An ICC color-managed workflow is essential for proper color handling. This workflow is based on colorimetric matching. In fine-art reproduction, appearance matching must also be considered as a further refinement to the ICC workflow. Practically, this means the image must be considered as a whole and within the context in which it will be viewed. Some appearance matching issues to consider include:
- When comparing a soft proof to original art, match the white point in both viewing conditions. If viewing the artwork in a booth with 5000K lighting, then the monitor displaying the screen image should also be calibrated to a 5000K white point. Otherwise, the mismatch will invalidate any evaluations of color, because your eyes cannot chromatically adapt to both white points simultaneously.
NOTE: For more detail, please refer to ISO/DIS 12646:2008 (Graphic technology — displays for color proofing — characteristics and viewing conditions) and ISO 3664:2000 (Viewing conditions — graphic technology and photography). - When comparing a soft proof to a hard-copy proof, a white border of at least one inch must surround the soft proof.
- Do not compare individual colors in isolation, since they may need to be different colorimetric colors in order to produce the same color appearance within the context of the whole image.
- View the reproduction at an appropriate viewing distance. If it is to be printed on an 8½ x11-inch page and the original art is much larger, if viewed together they must not be side-by-side, but rather each should be assessed at their natural viewing distances.
For art reproduction, raw and DNG formats are not recommended as submission formats, since the images will need different rendering, depending on the final output, in order to maintain consistent color appearance. The only way to control this is by providing a rendered image tagged with an ICC profile.
imaging workflow
Image Capture. The only way to control digital captures for art reproduction is with professional equipment. Consumer-grade cameras and scanners introduce image processing intended to create preferred color for typical photography. This type of processing is counter-productive when the goal is appearance matching.
For two-dimensional art, first perform flat fielding to compensate for lens falloff and uneven lighting. For 3-dimensional art, flat fielding is necessary only while capturing the calibration target. Next, calibrate the camera's color. There are several solutions available for this. Depending on the art being photographed, some solutions may perform better than others, so try multiple solutions to find which work(s) best for different art media.
The most common reason for a camera calibration to fail is metamerism. Because cameras see color differently than people, different artists' materials (oil paint, watercolor, silver-gelatin photographs, chalk, etc.) can appear to have the same color yet photograph differently. The more widely the spectral nature of the materials photographed differ from the materials in the calibration target (such as a GretagMacbeth Digital ColorChecker SG), the more likely there will be color errors. Making a custom target from the same materials you are photographing can alleviate this problem, although doing so properly is difficult.
Scanning. Scanning transparencies is more straightforward than digital capture. Use one of the excellent, available software solutions to characterize (profile) your scanner. It is also very important to consider whether a transparency accurately represents the art. Transparencies have narrower limits in color fidelity when compared to digital captures and generally require more color-editing effort.
Printing. Characterize your printer by creating an ICC profile, and apply that profile in your printing workflow. Affordable consultants can help with this.
File Standards. Images extracted from the internet and video are unacceptable for art reproduction. Most images from these sources contain insufficient resolution or color gamut to produce quality reproductions, lack proper color management information and could have copyright problems.
Applying these best practices should produce digital files that meet the general specifications outlined above, although modifying existing files to meet these standards can be difficult. Such practices as resampling, color-space conversions (changing the color gamut), color mode conversions (between RGB and CMYK) and file format conversion (e.g., low-quality JPEG to TIFF) may cause more harm than good. Unless you have the experience to understand the consequences of each adjustment, leave an image as it is. The best workflow is one that conforms to these standards from the initial image capture.
file delivery
Outbound. When supplying images, it is also important to conform to the guidelines in this document. Ideally, provide a guide print along with a ReadMe file to instruct printers in correct color handling. As online delivery systems for press-ready files continue to proliferate, it will not always be possible or cost-effective to deliver guide prints. For this reason, printers who have adopted an ICC workflow should be favored.
Inbound. To receive images from outside sources, ask the provider for image files that conform to the guidelines in this document. Sample request language follows:
file request template
| Please provide digital files as follows: | |
| Resolution | 400 pixels per inch |
| Size | 12 inches long dimension |
| Bit-Depth | 8-bit |
| Color Space | Adobe RGB (1998) |
| File Format | TIFF or high-quality JPEG |
| ICC Profile | Embedded |
NOTES:
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Files submitted as above allow us to extract details and make moderate-size reproductions without up-sampling.
A more detailed discussion of the topics introduced here, including templates and instructions for printers, can be found at www.imagemuse.org.