The HT5550 puts out enough light to fill a good-sized screen in a large theater. On my 92-inch Stewart, I saw 117.2936 nits peak, .1736 nit black, and a native contrast ratio of 675.5:1 after calibration. This is without the iris engaged and the bulb on Normal brightness.
Using the iris makes a huge impact on the dynamic range. With no other adjustments, peak output is 100.9582 nits with .027 nit black, and a contrast ratio of 3733.8:1. If you’d rather use SmartEco instead of the iris, the values are 115.41 nits peak, .0809 nit black, and 1426.5:1 contrast.
Maximum output comes from the Bright picture mode where you’ll see 186.3182 nits peak, .0339 nit black, and 5488.8:1 contrast. Don’t be tempted by this high ratio. It comes at the expense of significant detail clipping in both highlight and shadow areas.
In HDR mode, the peak output is 106.7733 nits with a black level of .0252 nit and 4241:1 contrast. 3D signals measured through the glasses yield 13.2458 nits peak, .0048 nit black, and 2766.9:1 contrast. This is with the iris engaged and bulb on Normal power. 3D crosstalk is a scant .02%, completely invisible.”