Re: What is the true image size?
If you are looking at the Document Size from the lower left screen pull down menu, then PS displays the actual size of the opened, uncompressed document. You can verify this by doing Image>Image Size and look at the image dimensions in pixels or from the Histogram palette if you have enabled Show Document Dimensions. The size id the Length x Width x 3 Bytes for an 8 bit RGB image (1 pixel per channel). When you save a file as a JPG the resulting file is compressed, the amount of which depends on which compression quality you chose (1 = smallest file size, lowest quality; 12 = largest / highest). The file also contains a block of Metadata (date, file info, etc). The only way to tell the size of the physical file on your hard drive is to right click on its icon and check the properties box or hover your mouse over the file to see the stored file size. The size of the file on disk will usually be many times smaller than the opened document in active RAM.