The question is, WHY do you want to convert from jpg to tif? You'll only make a larger file with the same artifacts that were present in the jpg(if any, of course), you won't get an alpha channel and as far as I know no other benefits either. So... Why? :o) Is it to use a texture in P3 or something? That would be about the only reason I can think of.

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.