I recently had a client ask me a great question on the use of 8-bit and 16-bit images in Photoshop, and how it relates to final production in print. The question was, “What’s better to submit for printing, 16-bit or 8-bit files?” Immediately, I realized that to answer this question intelligibly, I was going to need do a little research and chat with the experts on our prepress team. Now I fully understand that not everyone is a print geek like me, but I enjoy searching for answers to questions like these. Finding solutions to these types of questions ultimately make projects go smoother, and ensures that the final project exceeds expectations. For me, it’s the holy grail of print salesmanship.
While I won’t go in depth here on the exact definitions of 8-bit and 16-bit color depth, and color theory in this article, a good source for further reading can be found here. What is most important about the two file types is the amount of color information that each type contains. An 8-bit image contains a total of 16.8 million possible colors, while 16-bit image contains 281 trillion possible colors. The amount of difference in color information between the two formats is obviously significant. With the additional information, so comes significant increases in file size. When side by side on screen, 8-bit and 16-bit images appear the same. Today’s monitors only have the ability to produce a few million colors. What does all this extra information do for the graphic designer? So where’s the advantage? The answer is that the additional color information provides flexibility. This additional information allows Photoshop to create cleaner transitions, smoother gradients, cleaner filter applications and maintain resolution when cropping and enlarging. For image manipulation, designers should be working with 16-bit images when possible.
So how does this relate to quality print production? In the traditional four-color, CMYK process printing, we are limited to produce just over 16 million colors on a printing press, due to the limitations of the four color process color gamut. In other words, a recipe of cyan, magenta, yellow, and black inks, only allow us create so many colors. Using a file format intended to produce trillions of colors, is overkill.
My advice to my client was this. While you are manipulating and preparing your images at the design stage of your project, work within the 16-bit images. Doing so will allow Photoshop to create smoother and cleaner edits. When the editing is completed, and the file is ready for export, save the files back to 8-bit images. In most instances, you should not notice any change visually to the image. This creates a hi-resolution file with a significantly smaller file size that requires less time to process and store. The smaller file size also allows for less processing cost and time with our prepress department, without a compromise to image quality. Because the CMYK color gamut is limited, the submission of 8-bit images is optimal. The 281 trillion possible colors found in the 16-bit image is a BIT much.
Do you have questions in print? Submit your questions to firstname.lastname@example.org and I’ll answer them in future article.