Dropout, all or none
Color or Greyscale dropout is a great tool for increasing accuracy of extracting data from forms. But a bad dropout is far worse than no dropout. Partially dropped out forms have the ability to confuse data capture technology. These forms are commonly called “Zebra” forms where portions of the form have dropout, performed correctly and other portions have the fields now outlined in black. If you have control of the scanning and this is the situation, you are better to turn off dropout, or improve it’s use.
It used to be the only way to dropout a form was to use scanner driven dropout. This approach was limited in colors that could be removed. Essentially what would happen is the scanner would be equipped with lamps of red usually. During scanning, the lamp would be turned on thus canceling out the red in the form. Because of this, it was important that printed forms used a certain type of red. If you have ever had experience with color matching you know it’s quite frustrating. Especially because the colors you see on the screen are not usually what is printed. Things have improved, now even scanners are using software dropout, where images initially arrive as color and algorithms then remove pixels of a certain color range from the document. This has created the added benefit with some scanners and software packages of being able to dropout any color, and multiple colors at a time. There are even some packages out there where you can drop out things like colored lines.
When dropout with any technology becomes difficult, it is when there are gradations on the form because of bad printing, color wear, sun or other damage. Because the software is looking for consistency with any dropout, it will avoid colors that don’t match the norm. This is often seen when the first half of a form is dropped out and not the second because of a color change mid document. There are tools that allow you to specify a threshold that can assist with this. This can be a very low threshold when dealing with documents where it’s one color and black text, but more complex documents with a low threshold can lose important data.
The biggest key to proper dropout assuming good form printing is to scan the document as quickly as possible, removing time for damage to possibly take place. Dropout is a great tool, but if you find that forms are partially dropped out, it is better for data capture accuracy that dropout is turned off and deal with the black and white form than to include it.