Which Wide angle ?

Hi - we go round this quite often as its a popular topic. The Signa 10-20mm is the cheapest option (keep your eye open for 2nd hand deals).

Alternatively, a no-cost option would be to stich multiple shots together - free software such as Hugin or ICE allow you do this semi-automagically, although results can be somewhat bizarre sometimes, depending on how good your panning was...

your kit lens gives you a wide angle at 18mm this is wider than your 27mm compact.whether it is wide enough only you can decide. try comparison shots of the same scene. another is the tamron 10-24mm around similar price to the sigma . dont know about IQ between the two though but some body here will.

There is no conversion at all
A 18mm lens is 18mm no matter what camera you put it on since it's physical feature of the lens.

The angle of view does change when you move the lens on different formats.
If you're use to the 135format than an APS-C format would feel 1.5x longer.
The lens is still 18mm though but it behaves like a 27mm lens on 135 format and if you put the 27mm on the APS-C the smaller image will make it feel like a 40mm lens.

I hope it's all understandable what I wrote.

Actually, there is no way that a compact would start at 27mm for a wide angle! However, manufacturers often mark their lenses for compacts with focal lengths that are the equivalent of what they would be for 35mm film (or "full frame"). The 18mm of the Pentax kit lens should given an almost identical field of view to what your Panasonic calls "27mm".

If you want to go wider than either of these, you have the options listed by others here:

(1) take several shots and stitch them together in software. By the way, if by any chance you have Photoshop Elements, it already has the ability to do this (Photomerge) built in.

(2) Choose between the Pentax 12-24 (v good but expensive) or the Tamron 10-24 or the Sigma 10-20. I have compared the latter two and feel that although the Tamron is nice and sharp in the centre, the Sigma is much better towards the edges. The Sigma also feels better made. A secondhand Sigma in mint condition with all its original bits is likely to run to around £300. The Tamron is a more recent lens and you don't see them secondhand terribly often.

One other possibility is to buy a wide angle converter to screw into the filter thread of your kit lens. I think "Digital King" is a brand you see quite often, but cannot comment on how good the results would be. My expectation of putting more glass on the front of the kit lens would not be terribly high, however, and I suspect you would have lots of issues with edge sharpness, distortions, and lens aberrations giving coloured fringing. Perhaps others who have tried these converters can comment more?

Finally, Samyang have recently announced a 14mm prime lens. Their lenses are usually surprisingly good and decently-made as well as being exceptional value for money. I have not seen any reviews, but the website that may have one is called "LensTip". I'd expect the new Samyang to be around the same price, or cheaper, than the secondhand Sigma.

Hope this helps,

Jon

One thing to bear in mind with stitching software (which I use pretty extensively):

You need to use a lens with limited distortion for best results. I use an SMC Pentax 28mm f3.5 prime for landscapes now, and pan across the scene taking multiple shots with the same settings.

Yes prime means fixed ( not zoomable )