This option is available only if you have opened the JPEG Export dialog box by clicking the Save button in the Bitmap Gallery. If you select a JPEG in the Bitmap Gallery and click Save, you can select this option to save the JPEG file out again without it being re-encoded. This means the JPEG you save is an exact copy of the original file and has not been through the JPEG process a second time. You will notice that when you select this option, you cannot change the Quality setting.