Overview of Various Image File Formats
There are many different image file formats in use on Web pages today. Each file format has its advantages and disadvantages, and can be used for specific images. For those that use digital cameras you may be familiar with one format, while you may have heard of others.
In this post I will provide an overview of the different formats including their advantages and disadvantages.
I will begin with one of the oldest formats in use on the Internet today. The GIF name is a acronym for Graphics Interchange Format, and was first introduced by Compuserve in 1987. This is a popular format next to the JPEG format and is still used on Web pages today. Digital cameras, however, don’t use this format because it only supports 256 colours.
There are currently two versions of GIF in use: GIF87a (the original version) and GIF89a. The GIF89a version supports multiple images in stream which allows you to create animated GIF images.
Advantages – One advantage to a GIF is that it uses lossless compression to make an image smaller. This means that no image information is lost during compression. It also has the advantage of making one of the colours in the image transparent to allow the background to show through. As mentioned earlier, you can create simple animations by combining multiple images into a single GIF89a file.
Disadvantages – The biggest disadvantage for the GIF file format is that it only supports 256 colours, which isn’t nearly enough for a digital photo. This means that GIF files are restricted to sharp-edged line art (such as logos) that have a limited number of colours.
This is perhaps the most popular file format used for digital pictures, especially now that all digital cameras store their pictures in this format. Similar to GIF, JPEG is also an acronym for Joint Photographic Experts Group. This group was first formed in 1986, issued a standard in 1992, which was approved in 1994.
Unlike the GIF file format, the JPEG format can compress images that contain up to 16.7 million colours. This is more than enough for a digital photo. Besides the number of colours, another difference between the GIF format and the JPEG format is the type of compression used. While a GIF uses a lossless compress, a JPEG file is compressed using a lossy compression algorithm. This means that each time you save a JPEG file, it loses more information.
Digital cameras may also have the ability to save a picture in the RAW format. This format, however, is a proprietary format that is different between cameras manufacturers, so it isn’t used at all on the Internet. For more information about the JPEG and RAW file formats, please read JPEG or RAW Format.
Advantages – The biggest advantage is the ability to save a digital photo in a very small size (in bytes). Another advantage is that it can save an image that includes up to 16.7 million colours, which is more than enough for a digital picture. It is a very popular format for those two reasons alone.
Disadvantages – The biggest disadvantage is that the compression used in a JPEG image is lossy. Each time you save a JPEG image, the more data you lose. Another disadvantage is that if you compress an image too much, you will get JPEG "artifacts". These look like distorted sections of the images, usually looking like squares. You should minimize the amount of compression of the image, while at the same time managing the size of the file, to reduce these artifacts.
As with many names in the computer world, the TIFF name is also an acronym. TIFF is short for Tagged Image File Format. This a very popular format for archiving digital photos, mainly because it is widely supported by most image editing programs across many different operating systems.
Similar to the JPEG format, it supports 24-bit (16.7 million) colours. You can even save up to 48-bits of colour information within the file. The trade off is the file size. While JPEG files are compressed, TIFF files are generally uncompressed, which results in very large file sizes. You can, however, compress TIFF files but not to the same size of JPEGs.
Advantages – Since the TIFF file format is supported by pretty much all image editors on many different operating systems, it is the first choice for archiving digital photos. Since TIFFs don’t use compression, at least by default, you can continuously save a TIFF file and never lose any information. When editing photos, it is best to first save the file in a TIFF format during editing, and then JPEG once your are finished.
Disadvantages – The biggest disadvantage for a TIFF file is the size. Compared to JPEGs, TIFF files are enormous. Depending on the bit depth (24 or 48) you are talking 100MB+ for a single file. Although, with the size of hard drives and DVDs it will be worth it to save your photo archives in the TIFF format.
Rounding out the acronym file names is the PNG format, or Portable Network Graphics. This format is similar to the GIF format in that it uses a lossless compression. Years ago there was a patent issue with the compression used for the GIF format, so the PNG format was created to avoid any patent issues. This format is fairly new compared to the other formats since it was introduced in 1996.
One advantage the PNG format has over a GIF is the number of colours it supports. The PNG format supports 24-bit or 16.7 million colours. This means that it can be used as a format for your digital photos. The JPEG format, however, still compresses the file to a much smaller size, and has more support by image applications.
Advantages – One advantage that the PNG has over a GIF is the number of colours. It can support 16.7 million colours, which is the same as a JPEG file. It also uses a lossless compression, which means that you can save your image many times without losing any information.
Disadvantages – Since this format is new compared to the others discussed in this post, it doesn’t have the same amount of support. The older Web browsers will have trouble displaying a PNG image, but the newer browsers should have no problem. Although it can compress a 16.7 million colour photo-quality image, the JPEG file format can still create a smaller file size. If you do want to print your photos from a PNG format, ensure your photo lab supports the PNG format.
In this post I discussed the most popular image file formats in use today. Each format has its advantages and disadvantages and is suited for specific types of images. Some images are also suited for specific tasks, such as printing and archiving. The formats discussed here can be edited by most image editing software without any problems.