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Maybe I misunderstood your concept of a halo. An extended bright object directly behind a black hold does indeed appear as a halo around the black hole. It's called an Einstein ring. An off-axis object appears as an arc, which may be duplicated on the opposite side. This can be interpreted in terms of time dilation, but you can't have it both ways. Light rays are bent towards the black hole if time slows down towards the centre, in which case the background image is stretched outwards. They are deflected away from the black hold if time speeds up towards the centre, in which case the background image is squashed inwards.
When astronomers refer to lensing, they are talking about an effect called gravitational lensing. Normal lenses such as the ones in a magnifying glass or a pair of spectacles work by bending light rays that pass through them in a process known as refraction, in order to focus the light somewhere (such as in your eye).
GoC - That is blatantly wrong! Black holes are gravitational masses. Please stop talking shite on my threadsLight will not be focused towards one's eye if it is being bent outwards, end of story.
Light bends away from a BH.