I went out shooting this afternoon with my Sigma 17-70 f/2.8-4 OS to test it out after getting the AF adjusted to correct a severe rear focus issue I was encountering. It turned out I’d accidentally reset my D90 from RAW to JPEG and when I went to edit the images in Lightroom 3, I discovered that it couldn’t find a matching lens profile. A quick Google search led me to learn that the list of available lens profiles differs when editing a JPEG vs one of the RAW formats. I went back and checked some images I’d taken earlier and sure enough, the profile appeared.

So, for anyone else who is wondering … Several of Sigma’s lenses can be corrected in Lightroom only when you shoot in RAW. Apparently on a Windows 7 PC you can find the list of lenses supported in RAW at the following location:

C:\ProgramData\Adobe\CameraRaw\LensProfiles\1.0\Sigma\Nikon
(replace Nikon with your camera body manufacturer)

Source: Lightroom Forums – Lens profile – Sigma 17-70 F2.8-4.5 DC Macro