With the explosion of scanners, digital cameras and the internet, the JPEG image format has quickly become the most widely used digital image format. It's also the most misunderstood. Here's a few common misconceptions and facts about JPEG images.
JPEGs lose quality every time they are opened and/or saved.
False. Simply opening or displaying a JPEG image does not harm the image in any way, but some image editors do recompress JPEGs when the 'Save As' command is used. To avoid more loss you should duplicate and rename JPEGs in a file manager rather than using 'Save As JPEG' in an editing program.
JPEGs lose quality every time they are opened, edited and saved.
True. If a JPEG image is opened, edited, and saved again it results in additional image degradation. It is very important to minimize the number of editing sessions between the initial and final version of a JPEG image.
JPEG is an all-purpose format suitable for just about any image.
False. JPEG is best suited for large photographic images where file size is the most important consideration, such as images for the internet or email. JPEG is not suitable for most small images under a few hundred pixels in dimension, and it is not suitable for screen shots, images with text, images with sharp lines and large blocks of color, and images that will be edited repeatedly.
JPEG is ideal for long-term image archival.
False. JPEG should only be used for archiving when disk space is the paramount. Always keep a master copy of any image you expect to edit again in the future.
JPEG images don't support transparency.
True. You may think you've seen JPEGs with transparency on the web, but in fact the image was created with the intended background incorporated into the JPEG in such a way that it appears seamless on a web page with the same background. This works best when the background is a subtle texture where seams are indistinguishable.