So, just like making a photocopy of a photocopy, each time you open and save a JPEG, it will look slightly worse than before until it eventually loses all detail.įor this reason, JPEG is not suggested as an archival image format because if you ever need to open it and make edits again, you incur a loss of quality. JPEG images (with a few exceptions mentioned below) are lossy, which means that after the image is saved, the lost data can’t be recovered. This method is extremely efficient but comes at the cost of throwing away information you can’t get back. While the math behind it is complicated, this compression algorithm looks at the entire image, determines which pixels in the image are similar enough to the ones around it, and merges the pixels in tiles (groups of pixels that have the same value). To do this, JPEG relies on discrete cosine transform (DCT). A JPEG should have almost zero perceptible difference in quality, although this depends on the original image’s content and file type. If you start with a 10MB image and export it as a JPEG, you should end up with a roughly 1MB image. The exact ratio differs depending on the program and settings used, but the typical JPEG image has a 10:1 compression ratio.
