i stand by red dawn.
must not confuse the 2 terms.
light falloff vs vignetting
falloff occurs when lenses are used wide open... maximum apperture... and this is solved by stopping down the lens a bit... one or 2 stops... fall off is characterised by dark (but not back) at the edges of the frame.
vignetting occurs when a foreign object (filter mount or wrong hood) blocks the corners of the frame causing a black edge on the picture...the correct hood will never cause vigneting unless its mounted wrongly.