Digital Imaging Basics
Computing Resources >> Tutorials >> Graphics & Multimedia >> Digital Imaging Basics

Introduction

Definitions of Terms

File Formats

Image Production

Image Size

Best Practices

Viewing File Info

Editing Images

File Management

Additional Resources

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Definitions and Terms

Resolution: Refers to the sharpness and clarity of an image, measured in terms of ppi and dpi.

PPI: (pixels per inch) Measurement used for images displayed on screen.

DPI: (dots per inch) Measurement used in printing images.

Pixel: A word invented from "picture element" - the basic unit of programmable color on a computer display or in a computer image.
- from http://searchsmb.techtarget.com

Megapixel: A megapixel (that is, a million pixels) is a unit of image sensing capacity in a digital camera. In general, the more megapixels in a camera, the better the resolution when printing an image in a given size.
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from http://searchsmb.techtarget.com

Lossy: A term meaning "with losses , " used to describe image file formats that discard data due to compression.

Lossless: A term used to describe an image file format that retains all the data from the initial image file.

RGB: (Red, Green, Blue) The color model for display devices (monitors, digital projectors, etc.) Each displayed color is determined by a combination of RGB.  

CMYK: (Cyan, Magenta, Yellow, and Black) The color model for printing. If you are printing something in color, be sure you have saved it in CMYK.

Bit-mapped (or Raster) images: Images that have data that describe the color of each pixel. Larger display sizes equal larger file sizes in this type of image. Bitmapped images cannot be rescaled without resulting in   "pixilation", or loss of definition in the details.   JPEG and GIF images are examples of bitmapped images.

Vector images: Vector images have data that describe lines and curves. These images can be enlarged and still maintain their smooth edges (not pixilated like bitmap images). Artists and designers will often work with vector images, and then "rasterize" the finalized version for distribution and display.   Adobe Illustrator files (.ai) and CorelDraw files (.cdr) are examples of vector images.

Proprietary: Denotes ownership and non-disclosure of details regarding format or programming code.   In the context of this tutorial, proprietary refers to file formats that require a certain software application to read/open that file.   For example, .psd is the proprietary file format for Adobe Photoshop files.

Open Source: Denotes a more accessible way to share, improve and distribute resources, requiring that licensing not be specific to a particular product.   See http://www.opensource.org for more info.


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