Hello, my name is***** to Justanswer! Give me just a few minutes to look up some specifics, I'm working on this now.
Have you tried different monitors with your cameras?
How about with USB? I want you to connect it to a TV using the yellow output. The yellow gives you 480p video, USB and HDMI will give you 1080p resolution. Since you have two of them, and they both do the same thing, I'm thinking it's a manufacturer defect. We'll have to grab the video another way. The USB will work with Windows Vista, 7, 8 & 8.1.
Did you try the USB like I suggested?
You do have USB, it's located right next to the HDMI terminal.
That is for transferring video to your computer. I want to know if the video is still dark.