What is camera calibration

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Cameras describe colors as a mixture of red, green and blue (RGB). The amount of each color is described by a number. The number combination (0,0,255) equals a dark, saturated blue color and (128,128,128) represents middle gray. Just like with people, each apparatus registers a color just a little bit different than another apparatus. One camera will describe a specific color as (100, 240, 100), whereas another camera will describe exactly the same color as (0, 237, 40).
How is a printer or LCD screen to know which color to show you, if two different cameras produce such different numbers for exactly the same color?

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The solution for this problem is called color management. By calibrating all equipment you are using in your workflow, from camera to printer, you can assure colors remain unchanged. Many photographers are used to calibrating their LCD screens, but are unfamiliar with camera calibration. Adobe offers a helping hand, by giving you Adobe DNG Profile Editor for free. You can use this free downloadable software to calibrate your own camera. But you do need an official color checker card. The question remains: Is it worthwhile to calibrate your own camera?

Camera color management

In order to standardize color reproduction, a color management system had been designed by the International Colour Consortium (ICC). This system translates apparatus specific colors from one piece of equipment (computer) to another piece of equipment (LCD screen or printer). RGB numbers change from one apparatus to another in such a way, that the color remains exactly the same. Thanks to color management a calibrated printer can reproduce the colors you see on a calibrated screen in the best possible way. Color management of LCD screens, colormanagement of printers are generally accepted by both professional and advanced amateur photographers.
But the calibration of a camera is much less common. Most photographers use - often without even knowing - the standard Adobe color profiles for their camera underneath the hood of Photoshop or Lightroom. For every new camera on the market, Adobe has to produce and distribute camera ICC profiles (at two different color temperatures) first, before you can open and edit RAW files of that camera in Photoshop or Lightroom. This is one of the reasons why Adobe issues so many updates for Lightroom and Photoshop's RAW converter.

A camera ICC profile is generated on the basis of a picture of a color chart with well known color patches. The colors of the official color chart are compared with the colors in a picture of the color chart, made with your camera. The color a camera registers, depends not only on the color of the subject, but on the light source just as well. What we see is the combination of the color af the subject and the color characteristics of the light source. Candle light  has completely different color spectrum than shadowlight on a gray day. The same white shirt will appear light orange in candle light, but light blue in the shadow. These differnt color behaviours are describes with the Colr temperature, in degrees Kelvin Kelvin (K). Most cameras are able to register colors correctly between approx. 2.500 K (night), through 6.500 K (day light) up to 9.000 K (old fashoioned TV screen). Indeed you should make a camera calibration ICC profile for each color. But in practice most people are happy using two camera color profiles only: Adobe uses: 2850 K and 6.500K for Photoshop and Lightroom. These programs recognize in a RAW file which camera has been used and automatically apply ( acombination of) the 2 standard Adobe camera specific color profiles.

More about Camera calibration:

 

 

Free download for camera calibration!

You can download Adobe DNG Profile Editor for free. This stand-alone program is easy to install. You don't need Photoshop or Lightroom at your computer. But what you do need, is an X-rite Munsell color chart. You must make a picture of this color chart with your camera and save this file as a DNG file. You might wish to download Adobe's free DNG converters. Within a minute after opening the DNG file in Adobe's DNG profile editor, you will have your custom made camera calibration profile, which you can export directly to Photoshop or Lightroom, if you wish. The next time you open the Adobe Raw converter or Lightroom, you will find your custom made camera calibration profile, under the tab "Camera Calibration". Now you have the choice between Adobe's color profile and your own custom camera ICC profile. In many cases color differences between Adobe's color profile and your custom profile will be hard to see. Look for strong saturated colors or make a camera color profile in artificial light (tungsten) if you're hoping for large color differences .

Under normal daylight ( 5500 - 6500 K) most cameras will be able to reproduce colors very good (see our camera reviews if you don't believe it). But in mixed light situations (daylight and artificial light at the same time) or with scenes containing very saturated colors, it might still be useful to calibrate your camera for the best results. Sometimes the color rendition of one specific color (often saturated red or blue) deviates so much, the color difference between camera and actual color becomes noticeable. White balance correction doesn't help in such cases: adjusting the white balance for this specific color would ruin the white balance for all other colors. In such situations only camera calibration helps.

The effect of camera calibration in practice

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Calibrating a camera will not be necessary for most amateur photographers. In most cases the difference in color rendition of a calibrated camera and the uncalibrated camera will be visible, but subtle. To the left a kingfisher, as shown in Lightroom when you apply the standard Adobe color profile. The white balance is OK, but the belly of the kingfisher inclines a bit to much towards a brownish red. Applying a camera color profile, made using the Adobe DNG Profile Editor, this camera specific color cast in the oranges can be eliminated. To the right the bright orange belly of the kingfisher is rendered more naturally, thanks to camera calibration. A larger color difference between in front of and after camera calibration can be seen in How do I calibrate a camera?

 

 

Ivo Freriks
Author: Ivo Freriks
With Camera Review Stuff I hope to make a modest contribution to the pleasure that you get from photography. By testing cameras and lenses in the same way, evluating the results and weighing up the pros and cons, I hope to help you find the right camera or lens.

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