For scanning animation drawings for import into animation apps such as TVPaint Animation or ToonBoom Animate Pro / Harmony, or Digicel Flipbook you should seriously consider VueScan scanning software. VueScan (for Mac, Windows, and Linux) offers many options for image adjustment/enhancement . Scan your drawings in VueScan, then import to TVPaint (or ToonBoom, or Digicel Flipbook.
If your are using video capture instead of scanning then get iGlasses for Mac (Mac only, not available for Windows) . iGlasses gives you many more options for manually adjusting the exposure, focus, and white balance using an HD webcam (such as the Logitech C-930) . One more I should mention is a program called Webcam Settings , which is similar to iGlasses, for manually adjusting the image quality of webcams . (again, this is a Mac-only program. There are similar types of programs for Windows, but I'm on a Mac, so I don't have any recommendations. )