Basic Color Management
Have you noticed that your photos sometimes don’t match the image you see on your computer screen? There can be plenty of reasons why, but most are due to improper Color Management. Essentially, one or more of the settings in your color work flow is incorrect. Often, these issues can be traced to the lack of proper monitor calibration, including White-point, Gamma and/or an incorrect setting of the working Color-Space the files are viewed and corrected within.
White-point is actually the neutral color balance of the monitor screen measured in degrees Kelvin, (see Tim’s article about Color Temperature for more information) and can vary widely from device to device. The most reliable calibration will be achieved by using a plug-in device that measures the output of your computer screen. The probe is packaged with software that will take you through a step by step procedure to accurately set your monitor to the correct gamma and white-point. The software will also create a monitor profile that will minimize variations in visual output for your specific monitor. These products are available in a variety of styles, features and price ranges. If you plan to do any color correction to your digital files , it is an essential tool to have. You will need to verify and re-calibrate your monitor every few weeks or months, depending on use.
Gamma refers to a specific value of brightness and contrast. One of the key differences between Mac’s and Windows PC’s is the Default Gamma used on each platform. Mac’s generally use a gamma setting of 1.8, and Window’s use a setting of 2.2 which is the default gamma defined within the sRGB Color-space. In addition, most monitors are only capable of accurately representing colors in sRGB. You will want to make sure that the default working color space in Photoshop or raw file processor is also set to sRGB. Our Noritsu Pro 32 Digital imaging equipment is setup to print using sRGB so make sure to prepare your images accordingly.
Photographers that will be publishing their images in magazines or through offset printing will probably want to stay in the Adobe 1998 RGB color-space since this generally works better when CMYK conversion will be required for offset printing. Keep in mind that to accurately view and correct digital images in this space you will need to upgrade your monitor to a device that is capable of displaying the extended dynamic color range. We use Adobe 1998 when capturing images with our multi-pass scanning and when printing on our CANON PRO 4000 large format inkjet printer to make Studio Giclee’s. Although files shot in Adobe 1998 can be converted to sRGB, this will only add time to file preparation with no direct quality benefit when printing to photo output devices like our Noritsu QSS 3202 printer. Mismatches of these two color spaces can produce unintended and inferior results, so be sure to submit files in the appropriate color-space for the desired output type. When setting the defaults, we have found that using “Perceptual” as the rendering intent usually produces the most pleasing results.
Finally, make sure that your correcting monitor is located in a stable viewing environment where the ambient lighting will always be about the same. Although new ones are all but impossible to obtain these days, most CRT displays generally used to offer better overall color accuracy than all but the priciest LCD flat panels. On the down side, CRT monitors would dim and fade with extended use and as they aged, they would eventually not have sufficient brightness range to properly calibrate.
Whenever possible, you should avoid laptop displays for critical color correction since many of these screens are often too “cold” and without the necessary controls to offer a reliable color and/or density calibration. Using an incorrectly calibrated screen can lead to files which are improperly corrected and will produce inferior prints.
For laptop/notebook screens, the notable exception would be those premium priced systems that utilize Retina or O.L.E.D. displays. These systems, when properly calibrated can be quite accurate, as long as they are consistently used with AC power in a stable viewing environment.