Information Technology

Images:

Types, Resolution and Techniques

it34200/unit3/formatsconventions.ppt

Digital Image Resolution• Refers to the number of distinct pixels that can be

displayed.

• The term "Resolution", when used to describe a digital camera refers to the size of the digital image the camera produces, and is usually expressed in terms of "megapixels" or how many million pixels it can record in a single image. The number of pixels a camera captures is called the camera's resolution.

• Eg, 1600 x 1200 pixels produces an image with a resolution of 1.92 million pixels and referred to as a 2.0 megapixel camera

• 5 megapixel image with dimensions of 2560x1920 pixels.

it34200/unit3/formatsconventions.ppt

Digital Image Resolution• In general more resolution means better print quality.

• It also gives you an advantage if you need to crop or to cut the image.

• Computer monitors display images at 72 ppi (pixels per inch), meaning that there are 72 pixels for every 1 inch of linear screen space you see on your screen.

• Therefore, if you have an image on the screen that is 720 pixels wide, it will take up 10 inches of linear screen space (72 dpi x 10 inches = 720 pixels).

• On a printer at 72 dpi the result will look extremely choppy and jagged.

it34200/unit3/formatsconventions.ppt

DPI, Printer Resolution• DPI is determined by your hardware, ie.

your printer• Dots Per Inch cannot be changed by the

user through image editing software. • Dots Per Inch has no effect on the size of

your printed image • Dots Per Inch does have an effect on the quality

of your printed image.

Sharing photos, email/web• original image, eg.3 mp is 2048 pixels x by

1536, >200% larger than the av. computer monitor is capable of displaying (assume the monitor is set to 1024x768).

• Need to resize that picture that will be completely visible on the screen (resolution) and one that will not take so long to send via email (file size).

• Done in s/w; resizing where the largest dimension is no bigger than 600 pixels.

How many pixels do I need for printing photos?

How many pixels you need depends on:

• How you will be using the photo, eg. Web or printout

• What size it will be printed

Image TypesBMP, Bitmap, suitable for illustrations,

logos, etc. and are not compressedJPEG, jpg, suitable for photographs, and

are compressedGIF, for buttons, bullets, banners, etc.

they are compressed WMF, vector image, used to store clipart

images for windowsTIFF, bitmap image used for high

resolution scanningEPS, vector image, to create illustrations