Let’s take a simple example (no need to worry, things will get
complicated later, see The devil in the overprint and knockout detail). Suppose you have a PDF file with two
overlapping objects. Their fill colors are as follows:
| Ink | Background object | Foreground object |
|---|---|---|
| Cyan | 40 % | 0 % |
| Magenta | 0 % | 0 % |
| Yellow | 0 % | 60 % |
| Black | 0 % | 0 % |
The table below shows what will “normally” happen when this PDF file
is color-separated and printed.
| Knockout | Overprint | |
|---|---|---|
| Preview |
|
|
| Cyan plate |
|
|
| Yellow plate |
|
|
| Resulting color in the intersection |
 C: 0 % M: 0 % Y: 60 % K: 0 % |
 C: 40 % M: 0 % Y: 60 % K: 0 % |