Fill in the blank: ___ is the additional process required to create a continuous-tone photograph or other illustration requiring gradations in tone on an orthographic film or plate.

Aquatint is the additional process used to create continuous-tone effects in photography or illustrations on orthographic film or plates, involving resin, heating, and acid baths.

Explanation:

The additional process required to create a continuous-tone photograph or other illustration requiring gradations in tone on an orthographic film or plate is known as aquatint. This technique involves sprinkling layers of powdery resin on the surface of the plate, which is then heated to harden the powder.

Following this, the plate is dipped into an acid bath, which etches the areas of the plate not protected by the resin, creating a tonal effect. In the context of modern reproduction processes such as xerography, the continuous-tone image isn't directly applicable as xerography is a dry copying process based on electrostatics.

Its major steps include the charging of the photoconducting drum, the transfer of an image creating a positive charge duplicate, attraction of toner to the charged parts of the drum, and the transfer of toner to paper, followed by heat treatment and drum cleansing for the next copy. This process is utilized in laser printers.