All the above are the same exposure from the camera, a Canon 1Ds, just resized down. The JPEG version should be very similar to what appears on the back-of-the-camera LCD screen. I routinely capture 2 versions simultaneously (a JPEG and a RAW). The RAW was then LINEAR-converted, dark-subtracted, flat-fielded and even a bias frame applied to yield the version at above top right, all in ImagesPlus. Note how very dark it looks. Simple ImagesPlus "Digital Development" yields the bottom left version. I then exported it to my usual photo-editor (Picture Window Pro) to get the final version at bottom right with a little bit of tweaking.

The simple, back-of-camera histogram contains a lot of information for those who know how to read it. On the next slide we explore this a bit further and detail how you can measure your skyfog directly with it, either into the common amateur-quoted Visual Limting Magnitude or more accurately in Magnitude per Square Arc-Second.