How to use color management, Part 2


How to use color management in your camera

If you are capturing RAW images, then there is nothing you need to do. RAW images are simply a list of numerical measurements of brightness at each pixel on the sensor. These lists will be converted by your imaging processing software into colors at which time a color space will need to be chosen, but this happens in your computer, not in the camera. A RAW file does not have a color space, but the camera sensor can capture most colors seen in nature.

If you are capturing JPEG images, then the image processing does occur in the camera and a color space is assigned. Most DSLR cameras have a place in the menu to select a color space. Typically, the choices are sRGB or Adobe RGB. In general, Adobe RGB is the best choice because it is the larger color space. However, if you plan to publish directly to the internet and anticipate the image will mostly be viewed on sRGB devices, then sRGB might be a choice. However, as noted in Part 1, iPhones 6 and up use a color space similar to Adobe RGB.

How to use color management when processing images

When you process images on your computer, you need to define a color space. However, this is different for Adobe Lightroom than it is for Adobe Photoshop (the two programs I am familiar with). Adobe Lightroom automatically assigns its own proprietary color space which is very similar to ProPhoto RGB. It also uses 16-bit processing which is necessary for large color spaces. In Lightroom, you only need to choose a color space if you export the image into another file format such as JPEG or TIFF, or if you print the image (in which case you use an ICC profile, see below). Adobe Photoshop requires that you choose a color space on opening a RAW file, either from Lightroom or Adobe Camera RAW. The default is Adobe RGB. You can change this by going to Edit -> Color Settings. Whether to change the default color space, specifically to ProPhoto RGB, has been debated. I think there is a wider consensus that ProPhoto RGB is the best choice for serious photographers. The reason is that there are some natural and many man-made colors that are outside of the Adobe RGB color space. Although no current monitor can display these colors, some future monitor may be able to do so. In addition, high quality printers can print some colors that are not defined in the Adobe RGB color space, but are defined in ProPhoto RGB. For example, my old Epson R2880 printer uses the Epson K-1 inkset. The color spaces of Prophoto RGB, Adobe RGB, and the R2880 printer are shown on this illustration.

The R2880 printer (dashed yellow line) is able to print colors in the green and blue spectrum which are not defined in Adobe RGB, but are defined in ProPhoto RGB. (On the other hand, there are colors in the blue-violet range which I can see even on my sRGB monitor, but which my printer cannot print, an issue with some wildflowers.) The drawbacks to ProPhoto RGB are mainly related to the size of the color space. For nature photographers in particular, ProPhoto RGB defines many colors you will never see. It is also absolutely necessary to use 16-bit processing to have enough levels to cover this large space, which in turn leads to much larger files than 8-bit. However, with modern computers, processing speed and storage space are not usually an issue unless you take thousands of images. You may also need to be careful to convert the image to a smaller color space such as sRGB if you are going to display on a device which uses a smaller color space. Otherwise the colors will appear undersaturated. However, this is only a problem if the software for the display device does not automatically make the conversion, which many devices do. Overall, I think the benefits of ProPhoto RGB outweigh the drawbacks for serious photographers, All this being said, however, Adobe RGB will work well for most images, and is certainly sufficient for casual photographers. For Photoshop Elements users there are usually only two choices, which are to process for printing (Adobe RGB) or for the internet (sRGB).

How to use color management on your computer monitor

Most image display programs automatically convert to your monitor’s color space. Therefore, you don’t have to do anything to your image to display properly. Usually the rendering intent for this is Relative Colorimetric. You can change this under Color Settings in Photoshop, but I wouldn’t. However, the most important thing you need to do is calibrate your monitor. As others have said, this is not optional. Most consumer monitors are set very bright out of the box, and the color may not be accurate. To calibrate your monitor requires purchasing a spectrophotometer and associated software. Some common brands include the X-rite Colormunki or Datacolor Spyder series. It is not necessary to buy the most expensive model. It is more important that you do it. Even a streamlined calibrator will help. The software displays defined colors on your monitor which are read by the spectrophotometer. The software then creates a file which adjusts your monitor display to be sure the colors are accurate and also to adjust monitor brightness. Photos shared between photographers using calibrated monitors should look pretty similar from one monitor to the next. If you share them with family and friends whose monitors are not calibrated, who knows what they will look like?

How to use color management for printing

What to do here depends on whether you print your own images or send them out to be printed. If you send them out, the printing company will handle the color management, but you should ask them what color space they want the file to be in. As discussed above, you need to specify a color space when you export a file from Adobe Lightroom. Assign the profile to the one the printing company requests. In Adobe Photoshop you can change the color space from your default using Edit -> Convert to Profile. You choose the new profile and rendering intent before saving the file.

If you print your own images then you will need an ICC profile (for International Color Consortium) to tell the printer how to handle the colors. The subject of how to make a print is beyond the scope of this discussion, which is limited to the subject of color management. However, you need to know that for every paper and ink combination, a different adjustment needs to be made to the printer output. These are encoded in the ICC profile. Professional photographers, particularly if they are using unique papers, may make their own ICC profiles using a special spectrophotometer and software for reading a test print. There are also commercial services which will do this for you if you send them the appropriate test print (which requires special software to generate). Most of us use the ICC profiles provided by the paper manufacturer. For most commonly used printer papers, the paper manufacturer will provide an ICC profile specific to your printer which you can download and install. The profile was made on a presumably identical printer to yours, and presumably will provide proper color adjustment. Depending on which software you use to make the print, you need to specify that the software will manage the colors rather than the printer. You also need to specify which ICC profile you are using and choose a rendering intent. You may have to make some test prints to see which rendering intent works best. There is also a technique called soft-proofing which does work to choose the rendering intent, but is beyond the scope of this review. For an in-depth discussion about how to make a print see Jeff Schewe’s book, The Digital Print.

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