Axiotron today announced that it has doubled the pen pressure sensitivity on its ModBook Mac tablet line to 512 levels, offering graphic artists, photographers and other users of applications such as Adobe Photoshop or Corel Painter twice the sensitivity and control of their pen strokes than any other TabletPC on the market, the company says. The upgrade is free and is being rolled retroactively into every ModBook order placed since its introduction, moving first customer shipments to May 2007.