Those Damned/Great JPEGs

JPEG (Joint Photographic Experts Group) images - the ones we all use on the web - are a blessing because they compress regular digital images so much that they have made common use of graphic images on the web a reality. JPEG images are also a bane because they rob your images of their original quality by throwing away information that you'll never get back. What many don't realize is that each time you alter and save a JPEG image you lose a little more quality. Here's how I handle JPEGs.

Rule One. Save the image only once. By that, I mean make all your adjustments in the original (non-JPEG) format first. Routine screen shots are usually BMP or other bitmap format. Keep a copy of the original bitmap. Make your changes in size, etc., and then save as JPEG. Some programs let you select a quality for your JPEG. I usually use 7 on a scale of 1 to 10. Anything higher begins to defeat the purpose of JPEG, which is high compression and small file size.

Rule Two. For train sim screen shots, I usually sharpen the image before I save it. I use IrfanView (available free on the web - search for IrfanView). It has a batch conversion feature that lets me convert all my screen shots at once to JPEGs (while retaining the original format versions) and has a host of image adjusting features. Normally I just use the Sharpen function.

Rule Three. If your original JPEG is from a digital camera, it is probably a high quality image (9 or 10 on a scale of 10). If you plan to manipulate this image, you may want to save it to a more stable format, such as BMP or TIFF before working on it. Then save back to JPEG.

-- Al