This plugin will ensure your comp is not exceeding specified colors values. It will legalize those values and let you specify which should be the whitest and blackest color.

A tool that lets you know which part of your picture is too bright or too dark by pointing the bad pixels directly on your footage. Similar to the way zebra-stripping works on digital cameras.

This creates a random jittery motion in the Y axis. You can modify probability to make or less jitter, and the pos variable to define how large the jitter is.