I did - selling that was my biggest photographic regret).

Still, my offer of £100 is always open...

I'll give you £100 to take them all straight off your hands. You don't want to be messing around with all that antiquated and heavy MF stuff so I'd be doing you a favour really...