Color Relativity: Which Display is Right for You? Posted on October 17th
Have you ever wondered what the differences are between the LCD displays offered by Apple, NEC and Eizo? We have taken a look at what we think are the most interesting displays on the market and have examined issues that involve price range, display dimensions and a spectrum of technical specifications.
Light panel technologies
Almost all displays are constructed with a front-panel and a back-light. The back-light transmits through the front-panel which is where the pixels filter light and wavelengths get divided and channeled into the three sub-pixels, respectively red, green, and blue, that form the display images. Each sub-pixel can be controlled independently to yield millions of possible colors for each pixel. see fig.1
Image of red, green and blue sub-pixels
There are two main types of front panels technologies: IPS= In-Panel Switching and PVA= Pattern Vertical Alignment. The IPS technology aligns the liquid crystal cells in a horizontal direction providing the panel with extra wide viewing angle capabilities, and minimal color shift when viewed from off-center. This is important because you don’t want to use a display where the colors change depending on the angle of vision. IPS panels use two transistors and are normally darker than displays with PVA panels because of energy lost to radiant heat.
The PVA panel displays use a technology where the liquid crystal material naturally exists in a horizontal state, removing the need for extra transistors. PVA panels have a greater shift in colors but are also considerably cheaper then their counterparts. The consequences of a cheaper PVA display are particularly evident when you color calibrate your display. You won’t be able to know at which exact incident angle the calibration device was placed on the display during the calibration, and therefore, you will never be sure of the precise viewing angle.
A note about the display contrast ratio
In the home entertainment world, it has been considered desirable to have the highest contrast ratio possible. When watching movies it might be great to have a contrast ratio of 100000:1 as proclaimed by some manufacturers. However the demanding photographer who wants to get an exact preview (soft-proof) of what will come out of the print-press or his color-calibrated ink-jet printer won’t find that the high contrast ratio makes an accurate soft-proof. When a photographer needs to soft-proof a picture, he needs to aim for the same contrast ratio as the final print. Most dye ink printers won’t print at a higher contrast then 500:1, and magazine printing is most often limited to a contrast ratio of 300:1 to 400:1. The LCD display’s native contrast ratio cannot be changed as it can with CRT displays, but with modern calibration software it’s possible to set a black level point and a max white point in order to control the contrast ratio.
Graph showing differences between Apple 30″ Cinema Display and the Adobe 98 RGB color-space. Grid: Adobe 98 RGB - Solid: Apple 30″
Luminosity
Depending on your work environment, you should choose a display capable of showing at least 110 candela (cd/m2). 110cd/m2 has become a industry standard in most retouching-studios. When you use a display in a dimly lit room, painted grey, 110cd/m2 or even less will be perfect, but if you use the display in a photo-studio or in a daylight environment, look for a display with the capability of showing a minimum luminosity of 120cd/m2 and preferably up to 250cd/m2 or higher, in order for the display to be able to show a clear image. The main factors that affect the perceived brightness of the display are the room lighting and the viewing distance. Once again the home-entertainment world has pushed up the demand for brightness, mainly because most TVs are located in bright rooms with all sorts of lighting.
Color-gamut
The color-gamut of a display is that portion of the color-space that can be reproduced. The color-gamut is dependent on the previously described hardware features. To find out how close a display’s color gamut is to a given work-space, such as the Adobe 98 color-space, you would first have to profile the display with a spectrometer and then compare the profile in an application like Apple’s ColorSync Utility. Some displays employ an extra wide color gamut that is close to 100% of the Adobe 98 RGB color space. A display with an extra wide color gamut is essential for conducting a precise soft-proofing when working in Adobe 98 RGB color-space.
Graph showing differences between Eizo CG241W and Adobe 98 RGB color-space. Grid: Adobe 98 RGB - Solid: Eizo CG241W
Out of gamut colors
With the latest generation of Epson ink it’s possible to print colors outside the Adobe 98 RGB color spaces. There’s nothing you can do to view those out-of-gamut colors on the display, although sometimes you can choose to change to a smaller color space. sRGB, for example, makes soft-proofing all the colors on your display possible, but when you print out the image, it will show less saturated colors because of the smaller sRGB color-space. To print with the most saturated colors, you would have to choose an extra large work-space, such as ProPhoto RGB, that is so large it contains colors that are not even visible to the human eye.
When making the decision to purchase, consider how important display size is in respect to color gamut. Apple makes the largest display at 30″, though a Apple display is far from always the best choice since they don’t use many of the advance technologies seen in Eizo and NEC displays. Both Eizo and NEC make displays that are being sold for up to $6000. While this is too expensive for most users, it’s possible to get a very good display such as the NEC 2190UXi or the Eizo CG211 for respectively $1,199.99 and $2,949.00 , both of these displays use IPS panels.
At Captureforce, we have just received the brand new Eizo CG241W which combines PVA technology with extra wide viewing capabilities. This display shows 98% of the Adobe 98 RGB color-space which is considerably more than the Eizo CG211. Please see the video of the Eizo CG241W ICC profile compared to the Adobe 98 RGB. The color-gamut of this display has been developed with special attention to cover the Adobe 98 RGB color-space. We can highly recommend this display as one of the best we have ever seen.
For more technical information about:
Eizo http://www.eizo.com/products/graphics/index.asp
NEC http://www.necdisplay.com/Products/Series/?series=171d9fbb-281e-44d8-be67-14d146e8ada0
Apple http://www.apple.com/displays/
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