Most cameras develop defective pixels as they age. Defective red and blue pixels show true to color, but green shows as white. Bad pixels are a subject that camera manufacturers avoid like the plague. All cameras have problem pixels but the manuals and other publications avoid describing them, explaining terms, or noting specifications. Let us define some of the terms and explain some of the systems used in laymans' language.
Pixels show more as the camera warms up.
The camera under evaluation should be turned on at room temperature for at least 2 hours before measurement. With the iris closed, check for pixels at 18db. Use a video monitor with the brightness turned up enough to see the background noise. You will see all the defective pixels that the camera has. By switching gain between 9db and 0db you can determine whether or not the pixels are in an acceptable range.