Hi Rob.Blaze,
Just to note, holding down the Control key does nothing extra. Command
Shift4 is all you need. One thing on that which
is extra, after pressing Command
Shift4, then press the spacebar and you can take a shot of any window without having to draw a marquee around it.
The default file for screen shots is PNG (Ping). It's nowhere near as bad as JPEG, but is still a lossy, compressed format. To change that choice, download and install
OnyX. Make sure to grab the right one as the author has different downloads for Tiger, Panther, etc. Run the app and click on the Parameters tab. You'll see a drop down menu about the middle right for "Format Screen Capture:". Change it to TIFF to get a lossless format.