Generally, as a rule, images for the web should be saved as .jpg or .gif, and images for print should be saved as .tiff or .bmp
The JPG is probably the most common file format for storing digital images, especially on the web. It is ideal for images that use more than 256 colours, such as digital photographs.
When you save an image using this format, some of the data is lost because the file is compressed [compressed: Made smaller by squeezing together. ]. JPG files can be saved at various quality settings which are measured as a percentage of the original quality. The lower the quality percentage, the higher the compression rate; therefore if storage space is an issue, you should aim to save your JPG file at 30 per cent quality.
Below is a photograph that has been saved as a JPG and a GIF.
The many colours of this digital photo have been preserved through saving it as a JPG. It was saved at a 30 per cent quality setting and has a file size of 7kb.
When saved as a GIF using 32 colours, the image is quite patchy and some of the colours are missing. It also has a much larger file size - this time it's 11kb.
Like the JPG, the GIF file format is commonly used on the web. It is ideal for images that have large blocks of a single colour, and it can support up to a maximum of 256 colours. Unlike with JPGs, it is possible to alter the background colour of a GIF to make it transparent [transparent: Able to be seen through; clear. ]. This makes it possible to place it over other images or on webpages.
When you save an image as a GIF, you can decide how many colours to use - 256 colours is the maximum amount and 2 is the minimum (black and white). The fewer colours you use, the smaller the file size.
The table below shows a logo graphic that has been saved both as a GIF and as a JPG.
The logo uses only a few colours , so is ideal to save as a GIF. In this case, it has been saved using 128 colours and is 3.5kb in file size. When saved as a JPG at a 30 per cent quality setting, the logo is slightly fuzzy and dull. It is also bigger in file size, at 5kb.
A TIFF file is a suitable file format for both Windows and Macintosh computers, meaning it can be easily shared between computers. Just like a JPG, a TIFF file can be compressed to reduce the file size, while still maintaining a high degree of image fidelity. Alternatively, it can be saved without compression to retain 100 per cent of the original image taken - where each pixel is identical to the original image taken.
This is an appropriate file format for Windows users. It is used for general storage purposes - such as when images are awaiting editing - or as wallpaper for a Windows desktop. BMPs aren't really suitable for Macintosh computers or the web. BMP images are large files that require a lot of storage space because no effort is made to reduce the file size.