3M of 640x480 mean that the camera's maximum quality is 3 Mega bytes at 640x480 pixels depending on the image taken, more colors means more file size of the image. An identical photo of the same image size, higher file size (kb) means more vibrant and less hard edges. A high quality 640X480 is around 300 Kb or more, Medium quality is around 65 Kb and low quality usually max at 50 Kb.