Adobe Photoshop LE Tutorial-28 
Adobe Photoshop LE Tutorial-28
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A digital image contains
a definite amount of data.
There are various formats that can be used to store digital image data.
Scanned images are usually recorded as *.tif files. These contain all of the data for that image. Bitmap *.bmp files are similar to *.tif files.
It is best to use these two formats to store your original image and to modify that image.
Each image has two sizes.
One is the size of the file in BYTES (k or mb).
The other is its physical size on your monitor which can be expressed in mm., cm., inches or pixels.
*.tif and *.bmp images have maximal file sizes for any image.
JPEG compression greatly reduces the file size of images & *.jpg files are commonly used as images on web pages.
However, JPEG compression also reduces image quality.
Consequently, you should use the MINIMUM JPEG Compression and aim for MAXIMAL Image Quality when you use JPEG compression.
Minimal JPEG compression can reduce a 5 mb file to a 1 mb file!
When you develop web pages for the Internet, you need to reduce the file size of the images so that the page will be transmitted rapidly.
Most people still use MODEMS and Phone lines to connect to the Internet.
Consequently, your web pages will take a long time to download if you use images that have large file sizes.
Converting an image file to JPEG format does NOT change the size of the image when it is displayed or printed.
We will now see how Photoshop handles image size.