Originally posted by robthebloke Maybe it's just me, but it seems to be a place for wide, long, or macro.
This is a very astute observation, for anyone at all interested in the natural world in Australia or NZ.
I think you really want something wider than 18mm, and preferably wider than 16mm - for NZ as much as for Oz. Take your 15 for sure.
I think you will be very frustrated if you don't have anything longer than 85, 100 or 135mm. Don't go to Australia for a holiday without a telephoto lens. The new 55-300 PLM would be ideal (with the firmware update in the K-3ii). I'd get it sight unseen for a trip, if I had a compatible camera, as you do. Failing that, the HD 55-300 WR (which at least has the advantage of being half a stop faster). If you only want to purchase one new lens, I'd prioritise that over a 16-85 or 18-135.
The light in Australia and NZ is generally good enough that you won't really need f2.8 zooms, unless you are going to shoot indoors a lot.
Don't obsess too much about WR for Australia/NZ (unless you are going to the tropical north of Australia in the wet season, or spending a lot of time in SW Tasmania or NZ's Southland). Yes it's useful but I'd suggest prioritising the appropriate focal lengths and IQ.
So my suggestion - assuming that you only want to purchase one lens - would be 15, 55-300 and one (or maybe two) of your excellent primes: FA 31 Ltd, DA*55, FA 77 Ltd and DFA 100. The obvious candidate there is the 31, but you could make a case for any of the others (e.g. the 55 or 77 for people, or the 100 for macro, WR and superb quality moderate tele), depending on your shooting preferences.
If you can't bear the gap between 15 and 31, you need to bite the bullet: leave them both behind and get a 16-85 to pair with 55-300.
And don't forget the polarising filter(s).