21 scale step test.

One the essential parts of this process is determining the % of a black area of an image. That is to say that if you drag the color sampler tool in photo shop over your image and you find an area of black at 100% it means that the are is so solid that no light will pass through it. If we expose that to an ImagOn plate it will open bite, meaning that light won't got through the image it will form around the image. Since in intaglio printing we need ink to get into groves of the plate we need to open the dots of an image to a certain percentage that will allow just enough light to pass through the black areas to create the dot structure needed for that area to print black. You can see on this test where the 100 and 95% areas are washed away, they have open bit. The first line of black indicates the proper percentage needed.