Using compression

The most common file format used for photographs and pixel artwork is JPEG. When you save a JPEG file you must decide how much compression to apply. If you plan on printing 11"x17" or larger, we recommend setting the compression quality setting to the equivalent of 9 or 10 (on a scale from 1-12, with 12 being no compression) as used in Adobe® Photoshop®.

Our experience and research has proven that setting the compression quality higher than 10 does not provide for any increase in quality, while at the same time it generates significantly larger file sizes.

Many users apply a compression quality setting lower than 9. Our evidence shows that this compression quality setting often results in artifacts, particularly on large detailed prints made from those files.

If you plan to only printing at smaller sizes than 11"x17", you should be able to compress with a quality setting of 8 with excellent results.

Adobe Photoshop Compression