Born in darkness yet I am the death of it

I am born in darkness
yet I am the death of it.
I take the sun and turn it inward,
though I have never touched the sun.

I can see a face and miss the person,
see a stranger and know them at once.
I fail slowly, without pain,
and some who lose me still can see.

I am not only in the eye.
I live in the mind that reaches forward,
naming what has not happened yet,
believing in rooms it has never entered.

Two people look at the same sky
and see two different truths.
I am proof that light alone is not enough;
something behind it must want to look.

What am I,
that begins as a spark on the retina
and ends as a conviction in the heart?