Hmmm… not sure what to say then… I’ve been a Mac user for almost 15 years and I have never used Grab directly. (The tiff-only thing put me off) However, the Grab menu is incorporated into Preview, which I use frequently, and for almost all of the screen shots I upload to the site. (Preview gives me the option to do some light editing and convert into several formats.)
So, aside from starting in TIFF format, I use the same utility function (if not the app) and don’t have this issue. I can only guess that there is some lossy compression happening at some point in your workflow.
B
Build it strong.
Keep it simple.
Make it work.
(Leroy Grumman)