Visual content	Issues for visual content	Image production	Image acquisition	Image manipulation	Image creation

In Photoshop, the simplest and most flexible adjustment is the 'levels' histogram (accessible via 'Image>adjust>levels'), which looks like this:

The black arrow on the left indicates the 'black point' and increases contrast by adding black if it is moved towards the centre. The white arrow on the right indicates the 'white point' and increases contrast by adding white if it is moved towards the centre. The grey slider in the centre controls the midtones, which become lighter when it is moved left, darker if it is moved right. The histogram should ideally show some pixels in the whole tonal range (as in this example).

You can selectively adjust levels in the separate colour channels by selecting them from the drop-down menu.

In Fireworks, all these adjustments are done via the 'effects' panel, and are able to be switched on and off. The functions are very similar to Photoshop.

If your image is has particularly high or low contrast, or if you have lost highlight and shadow details in your scan, it can be useful to adjust the levels histogram during the scanning process. Most scanning software has that option available, and this will give you a broader range of tones in your scanned image.

EXPLORE the levels histogram http://www.scantips.com/basics2e.html