I have a Sigma 17-70 2.8 Lens that I've been seeing some weird stuff out of -- wondering if it's broken or maybe if there is another issue. I noticed recently that when in Manual or Av mode on my camera, I can't select F2.8 as an option at 17mm. I can only get to F3.2. I started to dig around in EXIF data, and noticed that photos when the indicator on the lens says I should be at 17mm, it reads 21mm, and when I should be at 70mm, it's only reading 57mm. I guess my question is whether this a software issue or an issue or an issue with the lens. If it is something with the lens, is it worth having it sent out for work, or should I be looking for something different?