WHAT IS THE BEST FILE FORMAT FOR PHOTO PRINTING?

Or JPEG (JPG) Images 101

Many photo software editing programs give you certain options when saving JPEG (or JPG) images. You can choose the "quality" or "compression" amount of the image as you save it. But what does this really mean?

The JPEG image format is a "lossy" image format. You save images in .JPG format when you choose it in a "File Type:" drop down box from a photo software program. Saving in the JPEG (JPG) format always attempts to pull some of the pixels that make up the photo out of the image. The quality and clarity of the photo are never improved using JPEG. Even saving a photo using the highest level (least compression) will still drop information from it, though the lost information will be in the brightest or least visible areas the human eye probably cannot see anyway. Opening a JPEG and resaving a JPEG will accumulate loss in the photo.

JPEG compression works by examining pixel brightness on a scale of -1024 to +1024. The compression (or optimization) works according to brightness - not by color. Compression is greater in brighter areas of the image (where changes are less visible) and less in darker areas. JPEG optimization uses a complicated mathematical formula that operates on 8x8 blocks of pixels.

TIFF ImageJPEG Image

The two images above look almost if not completely identical. But there is a larger difference only visible when resized (more about the difference between resizing and resampling here). The JPEG image has much less information. Below, the TIFF image on the left remains printable after resizing, whereas the image on the right shows the blocks of 8x8 pixels. JPEG optimization has taken information out, which becomes visible when resized 300% or three times the size of the above images:

Why is this important? Many people think that JPEG images - because they often look very good on web pages or in photo directories are good enough quality for printing. Remember though that JPEG was developed for use on the web, where file size considerations are very important. Before the web, graphic artists had little use for GIF or JPEG images because they needed high quality images for printing on paper media - not for computer screen presentation. So, when choosing which format to save your images to, consider what you are going to use the image for - if it is for printing, GIF or JPEG formats should be avoided, and TIFF or possibly PCX should be considered as better (less lossy) alternatives.

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