Understanding color from photo to press
By Eric Olesh
Have you had images printed that appear nothing like the original? Or something that looked great off your inkjet printer looked all wrong when you had your promotional material printed? You are not alone. Many press reproduction problems stem not from technology, but a lack of understanding about color and printing technologies. Trying to achieve output that resembles the original can be extremely frustrating, even for graphic art professionals.
In the darkroom or on a computer, photographers tweak an image until it is visually appealing. Unfortunately, tweaking and retouching may do little to fix the real problem when it's time to go to press. In order to achieve visually pleasing reproduction, photographers must understand the process from input through print run.
Photography is the beginning of the input process. Printing is the output system. Whether film or digital capture, variables abound in the input phase. Different types of films and chromes use different film bases and dye solutions. Photographers manipulate image appearance through exposure, lighting and temperature, and a myriad of digital image adjustments. Moreover, labs all have their own combination of equipment, techniques and procedures for processing film and files.
Input devices can capture a broader tonal range than the printing process can reproduce. Tonal range, in reference to printing, means the amount of tones found between the highlight to middle tone of an image. The longer the highlight to middle tone range, the lighter the image will appear. This is also referred to as high contrast. On the other hand, a short highlight to middle tone range produces a low contrast or dark image.
Each of these variables will affect the final appearance of the printed product. Though the printer may have some idea of how the final print will look like according to their experience, there are no guarantees.
ICC color management provides the technology to help overcome these issues and produce excellent color press reproduction. ICC stands for International Color Consortium, an organization founded to produce a vendor-neutral platform to accurately produce color from one imaging device to another. This means a color reproduction system may be assembled with components from different vendors. In the past, if you purchased a scanner from Agfa, the rest of the equipment in the system had be Agfa to work properly. This is no longer the case; a RIP from EFI will work with a digital press from Canon.
With ICC technology, the color from the original image file or scanned image, the proof and the printed piece should all reasonably match, and not just in theory. The result should be a faithful representation that meets your color expectations.
Whether you perform the color work on your images or have an outside company prepare the image, it is important to understand that each imaging device in the reproduction system has color limitations. Digital capture devices and film scanners have a large color gamut, but printing presses have a much smaller color gamut. The printing company's proofer has a larger color gamut than the press. Therefore, the press can only reproduce a limited amount of colors. So there are two problems. The press has a limited tonal range as well as small color gamut. This makes it difficult for a press to match the tone and color of an original photograph.
RGB scanner gamut CMYK press gamut CMYK proof gamut
Despite these technical limitations, the hard copy proof should reasonably match what is printed on press. A printer that utilizes an ICC color management system should be able to produce a faithful proof-to-press match. In order to produce a quality image, the image should be color separated using a press profile. You can request an ICC profile from your printer if you wish to create a "soft proof" or separate images yourself.
The press comany uses a proofer profile to match the proofer color gamut to the press. The proofer has a much larger color gamut than the press. The proofer profile ensures that any un-necessary colors are clipped from the proofer to produce a good proof-to-press match.
CMYK press gamut and proofer gamuts
The illustration above shows the color gamut compression of the proofer to match the press.
It is important to understand not just your own discipline, but also the vocation of other areas. By increasing your education, you will be in a better position to work with others and ensure that your work is reproduced correctly. By being more knowledgeable you can better manage color issues and avoid preventable errors.
Eric Olesh is a Technical Marketing Analyst for Canon U.S.A., Inc. His credentials include a Bachelor of Science in printing management and sciences from Rochester Institute of Technology and certification in statistical process control.