[luk32]

I don't think so. I think currently dark matter is considered rather low mass density i.e. doesn't bend light too much. Black holes would.

Think that you have the mass spread out over a whole galaxy, vs just the middle.

From infinity-like large distance it's the same, from galactic it would probably make a difference.

[pdonis]

> dark matter is considered rather low mass density i.e. doesn't bend light too much. Black holes would.

Not if the holes were spread out in a very large diffuse cloud around a galaxy. A single hole would bend light significantly, but the averaged effect of a huge diffuse cloud of holes around a galaxy would be basically zero (because there would be as many holes bending light one way as the other, so their effects overall would cancel out).