JPEG (Joint Photographic Experts Group) is the most popular digital image format in the world. However, it is the most misunderstood digital image format. Computer users prefer to use JPEG because it compresses digital graphic so well, and still provide good qualities. The problem is, every time you save a graphic as JPEG, the compression process will throw some data (details) away. So, if you open a JPEG, apply some edit, and resaved the image, you will lose quality, and further degradation will occur, and if you open the image again and resave it again, even more degradation will occur. Therefore, if you must edit an image, then you need to save it in one of the lossless compression format (like Tiffs), apply the necessary edit, and then save it as JPRG. It is important to know that even if you save your graphic (JPEG) in maximum quality, some degradation will occur (Barely noticeable). Also it worth knowing that if you are saving JPEG from Photoshop, you will see no visual differences between the high, very high, and maximum quality settings, however, you will notice big differences in file size. Moreover, if you are using Photoshop to save your JPEGs for your web site, then use the “Save for the web” option as it will give you a smaller file size than using the “Save as” option.
It is important to know that different Raster base graphic applications will compress the JPEGs differently even if you use the same settings. If applicable, blurring a background of a JPEG image will help reduce the file size. Also, if you have to use gradients color, and have the option to choose between vertical or horizontal gradient, the vertical gradient will give you a smaller JPEG file size.
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I had no idea that visually there is not a difference between saving JPEG at high through maximum through Photoshop. This will save my students and myself a lot of space on our servers. I have also experienced the degradation of images as they are opened and saved over and over again. You brought up a great point of lossless files such as TIFF files and how they do not lose any quality. I have a hard time getting this through to my students. If you have any suggestions or lessons that showcase the degradation of JPEG images please send them my way.
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