Digital Photography
File Types
This section covers
the basics about various file types and how they affect you image.
The main two file types that are relevant to photography are JPEG
and TIFF. The main difference between the two types are the size
of files they produce and the quality.
Lets start with TIFF. This type of file is used when size is not important but quality is. TIFF retain all the information contained in the image and are for that reason used to keep maximum quality. TIFF files are best used for archiving images (e.g. storing them on CD) or when the file needs to be worked on and re-saved several times.
JPEG files are mainly used because they compress the information they contain into a smaller file and so making them much better for sending over the Internet and storing on web pages - more details in Images For Internet Use. This compression however causes a loss in quality. The higher the compression, the greater the loss. The images below show two JPEG files, each with a different compression.
 © Sam Goard |
 |
| JPEG saved in low compression, creating a 31k file. | JPEG saved and re saved several times with high compression, reducing the file size to 22k but note the distinct loss in image quality |
The other very important thing to remember about JPEG files is that they are, what is called, a 'lossy' file. This means that each time you 'save' a file, it looses more quality - the right image above is an example of a re-saved file.
It is a good idea to keep the original JPEG file in a safe place, making a point never to 're-save' it. It is OK to copy files, since this does not alter their content, and play around with the copies to achieve special effects.
To sum up... If you want to manipulate and change the file and need the very best quality than work with TIFF files. If you need to publish your pictures on the web or need to send them as email then use JPEG. Remember, you can always convert a TIFF image to a JPEG later on but you should not re-save a JPEG if you want to keep the quality.
Read
more about:
Pixel
Basics
Table
Of Resolutions
File
Types
Image
Manipulation
Images
For Internet
Use
Images
For Print