Graphic files formats, why there are so many of them?

We frequently have people asks us “Why are there so many graphic file formats?” which usually means they are really asking “Why can’t there just be one format?” One format, would certainly be easier some of the time – but there are many more times when it would be very limiting.

Many digital cameras and web sites use the “Joint Photographic Experts Group” or JPEG or JPG format. The JPEG format is at its best when used for photographs and paintings with smooth variations of tone and color. For use on websites and email, where the bandwidth used by an image is important, JPEG is very popular if not the most popular.

The reason that JPEG is popular for website and email applications is because it has very effective image compression. Compression is the process by which less data is stored which makes the files smaller. The trade-off or risk is that if you store too little data the image will lose quality. There are two types of image compression – lossy and lossless.

Lossy compression methods usually can make the smallest and most efficient files. However, lossy compression, especially when used at low bit rates, introduce compression artifacts which means lower quality. With lossy compression method compressing data for storage and then decompressing date for display results in data that may well be different from the original, but is close enough to be useful. Lossy methods are especially suitable for natural images such as photos in applications where minor (sometimes imperceptible) loss of fidelity is acceptable to achieve a substantial reduction in bit rate. JPEG is the most popular and widely used lossy format.

But not every image is a photograph. JPEG is not well suited for line drawings, textual or iconic graphics, where the sharp contrasts between adjacent pixels are critical. Without those sharp contrasts line drawings, for example, will lose all their precision. Such images are better saved in a lossless graphics format such as TIFF, GIF or PNG.

With the understanding that JPEG is a lossy compression method, where some quality is lost after each edit, it should be obvious that this is not a good format for things like astronomical or medical imaging. In applications like medical imaging an exact reproduction of the data is not just required – but lives will truly depend on it. While you could use a lossless format such as PNG, the medical industry has created formats like DICOM ( which is a universal data format which allows storing series of images as well as much additional information about these images.

Lossy formats also risk losing image quality each time the image is decompressed and recompressed. So if you edit a JPEG file 10 times, each time while you make a change that matters to you (change a color, crop a section) you also lose some quality. To avoid this, an image that you expect to modify many times should be saved in a lossless format such as PNG. Then you can use ImageConverter Plus to make a JPEG copy for emailing or posting on a website. However, you still want to hold onto that PNG in case you need to make future edits.

Author: David Silversmith