Lens resolution comparison chart?

[JBT]

How accurate is this chart http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=295&Camera=453&Sample=0&FLI=8&API=1&LensComp=374&CameraComp=9&SampleComp=0&FLIComp=3&APIComp=0 I was planning on getting the Sigma 50-500mm until I saw the results from this chart. The Bigma doesn't look like it did so well when compared to the others. Is there any other charts out there?

[Peter_Perfect]

Tried the site for other lens; Sigma 70-200mm f2.8 and the Tamron equivalent. Allowed me to set the chart for 400mm and 280mm on a 200mm max focal length. I would be VERY wary of the results this site is offering!