That error means the subject is too dark for the camera to achieve proper exposure. If you're shooting in Shutter Priority mode the error appears when the camera can not increase the aperture, meaning the lens is as wide-open as it gets. If the camera is in Aperture Priority mode the camera will keep increasing the exposure time until it reaches 30 seconds; at which point it maxes out. If you're shooting in Manual Mode you won't get the error, you'll just get a dark shot. I don't know how, exactly, Program Mode handles this situation.Hi just recently I tried taking a photo of a tree in front of a great sky and my camera said the subject was too dark although I could see through the lens it was blurry and taking a picture came up pitch black I did try my other lens and same thing any help appreciated