Thanks. I think the cloud formation seen in #1 then more pronounced in #3 is generally referred to as 'wave cloud'. It was certainly forebidding. I was shooting in to the light and exposing for the cloud which makes the landscape rather under exposed. It probably doesn't matter too much in this context but I suppose I should really get to grips with RAW. It would have been much less of an issue with the GRD4 and its DRC which really does work and is a feature I miss on the GXR when there is such a wide light range.