I have been fortunate to have done 4 landscape photography trips to New Zealand, 2 of those trips for 6 weeks each. Some of my favorites:
1. Routeburn Great Walk, which traverses Fiordland and Mt. Aspiring National Parks. A 3-day hut-to-hut backcountry hike. This is one of the most scenic tracks, mile for mile, that I have ever taken. If you do not have 3 days, you can do the start and the finish of the trail as day hikes. Key Summit is a short climb from the Fiordland trailhead and offers a spectacular vista.
2. Hump Ridge Track (a private track but reasonably priced). At the southernmost end of the island. Also a 3-day hut-to-hut hike, but you can do a portion of the first day's hike that takes you past a very wild and rugged beach.
3. Abel Tasman Great Walk. North end of the island. You can do a 4-day beach hike, or a 1-day ocean kayak trip, or anything in between.
4. Nelson Lakes National Park. Do a long day-hike to Angelus hut and back, as well as photos around the shore of Lake Rotoiti. 3000' up and down.
I have photos of these New Zealand destinations and more at http://www.sublimelightlp.com/f365913020
Enjoy your trip.