Fine Art Reproduction Configuration Guide

Transcription

1 Prepared for Hasselblad by Scott Geffert Spring 2012 Version 1.0

2 The steps outlined in this guide have proven to be a reliable method for calibrating Hasselblad cameras (using Phocus version software or later) to meet or exceed emerging digital imaging protocols especially critical for artwork reproduction. The European Metamorfoze Digital Preservation Imaging Guidelines and US Federal Agency Digital Guidelines Initiative (FADGI) are two methods of objective image quality verification based upon known targets and predefined tolerances. The guidelines provide an important foundation for imaging quality assurance and quality control. ISO (International Standards Organization) efforts are currently underway to unify metrics, related methods, and tools used to specify and measure image quality capability of systems for recording and evaluation of cultural heritage materials for archival purposes. What does this mean? Users worldwide can begin to take advantage of more consistent digital imaging methods less prone to subjectivity. With clearly established universal rules of the road digitization vendors and manufacturers can be held to specific performance criteria very similar to current offset printing specifications such as Fogra or GRAYCoL 7 (G7). An objective verified digital capture of an artwork insures a predictable reproduction using methods that can be re-created at any site worldwide. While the capture protocols cover all aspects of image quality, this guide will focus on meeting the Metamorfoze tolerances for color and tone. As the protocols share many of the same ISO aims, passing the Metamorfoze tolerances for color and tone will automatically satisfy the FADGI color and tone reproduction requirements. The calibration process outlined in this document requires the following third party tools: The X Rite DCSG Color Chart* (Digital Color Checker Semi Gloss) and BasICColor Input software*. While ANY ICC compatible camera profiling tools can be used, the BasICColor profiling software has proven to deliver extremely accurate profiles helping users easily meet or exceed current protocols. Regardless of profiling tools, or brand of camera (or scanner) the most important step is the validation of the tone and color response of the imaging camera system. There are several ways to validate the results of your profiled camera system. The Metamorfoze protocol offers easy to use manual tables for exposure and tonal response values. To properly validate both your color and tone performance there are currently two tools available: the Image Engineering iq-analyzer 5 Color Module* or the ISA ColorGuage SG Analyzer software*. These tools are designed to analyze the color results of your system as part of your ongoing process control / standards compliance protocol. ImagingEtc also offers remote imaging performance verification services *Visit for more detailed information on remote imaging performance validation or to purchase third-party tools.! 2

3 Capturing the DCSG chart for profiling 1) Set up the camera to fill the frame with the DCSG color chart (if you are capturing larger artworks it is OK to allow the chart to be smaller as long as it is placed in the center of the image illumination area). For best results two light sources should be used in a classic copy work configuration i.e. equal distance, equal power, positioned at an angle of 30-to no more than 45 degrees from the plane of the artwork to avoid glare. If using large light sources pay particular attention to minimize glare.! 3

4 2) In the Adjust Tab under Adjustments Browser select the Standard preset and click Load. This will insure that no custom adjustments are being applied during the chart capture process. 3) In the Capture tab under Reproduction select Hasselblad RGB and check Reproduction Mode. Also make sure the Reproduction panel is checked. 4) In the Export tab under Output Preview create a new export preset with the following options: File Format: 16bit Tiff, Dimensions: Full Size, and Source as the Output Profile. Name the preset For Calibration. This will essentially disable color management. (See screen shot on the next page)! 4

5 6) Create an initial exposure of the DCSG chart and neutralize the camera by clicking on patch G5.The RGB readouts should be equal, or in the LAB readouts, the a: and b: values should be 0,0. Output RGB Values: R=G=B L*A*B* Values: a=0 / b=0! 5

6 7) Adjust the illumination until you reach a value of 97L for patch E5 of the DCSG chart using the LAB readouts. Avoid using Aperture, ISO speed or exposure slider adjustments; it is best to adjust your lights to achieve the exact exposure value. You may find that strobe pack controls will not be precise enough to reach the specific value, so simply move the light sources distance to fine-tune the exposure. 8) Export the image making sure to use the For Calibration preset. Note: Cropping the chart before exporting will make profile creation easier! 6

7 Creating a color profile using BasICColor Input 1) Launch BasICColor Input, load the DCSG color chart image by clicking the Select button next to Image, then Locate the Digital Color Checker SG Reference data (spectral reference data) as pictured below 2) Crop the chart, and drag the upper left and lower right corners to align the corners until all patches are clear. A small square in any patch indicates that the sample is not aligned well. You can enlarge the window and zoom into the image if needed! 7

8 3) Name the profile in a way that will make it easy to identify. Avoid spaces and special symbols 4) Select D50 from the viewing condition (listed under cie Illuminants) and leave the boxes for camera gray and absolute white unchecked 5) Create the profile. The ICC profile will automatically be saved to your Colorsync User folder. Note: Under OS X Lion the user library is hidden by default (to reveal the User>Library>ColorSync folder, select the Go Menu in the Finder and press the Option key) Configuring Phocus for Profiled Capture 1) Relaunch Phocus, and set your Export settings to your preferred working space (i.e. ecirgbv2, ProPhotoRGB, AdobeRGB). ecirgbv2 is available for download at and is the preferred working color space due to it s L* based tonal gradation. 2) In the Reproduction tab in the Capture pane, select your custom profile from the list (instead of Hasselblad RGB). Make sure Reproduction mode is selected and that the check box for the reproduction tab is checked.! 8

9 3) Make a new exposure and check your white exposure value (after profiling it is common for the exposure to shift slightly) Adjust your lights to get the white exposure for patch E5 back to 97L. It is easier to move the lights a few inches than to use the flash power because the flash power will usually be too coarse for this adjustment. 4) Using the Metamorfoze exposure tolerance tables for your current working space, check that the captured DCSG chart values are within the tolerances listed for each gray patch. You can use the RGB or L*A*B* readouts and tables interchangeably. Note: you may find that certain patches may be near the high or low limits of the tolerances, this is acceptable as long as values do not fall outside of the upper and lower limits for each step. You can also use the L*A*B* readouts and tables. DCSG chart image files with RGB gray scale tolerances are available for download at 5) If certain values are found to be out of tolerance and the white exposure is correct you can adjust the Tone Curve to compensate for your particular lighting situation. This tone curve will be used together with this specific color profile for subsequent captures. Most users will save the tone curve and profile as part of a user preset.! 9

10 Condensed Version (once you are familiar with the process) 1) Disable Color Management:! Output profile set to SOURCE! Input set to HASSELBLAD RGB! Reproduction Mode ON! Vignetting ON,100% or create a custom white reference (see appendix 2) 2) Capture the chart, neutralize on patch G5 and expose to 97L on patch E5 using the linear curve 3) Export the chart, quit Phocus 4) Open BasICColor Input, open the chart image and DCSG reference data. Crop and create a custom profile using D50 illuminant. 5) Relaunch Phocus, select the new profile, set your export space to your current working color space 6) Re-Check the E5 (white) patch and adjust lights if necessary to reach 97L, then verify the chart tone scale against the Metamorfoze tolerance table for L* or your current working space RGB tolerances 7) Export the file, (crop to the chart) 8) Verify the color and tone using the Image Engineering Color Module or ISA Color Gauge SG software or have the file evaluated independently (imagingetc offers image validation reports as a service but suggests it is always best to maintain quality control and color management as an ongoing in-house function). Note: Fine Art Reproduction Configuration Guide The tolerances for color are slightly different between the Metamorfoze and FADGI protocols. The Metamorfoze method relies upon the CIE 1976 color difference formula and the FADGI relies upon the CIE 2000 color difference formula. The CIE 2000 is generally more forgiving as it is weighted to accept larger errors in color regions where our eyes are less sensitive. The CIE 1976 simply measures raw color differences with no specific weighting. This helps clarify why a pass result of the Metamorfoze will in most cases will automatically pass the FADGI tolerances. For Metamorfoze: Average DeltaE (CIE 1976) should be less than 4 Maximum DeltaE (CIE 1976) should be less than 10 For FADGI: Average DeltaE (CIE 2000) should be less than 3 Maximum DeltaE (CIE 2000) should be less than 6! 10

11 For 2D work Capturing Tips: Reproduction mode needs to be ON with your custom camera profile selected. the Tone Curve should be Linear (default) unless your particular configuration requires tone curve adjustment to reach the Metamorfoze tonal tolerances. For best results, before shooting 2D work, try to verify that your pool of illumination is even (within 3 Luminance values corner to corner). If the illumination is not even, check your Hasselblad Vignetting settings. Generally, the Vignetting setting of 100% in an even pool of light will be perfectly fine. If you cannot achieve this with lighting alone, you can create a custom scene reference with the help of the white calibration card. Note: if you create and use a custom scene reference, Vignetting should be OFF! 11

12 For 2D work (continued) Place your DCSG target in the center of the illumination area (before placing the artwork) and check the exposure is correct (white patch G5 = 97 L*). If you are concerned about glare due to very soft lighting situations, the black patches along the edges of the DCSG chart are a good indicator. If the black L* values are very different (more than 3 L*) you should adjust your lighting. You can also use the DCSG chart to manually check that the gray patch values match the Metamorfoze tolerances. Note: when capturing 2D artworks make sure that exposure, contrast, clarity and color settings are all set to default.! 12

13 For 3D work Turn Reproduction mode OFF Custom profile ON Turn OFF any custom scene calibrations Turn Vignetting ON -100% Under the Exposure panel set the following: Contrast 5, Brightness 5, Clarity 5. All other settings remain at 0 Note: The 3D settings listed above are simply a suggested baseline that has worked well with Phocus across a number of museum photographers and object types. There are currently no international standards or protocols for photographing 3D objects that can be applied across multiple camera brands. All current measured capture protocols and chart-based validation methods are limited to two-dimensional artworks.! 13

14 Optional Custom Scene Calibration Profiling Method: Creating a custom scene calibration prior to profiling will generally result in a more refined profile with even greater accuracy, yet many people will meet or exceed the protocols without incorporating this step. This step is helpful for more advanced users wishing to achieve even tighter tolerances. A custom scene calibration can help mitigate problems with light falloff, color temperature differences between light sources etc, but it is important to note that the best way to resolve these issues is via addressing them at the source. Turn Vignetting OFF and disable any custom Scene Calibrations. 1) Take an initial capture of the DCSG chart and neutralize the camera by clicking on patch G5. The RGB readouts should be equal or in the LAB readouts, the a: and b: values should be 0,0. Try to use an aperture that would be typical for your work. 2) Adjust the exposure (ideally using the illumination power level) until you reach a value of 97L for patch E5 of the DCSG chart in the LAB readouts..you will find that the strobe packs (even with 1/10 stop adjustment) may not be precise enough to hit the specific value, so simply adjust the light source distance to fine tune the exposure.! 14

15 3) Place a white scene calibration board (this is a smooth spectrally neutral material with an L* value of 70 to 97) in the scene on top of the DCSG color chart and defocus the camera slightly. The material must be clean and must fill the frame completely. Capture the chart. 4) Check the consistency of the lightness of the chart from corner to corner as well as the center. Make note of any variations in color or density. Typically the values are darker on the edges of the frame. If your light is even, the corner to corner values should be within 3 L* values! 15

16 5) In the Scene Calibration tab click Create and name the setting in a way that describes the configuration. Click Remove cast and Equalize Intensity to enable the settings. You should now have a perfectly even scene. You can check this by measuring digital values across the capture area. You will notice the values are now equal. 6) Remove the white board, refocus and capture the DCSG chart, neutralize on patch E5 and re-check that the white exposure is exactly 97L (very important!) 7) Export the DCSG chart capture and Quit Phocus 8) Create a custom profile (see page 7: Creating a Custom Profile using BasICColor ) 9) Install the custom profile (see page 8: Configuring Phocus for Profiled Capture ) Note: If the camera distance, lens, aperture and light position are exactly the same as when you created the custom scene reference you can use the custom scene reference for capturing your 2D artwork. If ANY of these variables are altered, a custom scene reference could easily work against you. In most cases when using Hasselblad bodies and lenses, the Vignetting set to 100% and careful attention to lighting will give best results. Never combine a Custom Scene Reference with the Vignetting control under Lens Corrections however, you can use the Chromatic Aberration and Distortion corrections at any time.! 16

17 Image Validation: There are multiple methods of image validation. Methods can be combined or used individually to assess and monitor your imaging program. 1) Table / Readout Based: Fine Art Reproduction Configuration Guide!Published Tolerance Tables are part of both the Metmamorfoze and FADGI guidelines. While they differ slightly, the goals are the same: to give users a pass or fail set of tolerances around the actual chart reference values. In the case of the Metamorfoze protocols, tables are provided for every form of grayscale target and every common working color space including easy to understand L* values. To use these tables, read the image values with your eyedropper and compare them to the published tolerances for each grayscale step in your desired destination color space. As stated earlier, the tolerances are only useful for exposure and tone values and do not describe color accuracy. This chart lists the Metamorfoze DCSG tolerances for the ecirgbv2 Color Space ONLY (For other working space tolerance tables and tools visit )! 17

18 2) Software Validation of Color and Tonal Response:!Color validation tools compare published chart reference data to the actual data in your chart images. Each tool presents color differences using various graphing schemes and numeric reports. The Image Engineering IQA software helps visualize imaging performance via graphic feedback: Red values (over 10) represent failures, and Green values are near-perfect matches. The ISA software (PC only) offers numerous graphing and reporting options. These tools are generally cross-compatible in that they refer to the same reference data and can be configured to display different tolerance models. *Note: ImagingEtc offers remote image validation services (see the included order form) Image Engineering IQ-Analyzer_Color!! ISA Color Gauge Analyzer 3) Artwork Validation!The most fascinating type of image color and tone verification is to measure the actual artwork colors using a spectrophotometer (Like the Minolta FD-7 or X Rite Eye One Pro) and compare the resulting values with your digital capture. To do this you carefully sample the artwork and write down the L*A*B* values, then using the Adobe Photoshop Color Picker, enter the (rounded) L*A*B* values and add the color samples into a layer on top of your image in the exact measurement locations.! 18

19 Sample of Artwork Validation: Fine Art Reproduction Configuration Guide Sample Measurement Locations To calculate DeltaE differences you can download the handy ColorDiff iphone App or visit the web site of Bruce Lindbloom ( to use his Color Difference Calculators. Simply enter the L*A*B* values from the artwork and the L*A*B* values from your file. The software will return the calculated DeltaE difference values When spectrophotometer measurements and validated captured color values agree, you can rest assured that your capture is as faithful as today s technology and color science will allow. Will the validation process guarantee that every print will match the artwork? Not always. The goal of objective capture method is to digitize artworks faithfully for longterm preservation. The accurate image file may require media-specific optimization primarily to compensate for the wide range of unique device and media color capabilities. For example a very colorful painting may appear dull on matte ink jet media or a CMYK offset press proof due to differences in dynamic range and color gamut.! 19

20 A note from the Author: I have tried to give a complete summary of the specific steps and tools required to achieve high quality results with this particular camera system using minimal third-party tools. As an advocate of imaging standards I envision a day when all camera systems will be required by customer mandate to incorporate direct support for calibration, verification and certain universal UI elements. Until then, the third-party tools listed in this guide are necessary to reach and maintain this level of precision. My company ImagingEtc was created ( with the goal of offering the specialized tools and support required to help people adopt best practices in imaging. The tools that you will find on the web site have been carefully selected from vendors around the world based strictly on performance, and are not typically found at your local photo or computer catalog stores. There are numerous places to purchase computers, cameras, and other commodities, but few cater to the unique needs of the fine art and cultural heritage communities. A special Resources section of the web site is dedicated to offering the community free downloadable guides, technical targets, exposure tables, color profiles and other useful items. Please visit this area and feel free share it with others online. For For people new to standardized capture protocols ImagingEtc offers low cost remote image validation services using the latest image analysis tools to give users hard copy reports regarding imaging performance. While adopting standardized methods for imaging requires some up front investment, the long term benefit is an increase in productivity and predictable quality over time. When coupled with validation software you can literally verify each step of your colormanaged workflow from capture and display to the ultimate output. You can even extend your quality control methods to your clients and outside vendors. It s a great feeling when you finally have control over your entire imaging workflow. Enjoy! Scott Geffert info@imagingetc.com Scan to your smartphone This Document was printed on a Konica Minolta Biz Hub PRESS C8000 Courtesy of: Russell Doucette, Business Development Manager Konica Minolta Sensing Americas, Inc. 101 Williams Drive Ramsey, NJ Office: Mobile: rdoucette@se.konicaminolta.us! 20