The 5D Mark III was first supported in Light room 4.1.
However Adobe no longer sells Lightroom 4 so if you really want LR4 you'll have to find it via a reseller or elsewhere. Beware of pirated copies.
Thanks John, I ordered the software from Adorama and I'm expecting it today. I did use a DNG converger, I found it kind of slow, maybe thats because of the file size.
I'm curious to see if the conversion files will look the same as the direct raw files I'm used to seeing in Lightroom. It'll be good to compare. While waiting I looked at the files in Digital Photo Professional and the files looked incredible. I was able to open one at a time in PS but in TIFF format. Not the most practical but impressive. I'm loving the D5 Mark 111
after one go at it.
You shouldn't see any difference at all. It's the same raw image data that was in the original file. It has just been copied to a new standardized container file with the DNG extension.