Gravitational lensing and missing mass

The mass of an astrophysical object can be estimated by the amount of gravitational lensing of another object that it causes. To arrive at the estimation however, one assumes the validity of the inverse square law of gravity, or equivalently an attractive $1/r$ potential. We show that the above, augmented by a logarithmic potential at galactic length scales, proposed earlier to explain the flat galaxy rotation curves, predicts a larger deflection angle for a given mass. In other words, the true mass of the object is less than its estimated value. This may diminish the importance and role of dark matter in explaining various observations.