Having had a look at your Flicka acc. pics in the larger sizes, you do appear to have dirty sensor, there is no way you could focus on a filter and a distant landscape at the same time.
Polarising filters do not just give nice blue skies, they can remove sheen from a lot of surfaces (leaves etc.) to intensify colours. You could try when using a polariser just holding it in front of your eye, then attaching it at the same angle to your camera. Though not easy lining it up if it is a screw in one.
If you have a Lee holder and polariser it is fairly easy.
C
Polarising filters do not just give nice blue skies, they can remove sheen from a lot of surfaces (leaves etc.) to intensify colours. You could try when using a polariser just holding it in front of your eye, then attaching it at the same angle to your camera. Though not easy lining it up if it is a screw in one.
If you have a Lee holder and polariser it is fairly easy.
C
