INTRODUCTION TO DIGITAL

Steps of Digital Photography

• Step 1. Capturing Photographs(Digital, film, slides, negative)

• Step 2. Editing Photographs (Edit, manipulate with photo-editing program such as PhotoshoP)

• Step 3. Sharing Photographs (Print, e-mail, web, DVD)

GRAPHIC QUALITY: an overview

• Many factors affect image quality.

• Two factors that determine image quality are resolution and color depth.

– Resolution is the number of pixels per inch.

– Color depth refers to the number of distinct colors an image can contain

Image quality also dependent upon the equipment on which they are produced (scanner, camera) or displayed (monitor, graphics card)

RESOLUTION

• affects the amount of discernible fine detail in an image.

• Computer images are made of dots.

• The more dots per inch (dpi), the higher the resolution

RESOLUTION: DPI

• Used when printing - pixels are turned into dots per inch and counted by the spread over the paper.

GRAPHIC QUALITY: Resolution

• Printers range from 300 dpi to 2400 dpi(or more).

• On the computer screen, the dots arecalled pixels.

• Monitor resolution is usually around 72 –96 dpi.

GRAPHIC QUALITY: Colour Depth

The color depth determined “How much data in bits used to determined the number of colours in an image file”.

Colour depth is measured in bits per Pixel

• The greater the color depth, the more colors may be stored. For example:

GRAPHIC QUALITY: Colour Depth

– 1 bit

– 8 bit

– 16 bit

– 24 bit

– 32 bit

• The greater the color depth, the more colors may be stored. For example:

– 1 bit   2 colors

– 8 bit   256 colors

– 16 bit             65,536 colors

– 24 bit             16.7 million colors

– 32 bit             Millions plus extra information

• The greater the color depth, the more colors may be stored. For example:

– 1 bit               2¹         2 colors

– 8 bit               2⁸          256 colors

– 16 bit             2¹⁶        65,536 colors

– 24 bit                         2²⁴         16.7 million colors

– 32 bit                         2³²        Millions plus extra information

• The more colors per pixel, the larger the file size

GRAPHIC QUALITY: File Size

The higher the image resolution the greater the file size.

The higher color depth, the greater the file size.

GRAPHIC QUALITY: summary

File size vs Resolution vs Colour depth ?

• The more colors used, the more bytes are required to encode the image, and the more bytes required for an image, the larger the file to store the image.

• The higher the image resolution the greater the file size.

GRAPHIC FILE FORMATS

• A computer can save and interpret graphic images in a variety of formats.

• Some of the most common are:

– GIF (Graphics Interchange Format)

– JPEG (Joint Photographic Experts Group)

– TIFF (Tagged Information File Format)

– PIC (PICTure)

– BMP (bitmap)

– TGA (Targa)

– PNG (Portable Network Graphics)

GRAPHIC FILE FORMATS

Which file format should be used:

• Small images like icons and buttons: GIF or PNG

• Line art, grayscale (black and white), cartoons: GIF or PNG

• 24-bit color-depth lossless Image: PNG, JPG

• Scanned images and photographs: JPG

• Large images or images with a lot of detail: JPG

• Animated icons : GIF

• High Quality printing: TIFF

TIFF or TIF

• Good for master copies of images.

• Uses lossless compression which means when a TIFF file is saved, no image information is thrown out.

• This also means the files can be largebe large

JPEG or JPG

• JPG is the most common format for viewing images on the Web.

• JPEG images are small for fast delivery over the Web and are also the most common format saved in digital cameras.

• JPEG uses lossy compression

• Don't save JPG's over and over because the images get compressed over each other and lose significant amounts of image detail and information.

• High quality JPEG is often 1/10 the size of a TIFF.

FILE FORMATS

What's Your Output?

1.     Computer presentation (Power Point, Presentations, etc) 

  PPI/DPI : 100

  JPG for smaller file size

  BMP for better quality

  35mm Slide: 900x600pixels

  PPT Full Screen: 1024x768pixels

2.     WWW web page (FrontPage, HTML editing)

  PPI/DPI: 72

  GIF, JPG, PNG, new SVG

-       GIF used for clipart, logos, or text

-       JPG used for photographs

-       PNG good for saving images repeatedly

-       SVG smaller file size working with vectorimages

      3.     Laser Jet Printed (Desktop publishing, brochure, flyer)

  PPI/DPI: 200 to 300

  TIF or BMP

      4.     Material to be photocopied

  PPI/DPI: 200 to 300

  TIF or BMP

5.     High quality publication  (professional journal, published book)

  PPI/DPI : 600

  TIF OR BMP

6.     Large poster (20" X 24" or larger)

  PPI/DPI : 150

  TIF OR BMP