HD content (a Blu‑ray movie for example) is properly and commonly mastered with displays (such as Sony BVM‑D32) having 2.4 gamma, at 100 nt reference white, with about 1 lx ambient illuminance, and a surround of about 1 nt (that is, 1% of reference white, a “very dim” surround). The 2.4 gamma is specified in BT.1886, and is well approximated by a modern monitor whose black level has been properly adjusted with PLUGE.
A consumer television today typically presents reference white at 320 nt or 400 nt. In the evening, a typical living room is expected to have ambient illuminance of perhaps 100 lx (a few incandescent lights on), and a surround of about 20 nt (that is, 5% of reference white, a “dim” surround). In these conditions, a gamma of about 2.2 will yield an approximate appearance match to content mastered as described above. Modern consumer television receivers measure at around 2.2 gamma. (Computer displays are well described by the sRGB standard’s 2.2 gamma.)