Thanks for the suggestions
Live mode only appears so have shift and rotate options (it would be a battery hog using live mode all the time anyway?)
The playback down-button crop does work well, but apparently only on one file at a time(?), plus it creates new files for the cropped pictures.
This is my first SLR (previously used two Panasonic pocket cameras and a Nikon bridge camera, all set to output 16:9), and I'm still learning. But what I dislike about 3:2 on a 16:9 monitor is that the picture is small on screen during the first look through the pictures.
What I wanted to do (to avoid keeping a massive number of large unwanted RAW files) is:
1- View new JPEG files from the K-3 as 16:9 on a widescreen monitor (full screen).
2- When very good pictures are seen, move their same-filename 3:2 RAW files into a working folder.
3- Once all JPEGs have been viewed, delete the large number (for me) of unwanted RAW files, where the JPEG is already good enough.
4- Process the chosen RAW files in Lightroom (can also export to JPEG with a different resolution, e.g. 12032x8000 for interpolated 96MP, or 12032x6768 for 81MP if the RAW was 16:9 cropped!)
The best current option does seem to be to load the JPEGs from the K-3 into Lightroom, then crop them all as a first step before quickly viewing them all fullscreen. I will play with this
Thanks,
Paul