Playback brightness



I recently switched from an htpc running embedded Openpht (1.7) to a Pi 3 running the latest Rasplex (1.8). I use a projector in a room with a lot of ambient light during the day and got in the habit of turning up brightness during playback so I could see dark scenes. That option appears to be gone in Rasplex. Brightness adjustment is a very valuable feature to me. Is it hidden or disabled?