Color Matching and Quality Control by Calibrated Digital Photography
Wednesday, February 9, 2011 at 9:00 AM (EST)
Custom color‐-matching of repair systems and coatings for use in historic masonry restoration work has generally involved removal of existing materials and shipment to the repair system manufacturer's lab for analysis and matching.
Challenges within this approach have included:
1. Collection of samples can cause further damage to the structure.
2. Collection of an accurate, representative range of color samples can be difficult.
3. In the lab, spectral analysis using spectrophotometers and color-matching software is inaccurate for materials that are multi-colored, deeply textured, curved or highly variable.
The maturing of digital camera technology provides the opportunity to perform colorimetric measurement with relatively inexpensive, readily available equipment. High quality images from digital single lens reflex cameras (DSLRS) can now be obtained in a color-managed environment. For each area and lighting condition, it is possible to calibrate the color response of the camera. When images are captured in RAW mode, color calibration software can "develop" the information from the sensor into an image that is color accurate within certain tolerances. Adobe Photoshop can then be used to obtain color information in the international standard CIE L* a* b* format for any size area of the photograph. Each color can then be identified by three numbers. This data can be utilized by color-matching software systems at the manufacturer's lab or for analysis and comparison of colors by the user.
This hands-on workshop will allow participants to learn how to capture and process high-quality calibrated digital images in RAW format that can be used as tools to assist in color matching and color quality control.
The first part of the workshop will concentrate on how to take calibrated photos. These photographs can be sent directly to Edison Coatings where the lab staff will "develop" and process the photos and then derive quantitative L* a* b* numbers needed for computer-controlled color matches. This section of the course will concentrate on cameras and photographic techniques and will include everything necessary to take a photo for calibration. Topics will include: what is a "raw" photo, how to include reference standards in the photo, pre-set white balance, lighting, getting the exposure correct, avoiding blown highlights and channels, learning to love histograms, using blinkies, using manual settings, lenses, and avoiding common problems .
In the second part of the course, participants will learn how to develop and calibrate the photos themselves using calibration software and Adobe Photoshop and Adobe Camera Raw. Participants will learn how to measure the color in selected areas of the photos using Photoshop, giving the user greater control over which colors are selected for matching.The color data can also be used to evaluate color differences on the building to guide the decisions about how many colors will be needed to match the building. This information can then be sent to the factory for direct input into the computer color matching system. In addition, data can also be developed to evaluate color differences between sample materials and the building surfaces, in order to refine the computer-guided matches or to provide a quantitative basis for quality control. Participants will also learn how to prepare color swatches of the measured colors and to place them on the photo for easily analysis and comparison.
Techniques will be demonstrated using readily-available and moderately-priced cameras, equipment and software on a class-sharing basis. If participants have any of the following equipment and software, they are encouraged to bring it and use it during the workshop:
- A notebook computer, running Photoshop and Adobe Camera Raw (included with the more recent versions of Photoshop), and spreadsheet program that will read Excel files
- A digital single lens reflex camera (DSLR). Nikon cameras will be demonstrated and shared during the workshop. We are most familiar with Nikon equipment but any brand DSLR can be used.
Thumb drives will be given to each participant to use for transporting data during the workshop. Drives will be preloaded with useful information and articles, sample photos, and spreadsheets for calculating L* a* b* data.
No previous experience is required. Background information on color practices and photographic techniques will be provided during the workshop. Some experience with photography is helpful but not required.
The Color Workshop is targeted towards individuals and organizations including facility managers, architects, conservators, contractors, project managers, and engineers that are involved with masonry color matching problems. The enrollment in the course will be limited to 12 individuals, to allow full participation by all attendees.
Location and Date:
The Color Workshop will be held at the Edison Coatings Training Center, Plainville, CT
February 9, 2011 from 9:00am to 3:30pm. A box lunch will be included as part of the fee.
When & Where
Edison Coatings, Inc.
For 34 years, Edison Coatings, Inc. has been developing and producing custom repair mortars, repointing mortars, coatings and adhesives for historic masonry, stone and concrete buildings and structures. The Company has a particular focus in Terra Cotta Restoration and Historic Mortar replication.