March 28, 2007
The Camera Calibration panel in Lightroom can be used (with a little help from Photoshop) to calibrate your digital captures to get the most accurate color. But that’s not all. If you play around with the sliders you will find that you can also use the Camera Calibration panel to do the very opposite of what it is meant for and create some unusual coloring effects.
The camera raw conversions in Lightroom are the result of many years painstaking work, in which Thomas Knoll (who with his brother John created the original Photoshop program) evaluated the color response of lots of different cameras. Basically, for each camera raw format that is supported, Thomas made two profiles which measure the camera sensor’s color response under controlled daylight and tungsten lighting conditions. Using this data, it has been possible to extrapolate what the color response will be for all white balance lighting conditions that fall between these two setups and beyond.
Now, there are around 150 different cameras supported by Adobe Camera Raw and Lightroom, and in some instances several camera samples were tested to obtain a representative average set of measurements. And other times only one camera model was actually used. But in all cases it is clear that the measurements made by Thomas can only ever be as good as the camera or cameras from which the measurements were made (and how representative these were of other cameras of the same make). Because you know, the sensors in some cameras can vary a lot in color response from camera to camera. This variance means that although a raw file from the camera you are shooting with may be supported by Lightroom, there is no absolute guarantee it will be exactly similar in color response to the raw files from the cameras Thomas evaluated. This is where the Camera Calibration panel comes in, because the Camera Calibration panel sliders can be used to make fine-tuned adjustments to the camera’s color response.
Creating a custom calibration via Photoshop
If you have Photoshop CS or later, there is a way to automatically create a custom calibration for your camera that involves the use of Thomas Fors ACR Calibrator script. This script will work for Mac or PC and can be downloaded from: http://fors.net/chromoholics/. Install the script in the Photoshop application/Presets/Scripts folder, then restart Photoshop and follow the instructions on the page opposite. The script will open a new ACR Calibrator Status Window (see Figure 4) and run through a series of steps, in which the raw image containing the color checker chart will be opened many times using different settings and measure the results. This process can take a very long time to complete, which is why it is important to keep the bit depth at 8-bits per channel and the image size small. It will also help if you hide all the palettes first before you run the script. Note that apart from setting the bit-depth to 8-bit and the pixel dimensions to the smallest output size, there are no other settings you need concern yourself with. It does not matter if the auto settings are on in Photoshop or not and it does not matter which RGB output color space is selected.
Figure 2. To use the ACR Calibrator script, you will need to photograph a Gretag Macbeth ColorChecker chart and open the raw file via the Adobe Camera Raw dialog in Photoshop. Use the white balance tool to measure the circled patch (next to the white patch). Next, crop the image tightly around the ColorChecker chart, set the crop size to the smallest resolution possible and set the bit depth to 8-bits per channel. Now click Open to open the image in Photoshop.
Figure 3. With the image open in Photoshop, select the pen tool with the Paths mode option selected in the Tool Options bar. Click with the pen tool on the brown patch followed by the white patch, the black patch and lastly the blue-green patch. Now go to the File ➯ Scripts menu and select the ACR Calibrator script. The script will automatically open the raw file many times over and gradually build a Calibrator status report in a new Photoshop document.
Figure 4. Here is the ACR Calibrator Status Window after the script has run its full course. I have highlighted the calibration settings in yellow. You need to note these figures down, enter these in the Calibration panel in Lightroom and save these as a custom calibration setting for your camera. You may also want to make a note of the Color temperature white balance and Tint settings and save these too as part of your custom calibration setting. That’s it, you are all done and the calibration setting you have created should be good for a variety of color temperature settings.
Camera Calibration panel color effects
But as well as using the Camera Calibration panel to get accurate color, you can also use the Camera Calibration panel to produce different color effects.
Figure 5. This shows a standard version of an image with zeroed Camera Calibration panel settings.
Figure 6. This is a vivid color setting that was created using the following Camera Calibration settings:
Red Primary Hue: 0
Red Primary Saturation: +85
Green Primary Hue: +85
Green Primary Saturation: +85
Blue Primary Hue: 0
Blue Primary Saturation: +50
Figure 7. To create this magenta sky effect, I used the following Camera Calibration settings:
Red Primary Hue: -40
Red Primary Saturation: -40
Green Primary Hue: +30
Green Primary Saturation: +30
Blue Primary Hue: +80
Blue Primary Saturation: -100
But in addition, I adjusted theHSL panel luminance, lightening the yellows and greens to +35 and darkening blue to -35 and darkening purple to -14.
Figure 8. To create this color infrared effect, I used the Camera Calibration settings shown here.
Red Primary Hue: +70
Red Primary Saturation: -30
Green Primary Hue: -45
Green Primary Saturation: +20
Blue Primary Hue: -100
Blue Primary Saturation: -40
In addition to this I set the Shadows in the Split toning panel to Hue 180 and Saturation 25. Bear in mind that with all the settings figures shown here, these are just guidelines. You will find that individual images may suit slightly different variations.
Figure 9. You can of course save the Camera calibration settings for settings such as the infrared color effect and apply them to other images. But it doesn’t always work so great on portraits.
This article is an excerpt from The Adobe Photoshop Lightroom Book by Martin Evening, which is shipping now. In special arrangement with Martin and his publisher, PhotoshopNews has a free PDF download of Chapter 1. (click HERE to download-4.6MB PDF)
The Adobe Photoshop Lightroom Book describes Lightroom’s features in detail and with photographers in mind. Photographers who routinely work with raw (and even jpg & tiff) images will find Lightroom–and The Adobe Photoshop Lightroom Book–an indispensable tool in their digital darkroom.
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The Adobe Photoshop Lightroom Book
by Martin Evening
Publisher: Adobe Press
ISBN-10: 0-321-38543-8; ISBN-13: 978-0-321-38543-7
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