The Enhance Image Control Palette is a floating dialog that can be positioned anywhere on the screen. It provides the controls to adjust the levels and set brightness, contrast and gamma of the active image.
This dialog is visible when you are in Enhance Image mode (i.e. the Enhance Image button 
is down).
To show or hide the Enhance Image Control Palette, click View->Toolbars->Control Palette or press the 
button.
Levels
The levels tool is used to change the dynamic range of colors in an image or to stretch the image histogram.
The AutoLevels button 
makes Image Optimizer automatically calculate and set levels that will stretch the histogram to use the full dynamic range.
Press the delete button 
to remove changes made.
Drag the Shadow, Midtone and Highlight diamonds with the mouse to manually set the levels or use the edit boxes at the bottom left of the palette.
To work on the red, green or blue channels individually first click one of the colored buttons. To work on all channels click on the black button.
Use the equalization slider to spread the colors or even out the distribution of the histogram.
Brightness/Contrast/Gamma
The Brightness/Contrast/Gamma tool is used to change the brightness, contrast and gamma in an image.
Use the mouse to position the brightness, contrast and gamma sliders to the desired values or use the associated edit boxes.
Press the delete button to remove changes made.
To work on the red, green or blue channels individually first click one of the colored buttons. To work on all channels click on the black button.
Working with brightness, contrast and gamma