The 23-inch Cinema HD Display comes with a much lower price tag of $899 while delivering some impressive specs, like 1920 x 1200 resolution, 400 cd/m2 brightness (same as the 30-inch) and a 700:1 contrast ratio, which is found in all of the models. The smaller 20-inch Cinema Display has 1680 x 1050 resolution and costs $599, and while dwarfed by its biggest brother, it's still a terrific size for photo work.
Contrast measures the ratio of light intensity between the brightest white and deepest black. A higher ratio means black levels and highlights are displayed more accurately. Look for a minimum of 400:1.
Viewing angle typically becomes more critical as the panel size increases. When LCD monitors are looked at from an angle, the brightness and color of an image can appear distorted. To compensate for that effect, many of today's displays are designed with wider viewing angles. A range between 120 and 170 degrees is typically sufficient.
Brightness is fairly obvious in terms of purpose, but not in how it's listed. Light output is typically measured in candelas per square meter (cd/m2). The higher the number, the brighter the screen. Look for a ratio of 200 cd/m2 or higher—but remember to calibrate your monitor before doing photo work. While a bright screen looks great to the eye, an incorrectly set monitor can deceive you when you're enhancing your images.
Color support, or the number of bits used to describe the color of a single pixel, should have a minimum depth of 8 bits, which is capable of showing the entire sRGB color space. Newer models support a wider color space, with some able to display the entire Adobe RGB color space.
DVI and HDMI interfaces transmit a digital signal for the best display quality. Digital displays will use one of these connections. DVI (Digital Visual Interface) only supports video, requiring separate sound cables for a complete audio/video hookup. HDMI (High-Definition Multimedia Interface) is smaller and simpler than a DVI connector, and uses a single cable to carry both audio and video signals from the source to the display. HDMI is most common on HDTVs while DVI is the standard digital connection for computer displays. Note that if you're upgrading your monitor but not your computer, your system may not have support for a digital display and you may need to upgrade your graphics card to connect your new display.