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 largeJPEG 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
