@EdBray
I was watching a video last night on digital exposure using the zone system and it said to expose for the midtones and check for highlights, since you can bring out shadow detail but you cant bring back blown out areas. This was done using the spot meter, to find your zone 5 tones (I think). I found it pretty helpful, it was called 'Perfect Exposure for Digital Photography'.
Sorry, that is a load of tosh, if you expose purely for the midtones then you will blow out your highlights, and if you think you can underexpose shadow detail you will not be able to bring detail back without suffering a lot of noise in those areas.
For a standard digital image you should expose for the subject and if the main subject is bright, meter for the brightest area in which you wish to retain detail and then increase your exposure by 2 full stops if the main subject is dark, then expose for the darkest tone in which you wish to retain detain and then underexpose by two full stops. if you need more than this 7 stop range then you need to use HDR to acheive it.
At the end of the day if the sensor only has a 7 stop dynamic range, unless you use HDR techniques 7 stops is the best you can get.
Thanks for the heads up with the book, but I used the zone system as it was intended for sheet film more than 20 years ago, and also taught photography technique for a number of years!
I know how to expose, and have on more than one occasion pointed members to
this thread which may help.
My apologies to petebarnes (OP) for going off thread as his image is superbly exposed under the shooting circumstances I doubt any better could have been acheived with a single exposure!