Assume a black hole has a mass at which light can only just escape it. Next the black hole reaches a mass precisely large enough to 'keep light in'. What happens to light at the turning point between those two states ? Is that the point at which light turns to matter ? (just a wild guess)
Light follows geodesics through space, which are curved towards the center of the object (black hole). If sufficient mass is not present where light is allowed to escape, it might appear redshifted from using most of it's energy to climb out of the "gravity well", perhaps so much it no longer appears as visible light. If it no longer can escape, it merely makes contact with the mass and transfers it's momentum to it. Three properties are still present in black holes; mass, charge and angular momentum.
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Imagine a normal black hole. Theoretically at exactly the event horizon, it's possible for a photon to orbit indefinitely. The photon would have to reach the horizon but never ever stray inside of it. Inside that radius, its orbit would decay and it would fall into the singularity. Outside that radius, its velocity would be enough for it to eventually escape. In any event, it's still a photon.
