Digital Photography File Formats Explained

Introduction to File Formats

Your digital photographs won't be much use to you if you can't get them onto your PC or share them with your friends. For this you will need to know a bit more about the different image file formats in use.

Your camera needs to save the data about your photograph in a format that can be read and used by your computer and other devices. A file format is the method used to store the data contained in your images. Basically it handles how your photograph is stored, and allows your computer to know how to display the image after it's been downloaded from the camera..

There are lots of image file formats in use today, but luckily you don't need to know them all. We will focus on the most popular and widely used formats: JPG, TIFF, GIF and RAW. The ideal file format to use will depend on what you want to use the image for. Some formats are better suited to certain tasks than others.

File Formats:

JPEG: JPEG (pronounced "jay-peg") is short for Joint Photographic Expert Group. This is the most widely used file format for storing digital images. Most digital cameras use this format to store the photographs you have taken.

JPEG files are compressed to save storage space. Due to the compression it is considered a lossy file format. That means that when you save an image in JPEG format some of the image data is lost. This is not a big problem because the JPEG file format is very good in retaining all the information the human eye can see. Most people won't even be able to notice the difference.

TIFF: Tagged Image File format. The TIFF file format is very popular due to it being a relatively lossless file format. TIF files can be saved with or without compression. With compression it retains a very high degree of image quality while slightly reducing file size. Without compression it preserves all the information about every pixel in the original image, making it a 100% lossless format at the cost of larger file sizes.

GIF: Graphics Interchange Format. The GIF file format is also a very popular image format for use on the Web. It has a few benefits over the JPG format, and in general is more widely used for smaller images on websites.

The GIF format allows you to save images with a transparent background allowing them to be used on websites with backgrounds. GIF images can also be saved in interlaced mode making it very suitable for use websites. This allows parts of the image to show while it is busy downloading, giving your visitors an impression of the general image before it's fully downloaded.

BMP: Bitmap is the old standard image file format for Windows. It's not a very popular image file format due to its very large size. BMP images are also not used on the Internet and in general are not readable by Macintosh computers.

RAW: Some high-end digital cameras allow you to record images in RAW format (also called CDD-RAW). RAW format stores all the data from the CDD with minimal or no processing. You can then later process the RAW files to JPEG or TIFF format using your PC. Processing your own RAW files allows you much more control over your images and results in higher quality images.

You can tweak the various setting such as exposure, saturation, brightness etc. when processing your RAW files without losing any data such as you would if you did the same corrections with the JPEG format. This allows you the most control and results in the best quality images.

The RAW format does have drawbacks though. First you will need a special program to be able to process the RAW files to the other formats that will be viewable by other people. RAW files are also much larger than normal JPEG files (2x - 6x) limiting the amount of photos you can take. If you have a large memory card though, this shouldn't be a problem and the added control and quality is well worth the effort.

Which format to use?

In general the JPG format should meet most of your needs, and you wouldn't have to use another file format. However if you are planning to edit your images it might be a good idea to first save your files in a TIFF format for editing.

With JPEG each time you edit the image and resave it the JPEG compression algorithm is run on the image. This leads to a loss of data each time you resave the image. If you repeat the process several times you will see a significant loss in quality and sharpness.

With TIFF this is not the case. As explained earlier the TIFF format retains all the quality of the image, no matter how many times it is saved. You can edit and resave the image as much as you like without losing any of the quality.

TIFF images tend to be larger in size, so after you have finished the editing process you can always save the image as a JPG again making the file size smaller for easier use.

The RAW format should be used if you want absolute control over your images. Most professional photographers shoot exclusively using the RAW format due to the higher quality images produced. If you don't mind the larger file size and extra time spend processing RAW images, you should definitely give it a try.

Use on the Web: JPG and GIF images are the best formats to use for websites and e-mail. You can specify the quality of the compression when saving the images. You need to find a balance between image quality and file size. Most likely you can compress an image quite a bit without degrading the quality of the image too much. The higher the compression the smaller the file size will be, making it much faster to download over the web.

Prints: JPG should fit most of your needs for making prints. Higher quality JPG formats are the best option for retaining quality. Seeing as file size isn't much of a concern you can easily use the largest quality JPG format.

If you are planning on editing and resaving your images before printing them, remember to save them in the TIFF format to prevent quality loss during the resaving process.