PSB No: P-0078

 

Page: 3 of 3

Midtones:

The values in a continuous tone or halftone image correspond to

 

the medium values in the range. Generally the values is between

 

30% to 70%.

Pixel:

A relative unit of measuring resolution. Pixel size is relative, due

 

to the output device. For example, a monitor pixel may be

 

different in size compared to a scanner pixel. Pixels can be

 

measured absolutely when fixed to another standard, like pixels

 

per inch.

Posterize:

To limit the number of shades in an image to create a highly

 

contrasted effect.

Screen Angle:

The angle at which halftone dots are lined up. As mentioned

 

earlier, newspapers commonly use a screen angle of forty five

 

degrees.

Smoothing:

An operation that softens the edges between adjacent tones.

Spot Function:

A procedural body in the Postscript language that defines the

 

shape of the halftone spot.

Subtractive

Colors that are produced by mixing inks or paints. The three

Primary Colors:

subtractive colors are cyan, magenta, and yellow. This process

 

reduces the amount of light that the human eye receives. The

 

absence of color is white (0%), while full intensity is black (100%).

 

This model is used in printing.

Threshold:

The selected gray level above which gray shades are converted

 

to white and below which gray shades are converted to black.

 

This is used to produce higher contrast or posterize images.