What is a JPEG/JFIF (.jpg)?
JPEG is the “Joint Photographic Experts Group”, which has developed a format called JFIF (JPEG File Interchange Format), which is usually saved as .jpg (or sometimes .jpeg on systems which support long filenames). The format allows for 24-bit color, but trades off a bit of accuracy to achieve compact file sizes. The JPEG studied what the eye actually sees in photographic images, and created the format to be more sensitive to those things to which the eye is more sensitive. The eye is most sensitive in the green region of the spectrum, and is more sensitive to small brightness chnges than to small color changes, so the JPEG standard keeps more of the green information and brightness level information, while skimping on the red and blue information. Also, since most natural scenes have many smooth transitions and few sharp edges, the format allows a little blurring to compress the data as efficiently as possible.
