From Chapter Two:
Color space is a term that drives many people up the wall, and sometimes that includes me. I think that this is the case, at least in part, because this phrase is used by so many people who are using different tools and are trying to achieve different goals.
As a photographer and artist, I tend to think of color space as I might imagine a painter’s color palette. In a sense, a color space describes what is contained in that palette: how many individual colors there are, how many variations exist of each color, how dark or light they are, where they are located in the palette, and so on. Some palettes are bigger and more varied than others, and some palettes have dif-ferent colors–and the same is true of different color spaces.
Just as with an artist’s palette, most color space models that have been created represent only a portion of what we can actually see. For example, the human eye and brain can see millions of colors and tones. The color space that most closely represents this is called LAB color space.
Among other things, different color spaces can be collected into libraries. Each color space has its strengths and weaknesses and so is used in turn for a specific purpose. The most commonly used color space on the Internet, and in many displays, is sRGB, which can only provide 256 tones in each channel of red, green, and blue. It works just fine on the computer displays most people see every day.
The sRGB color space is limited; it can’t handle many of the colors that can be printed using an ordinary four-color printing press or by many digital inkjet printers. These four-color printing machines commonly use what is called CMYK (Cyan, Magenta, Yellow, Black) inks, which are combined into a range of colors; digital inkjet printers intended for printing photographs typically have at least six colors of ink, which can be combined in printing an even broader range of colors than CMYK.
Another important color space is Adobe RGB (1998), which is designed among other things to incorporate most of the colors that can be printed via CMYK (see Figure 2.3). In the past, most digital cameras used sRGB; now an increasing number of models provide sRGB and Adobe RGB (1998). This makes Adobe RGB (1998) one of the better choices for photographers.
From Chapter 3:
Digital capture is more demanding than shooting film or transparencies. In fact, a variance of 1/10 of a stop can make the difference between success and a painful, difficult post-production process.
Digital capture is very sensitive to under- or over-exposure, and either of these can affect color in unexpected ways. I use a hand-held exposure meter more than ever. (An exposure meter is a device that measures light intensity and calculates shutter and aperture settings appropriate for a selected film/sensor ISO, or light sensitivity.) This is directly linked to the physical characteristics of digital camera sensors. Our eyes and brain see much differently than a digital sensor. Our eyes adjust to a scene with amazing flexibility, allowing us to see a range of brightness that is many times greater than any currently available recording device.
Digital sensors record images in terms of light levels. The brightest part of an image provides most of the information, and the darkest part the minority of information. This type of recording is linear in nature.
Some photographers think that now that they have digital, they can fix a poor exposure in Photoshop. But given the recording characteristics of digital sensors, any over-exposure will make your life difficult, if not downright miserable.
Like transparencies, information lost in the highlights is difficult, or impossible, to recover. And the highlights contain the majority of the information in your image! How do you tell when your exposure is correct? If you are in the studio, use a hand-held exposure meter. I recommend that you put your set-ups together the old-fashioned way–one light at a time, metering each light separately. This has of course been the subject of many books.
On location, you will often use the in-camera exposure meter to assist in setting your exposures. However, it is still best to back up your decision with information from a hand-held meter. If this is not practical, do try to use a range of exposures, from slightly under-exposed to slightly over-exposed (this is called bracketing). Many pro-level cameras offer this as an option and allow you to choose two- or three-frame bursts.
Next, many people use the LCD screen on the camera to preview the image–but this display is often limited in terms of correct brightness, contrast, and color. The best way to evaluate your exposure once the image is taken is to use the histogram display on your camera. Although this option also has some limitations, it is a much better indicator than the LCD display on the camera, particularly when you are in bright ambient lighting. As you gain experience with a particular camera, you’ll soon know how accurate your histogram is (see Figure 3.16).
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