Earlier today, when my wife sent me an iMessage, I invoked Siri to send a reply for me. As soon as Siri heard my reply, the screen brightness went down to near 0% where I could barely see anything. I told Siri to send the message and still the screen was barely visible. I tried to adjust the brightness but it was just too dark for me to see. When my wife replied to my message, the screen returned to its original brightness level. I wonder wondering if anyone else experience this issue also. This was on the iPhone 5 with Auto Brightness disabled.