CaptureScreen is easy to use:
Right-click for contextual menu access. Move and size the window to the desired location, and select the "Capture" command for a region capture of the screen, or the "Full Screen" command for a full capture of the screen. Save the capture with the "Save" command; png format (by default) gives a perfect result. The "Clear" command erases the capture.

CaptureScreen includes advanced options:
The "Thumbnail..." command allows you to save a thumbnail (or a enlargement) of the capture (with a Preview command). Image effects (Lighten, Darken, GrayScale, Invert, Contrast, Color, RGB ...) and special effects (Selective GrayScale, Color To Transparent, Psychedelic, B/W Sketch, Color Emboss...) are available with the "Effects" menu. The "Transparent Mode" command preserves the window and the image in transparency: you can use the capture like a tracing paper. The "No Border Mode" command allows you to hide window's border; you can open by example several instances of CaptureScreen to make a photomontage. The "CaptureScreen Options" allows you to set and save user settings (hotkeys for menus commands, transparency, exposure time...).