>> I'm wondering if it would be better to use 49 mm filters.
Personally, I'd use the 49mm; it's smaller and closer t the original filter size. Take some test shots with the polarizer. You can get some vignetting at some focal lengths with a standard size polarizer. Many use a "slim" polarizer for the FZ18 but they can be hard to get in that size.
Regarding the mountain lake scene you describe, the polarizer should help a lot. You could also get a color graduated neutral density filter. Here are some info and photos showing the results.
http://www.tiffen.com/color_grad_filters_pics.htmThings you can do when using the camera:
- Bracket
- Set it to -1/3 or -2/3 Exposure Compensation
- Use AE/AF Lock - if you haven't yet learned to use the AE/AF Lock button, it's well worth doing.
A summary of these techniques are here (follow the links):
http://www.digicamhelp.com/learn/toptips/exposure-tips.phpI use the focus/exposure lock and recompose technique very often. It is discussed here, with illustrations:
http://www.digicamhelp.com/taking-photos/basic-techniques/fe-lock.phpGenerally, it's better to slightly underexpose a photo for scenes like you mentioned. You avoid blown highlights, which contain no detail. When you edit, you can bring out detail in underexposed areas.