One thing I've used to great success is to detect pixel density and bump up the font-weight for those users. CSS snippet:

  .co-m-text-light {
    font-weight: 500;
  }

  @media  only screen and (-webkit-min-device-pixel-ratio: 1.3),
    only screen and (-o-min-device-pixel-ratio: 13/10),
    only screen and (min-resolution: 120dpi) {
      .co-m-text-light {
        font-weight: 300;
      }
  }