Articles related to correction
A Paint Thickness Gauge (often abbreviated to PTG, and also called a Paint Depth Gauge) is an electronic device that measures the distance between the body-panel and the sensor. This way you can measure the thickness of the paint. This gives you an indication of how much paint you have left to work with.
Holograms are a visual sideeffect that can occur when polishing in a certain way with certain products. It looks good with minimal lighting, but when the lights hits the paint just right, you can see certain marks in de surface. These are very small surface imperfections that cause the light to be reflected in a slightly different way.