There are several tracks starting from the Tasman Lake carpark. For a quick view of the lake, head up past the Blue Lakes to a viewpoint on the moraine wall (approx. 15 mins one-way). There are good views of the lower Tasman Glacier, lake, and the mountains at the head of the valley. I like this spot for its views, but it’s not my go to place for photography.
For that I head to the Tasman Lake outlet (approx. 25 mins one-way). This location provides plenty of awesome foreground interest for photography, be it icebergs floating on the lake after a glacial carving event, a frozen surface in winter, or the water current where the lake drains to the Tasman River.