It will exist, but it won't be anything you will see without pixel-peeping. Perhaps the FX corners will show something easier to notice. The 24-70 zooms are usually at their best at the 24-35 range. The biggest gain will be that extra stop at f/2. If 35 is not a big deal, then why not look into a nice prime of 24 or 28? It will be worlds lighter, and certainly no worse.