Nikon D3100 video shooting problem? - 1

For some reason when I shoot videos with my camera, they come out darker than it actually is and it's really hard to see anything.

It was never like this before and I don't know how to fix it. Does anybody know?

You are under exposed, you need to understand how exposure work, iso, aperture shutter speed.
http://www.cambridgeincolour.com/...posure.htm

You also need to know how to read an exposure histogram to help you nail the best setting.
http://www.cambridgeincolour.com/...grams1.htm
http://www.cambridgeincolour.com/...grams2.htm

Once you know how those work you'll be able to understand why your image is under exposed, you can 't judge the result from what you saw in the back-screen since those screen are brighter, it's the same thing when taking photography, you think the photo look good on the back then you import it on the computer to see it was underexposed, that's why you need to learn how things work, it will prevent you from having over exposed and under exposed results.