Big thank you to everybody who's replied so far:

Boni - I love the Atmospheric Sensing Platform, it gave me a good laugh!  :D  Haven't had time to check out the other links properly. And I think that including Poser DoF stuff here too is a good idea - other people may prefer it to postwork DoF.

hborre - nice concise explanation of the bright white bits in the renders I posted - thank you! That made the bit on p139 of the manual that I quoted click.

cedarwolf - great to know that I'm not going to be the only one getting something out of this thread.

aRtBee - your tutorials on other Poser stuff have helped me get to grips with things in the past. I'll be checking your atmosphere ones later today. many thanks!

bagginsbill - I tried a very similar search yesterday and got nothing, even with Google (posted on the Community Center forum about the problem). Looks like it's working today - your link is like a gold mine! :)

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident. And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU or something else.
*soon only to be available in two flavours -  DAZ and Renderosity