Here, we provide ‘best practice’ tips for using JPEG images in print production.
JPEG (Joint Photographic Experts Group), the body that created the standard for image data compression, is the commonly used method of “lossy” compression for digital photographic images. The format exploits properties of human vision, by eliminating information that is difficult to distinguish. The degree of compression can be adjusted which allows for a choice of size of file as against image quality. JPEG can achieve 10:1 compression with little loss in image quality. JPEG is the most common image format used by digital cameras.
JPEG compression works by grouping together pixels of slightly different colour values into groups with the same colour value.
When using the JPEG format for images intended for print production, bear in mind:
- High-resolution images can tolerate image compression much better than lower-resolution images.
- Re-saving images in JPEG format does not reduce quality further where pixels have not been edited. Pixels that have been edited will be compressed to the same degree as the pixels in the original image. However, re-saving images that have been cropped does reduce quality further.
- Saving an image at JPEG level 10-12 in Adobe Photoshop should result in no visible degradation of the original image.
- Images with lots of small detail compress less and conceal JPEG artifacts better than images with large areas of smooth tone.