Electrophotography

Overview Object View Surface View Magnification Variations

Electrophotography Magnification

Image Structure 
All electrophotographic images are made up of small dots, however the pattern or lack of pattern, of the dots depends on two variables: printer design (analog or digital and variations within digital electrophotographic technologies) and toner type (dry or liquid). Most analog printers/copiers used dry toner that dusted the toner particles on irregularly, producing images made up of small dots with no regular pattern. However, some analog printers had a halftone screen integrated into the printer/copier producing images with a regular dot pattern. A weak pattern may be present from a copied original. Digital eletrophotographic printers/copiers use a halftone screen to break up the image in order to produce varying tonalities. Some black and white digital copiers/printers produce an irregular FM screen. Digital laser printer/copiers often produce fine parallel lines or a rosette pattern. Most digital presses produce images with a regular halftone screen pattern. Color prints exhibit a rosette pattern that is produced by the rotation of the halftone amplitude-modulated (AM) screen during printing; this technique is used to eliminate a disturbing visual effect known as a moiré pattern. Color prints use process colors of cyan, magenta, yellow, and black.  Some digital presses also include light cyan, light magenta, as well as spot colors such as orange and violet. 

Dry toner is composed of colorant in a thermoplastic resin that is dusted onto the photoreceptor. These dots appear rough and dusty and satellites are possible. Liquid toner is composed of colorant in a thermoplastic resin in a solvent that flows onto the photoreceptor as a liquid. These dots have smooth, well defined edges and no satellites. The dots are nearly identical to those produced in the offset lithograph process. However, individual pigment aggregates may be visible—this does not occur in offset lithography.  
This analog EP print is imaged at 10x, 30x, and 50x. The image is made up of small dots with no regular pattern.

This analog EP print is imaged at 10x, 30x, and 50x. The image is made up of small dots with no regular pattern.

This black and white EP print was made with dry toner on a digital printer. Notice the halftone pattern and dusty quality of the dots.

This black and white EP print was made with dry toner on a digital printer. Notice the halftone pattern and dusty quality of the dots.

This print was made with dry toner and imaged at 10x, 30x, and 50x magnification. The dots have a dusty quality to them.

This print was made with dry toner and imaged at 10x, 30x, and 50x magnification. The dots have a dusty quality to them.

This print was made with a laser copier using dry toner. Imaged at 10x, 30x, and 50x magnification, the dusty quality of the dots is visible. Fine parallel lines are characteristic of the toner deposits from most laser copiers.

This print was made with a laser copier using dry toner. Imaged at 10x, 30x, and 50x magnification, the dusty quality of the dots is visible. Fine parallel lines are characteristic of the toner deposits from most laser copiers.

This print was also made with a laser copier and dry toner. Notice the parallel lines and dusty quality of the dots.

This print was also made with a laser copier and dry toner. Notice the parallel lines and dusty quality of the dots.

Color EP prints made on digital printers have a rosette pattern. This is best seen with low magnification, usually less than 10x.

Color EP prints made on digital printers have a rosette pattern. This is best seen with low magnification, usually less than 10x.

This print was printed on a digital press using liquid toner. The dots are smooth and clearly defined.

This print was printed on a digital press using liquid toner. The dots are smooth and clearly defined.

Liquid toner EP prints can be difficult to distinguish from offset lithographic prints. Using specular light and magnification the pigment aggregates in the toner are visible in EP prints.

Liquid toner EP prints can be difficult to distinguish from offset lithographic prints. Using specular light and magnification the pigment aggregates in the toner are visible in EP prints.

The security code consists of small yellow dots in the margins of the paper. They are best seen with magnification and/or UV light.

The security code consists of small yellow dots in the margins of the paper. They are best seen with magnification and/or UV light.

Layer Structure 
Layer structure depends on the substrate. A print on an uncoated paper is a one layer structure consisting of the paper support with the image toner fused to the top. A coated paper may be coated on one or both sides with the image fused to the top. 
On coated papers, the paper fibers will be obscured. The image is fused to the coating.

On coated papers, the paper fibers will be obscured. The image is fused to the coating.

The paper fibers will be visible on uncoated papers.

The paper fibers will be visible on uncoated papers.