I can't seem to take a picture with a Canon T3i Rebel in the dark. I want to take a picture at night with very little light around the subject, but the camera won't allow it in automatic mode. What can I do to make it work?
There are several reasons your camera might not take a photo in low light.
First, it may be too dark for the autofocus system to work. Most cameras have AF systems which work down to about EV -1, which is dim ambient light. (Your eyes will adjust and be able to see relatively well, but the camera won't work.) And, in turn, many cameras will refuse to take a picture without a focus lock. There are three solutions here:
Second, it may be too dark for the longest shutter speed allowed by your camera's auto mode. Options here are:
You haven't mentioned which lens you are using, but the standard kit lens, a 18-55 zoom, is very slow (small maximum aperture). It doesn't let a lot of light into the sensor system.
Both the auto-focus system and the main sensor require light to work. They dont' work in the dark. Unlike your eyes. You may simply need more light.
When I am doing low light work on a tripod, I use a small LED flashlight to help the camera focus. Press the shutter half way, use the flashlight, turn off the flashlight and press the shutter the rest of the way.