Outcome 6.2 Scanning: Resolution, Halftones, and File Preparation for Print

LPI

Lines per inch; describes the frequency of a halftone screen in printing.

DPI

Dots per inch; refers to how many individual dots a device can place in one inch.

PPI

Pixels per inch; pixel density of an image at a given size.

Halftone screen

A grid that breaks an image into cells for printing, where dots change size to simulate tones.

Halftone cells

Cells in a halftone screen containing dots that vary in size.

Screen frequency

The frequency of lines in halftone printing measured in LPI.

Sampling theory

A guideline that suggests image resolution should be about twice the LPI for print quality.

Interpolation

The process of generating pixels based on the values of neighboring pixels.

Optical resolution

The true detail a scanner can capture, as opposed to interpolated resolution.

Moiré effect

Interference patterns that occur when scanning printed halftone images.

Bit depth

The amount of color information stored per pixel, influencing image quality.

Compression

The process of reducing file size, which can be lossy or lossless.

RGB

A color model using red, green, and blue channels for color images.

CMYK

A color model using cyan, magenta, yellow, and key (black) for print.

Effective PPI

The pixel density of an image relative to its size in print layout.

Descreening

A scanning technique to avoid capturing the halftone pattern from printed images.

File size

The amount of digital storage space an image file occupies.

Master scan

The original high-quality scan intended for editing and archiving.

Image PPI

Resolution of an image expressed in pixels per inch, important for print quality.

Effective resolution

The effective PPI resulting from the size in which an image is printed.

DPI vs PPI

DPI is related to printer resolution, whereas PPI relates to image pixel density.

Scan PPI

The resolution setting at which a scanner captures an image, influencing detail and file size.

Calibration

The process of standardizing a scanner to ensure consistent color and tone in scans.

JPEG

A lossy image format commonly used for photographs, not ideal for master files.

TIFF

A lossless image format widely used for print production, preserving quality.

PDF

A versatile file format that can contain images and vector graphics.

Scaling factor

A multiplier representing how much an image is enlarged or reduced in layout.