When I first got my Samsung LN32D550 LCD TV, I was unable to get the shadow detail setting to have any effect whatsoever on picture quality visually nor measurably. It turns out this happened since I was using HDMI RGB color space. When I switched to the HDMI YCbCr color space, the control started working. However, this setting does not directly control very low-end gamma, rather it controls how the auto dimming backlight works. With the RGB color space, the backlight would only dim on a 100% blank/black screen. With the YCbCr color space the shadow detail setting can be set to trigger dimming in dark scenes (identical to CE dimming on older Samsungs in the service menu). The shadow detail control goes from -2 to +2, with 0 being default. -2 produces the most aggressive dimming in dark scenes while -1 is milder. This also explains why my blue luminance/saturation for the blue primary is so off (the blue test pattern has a very low APL, which triggers the dimming).
QuickView Gamut.pdf 160.3134765625k . file