Sat 29-Dec-12 12:13 PM | edited Sat 29-Dec-12 12:15 PM by ericbowles
With Auto selected and Auto ISO the camera is probably able to compensate for a stuck aperture. Check the images to see if aperture and ISO are actually changing with each image.
Try Aperture priority with a fixed ISO - not auto ISO. See if you can confirm that Aperture is not changing. Then try Shutter priority and see if the aperture automatically changes.
I'm pretty sure you have a stuck aperture in your lens. It is stuck at a narrow setting - probably all the way stopped down to f/22 which is why everything is dark. Normally the viewfinder is bright because the aperture wide open for focus regardless of your settings.