Which monitor should I buy?
Trying to come to terms with which monitor to purchase can confuse even the technically savvy. There are a lot of things to think about, not least of which is price, and while it’s safe to say that we all want great color, what kind of price tag does that come with and how do you know you’re really getting what your paying for? In the following post, I hope to shed some light on this topic and help draw some lines of distinction between the different technologies.
The three main types of LCD display panels:
TN (Twisted Nematic)
S-PVA (Vertical Alignment)
S-IPS (In Plane Switching)
Twisted Nematic (or TN) displays are your cheaper LCD screens and they currently dominate the computer monitor market. TN displays have very fast refresh rates in the range of 2ms to 5ms which make them ideal for gamers. But for high-end color-critical graphics, TN screens are really not in the game at all. These displays have the worst color reproduction, most limited viewing angles and skimpiest contrast ratios of any LCD panel. Definitely not the monitors for editing high-end digital photographs. Also, TN displays are limited to 6-bit per channel and therefore can not display the 16.7 million colors available in the 24 bit color gamut. In plain English, this means these monitors are incapable of even displaying the relatively small sRGB colorspace properly on the screen. So when you see those great deals on LCD monitors you now know why they are so inexpensive.
Vertical Alignment Displays (or VA/PVA) displays are really the starting point when considering monitors for use with photographic images. Though very capable, and boasting (arguably) the best contrast ratios, the biggest drawback to this type of display has to do with colors shifting at different viewing angles. Many manufactures may quote a large viewing angle (up to 178 degrees) but in my opinion that claim is no guarantee of color uniformity across the entire screen, making those numbers a bit misleading. Sitting directly in front of a VA monitor expect to see color shifts both left and right of center.
Wide gamut is another thing you will hear a lot about when researching monitors. While VA panels will faithfully reproduce the smallish sRGB space, what about wide gamut? (In the context of display technology, “wide gamut” is actually referring to the Adobe98 color space.) Many VA panel manufacturers state that their monitor can reproduce 95% or more of Adobe98. How do they do that? Well, there are two main ways to increase the gamut of the display. The mostly widely used method right now is simply to improve the quality of the cold cathodes use to backlight the display. The second method would be to switch from cold cathodes to more advanced (and expensive) RGB LED backlighting. Using RGB LED backlights has some strong advantages: thinner displays, wider color gamut and instantaneous startup with no warm up time and greater stability. LEDs also consume less power and many users say they like the quality of white light they produce over cold cathodes. RGB LED backlit monitors do have a higher cost of manufacture, but expect them to become more prevalent in the future as costs of production drop. One area of confusion to clear up regarding LEDs: If the monitor’s specs just refer simply to “LED” backlighting then they are using white LEDs to backlight, not the RGB variety. There’s a difference. White LEDs will not improve the color gamut.
Another big selling point you may hear regarding VA displays: 10-Bit lookup tables (or 10-bit gamma correction). 10-bit is a buzzword manufacturers love to use whenever possibly, but just be aware that the above terms do not mean the monitor itself is “true” 10-bit. Instead, 8-bits per color is passed through a 10-bit lookup table and then a new, better 8-bit version of the image is passed on to be displayed. Because all but a very, very few VA panels are true 10 bit per color you can use them off of a standard video card. If you want true 10-bit then you’ll be moving up the food chain (and the price bracket as well). Which brings us to IPS panels—the current gold standard of color critical displays.
In Plane Switching (or IPS) displays are the top-of-the-line LCD screens currently available for viewing and editing photographic images. Why? One reason is 10-bit technology—a growing number (but not all) of IPS monitors are capable of true 10-bit display (I’ll have more to say on the subject of10-bit later in this post). Another reason: IPS panels have the best viewing angles. Note that I said best without giving any spec sheet numbers—I, like a lot of people, am growing leery of specs. (I think specmanship is an actual class taught in the school of marketing these days.) Case in point: the specs of a lot of VA monitors will read very similar to IPS monitors—similar viewing angles, similar color reproduction claims. But sit in front of either and you’ll usually be able to spot differences right away–and that’s what you are paying for. An IPS display will show more consistent color across differing viewing angles than VA monitors of similar specs. But not all IPS monitors are the same of course. For example, some IPS displays are calibrated at the factory specifically to ensure they are color consistent across the screen, and extras like those factory calibrations typically run up the cost. That leads to a relatively wide range of IPS pricing–I’ve seen same-sized IPS monitors for as little as $499 and as much as $1700.
Getting what you pay for
To see what a good but lower-priced monitor is capable of, here at ColorByte we purchased a Dell UltraSharp U2410 for $499. It’s an IPS 10Bit (1.07 billion colors) wide-gamut display (up to 96% of Adobe98). It has a 178 degree viewing angle and while sitting in front of it I do not see any color shift due to moving my head from side to side to view the full width of the display (something I haven’t seen with similarly priced VA monitors). But while viewing angles are consistent, how about color constancy across the screen? Dell states that this monitor is “calibrated at the factory to be within 5 delta E of color accuracy”. While Dell doesn’t really define exactly what that statement means, we measured a uniform gray swatch across the screen from left to right and found the accuracy to be about 5 delta E, so we’re guessing that’s the color accuracy they’re referring to. 5 Delta E is visible to the naked eye, and we can clearly make out on our gray image that the left area of the screen has a slight green cast compared to the slightly warmer right side. For $499, this was something we were willing to live with. After all, in this case we didn’t set out to find the best picture money could buy–we set out to find the cheapest IPS 10 bit display money could buy. And this monitor seems to live up to its specifications. You can see the monitor spec here http://accessor ies.us.dell.com/sna/productdetail.aspx?c=us&l=en&cs=19&sku=320-8277&baynote_bnrank=49&baynote_irrank=0&~ck=baynoteSearch
Why did we choose this monitor: From what we could tell at the time (about a year ago), this Dell panel was very similar to what Apple was then selling as their Cinema Display which then sold for $999. The current Apple Cinema Display, by the way, has changed quite a bit: it’s now a 27” IPS, 8-bit monitor, with white LED backlighting (and still sells for $999). The current Cinema Display also has a 12ms response time compared to 6ms for the Dell. (Anything above 8ms can cause motion blur).
Remember that 5 Delta E difference from left to right on our Dell monitor? How much is it worth to you to get rid of that? If you said a lot, better break out your wallet. This is where we start to consider offerings from LaCie and Eizo.
Just like with any product, when you start to look at the high-end you pay a price for each step in the quality. This holds true for both PVA and IPS displays. These panels go through rigorous testing with only the best of the best making the cut and naturally you pay for that. You also pay for control, and the top monitors all have user controls that go beyond those on the bargain ones. You’ll appreciate these controls when trying to achieve a good screen to print match because at their default settings these panels are so much brighter than a piece of paper. Even calibrating the monitor to a lower luminance is no guarantee that you can (at least easily) reproduce the subdued brightness of a print. Easily accessed controls that allow you to quickly tone down the monitor when soft-proofing can be invaluable.
With so many factors involved, and specs that often don’t tell the whole story, choosing a high-end monitor can be daunting–especially since it is nearly impossible to compare different displays side by side in a realistic testing environment where you can make a clear distinction of one from another. This is why when writing this article I talked with an expert: John Fitzpatrick of ColorMall (www.colormall.com). John sells all the top monitor offerings and I wanted to get some advice on what to buy for various price ranges. In the under $900 dollar category John recommends the LaCie 324, a high-end PVA panel. (This product will soon be replaced by a more expensive LaCie model, but a new offering from Eizo, the Eizo SX2262W will also fit right into that price point). For IPS displays John recommends the LaCie 324i which comes in around $1139. If money is no object and you just want the best picture you can get the Eizo CG243W delivers at just under $2000.
Lets talk 10-Bit
10-bits per channel is often touted as a must have feature of a high end monitor, but there’s enough information and misinformation about the subject to confuse just about anyone. Let’s try to break it down. A 10 bit compatible monitor supports 10 bits per color plane (1.07 billion colors) through a Display Port connector. No other connection type is compatible with a 10 bit band width. You must also have a 10-bit compatible video card. (You should make sure this video card has been tested with your exact computer/OS/monitor configuration or you may find that it will not support 10 bits due to some driver or hardware limitation). Now the really hard stuff. Just because your monitor and your video card are now 10-bit doesn’t mean the image you see on the screen through your application will be 10-bit. Yep, that’s right, software matters and the application has to specifically support OpenGl (Open Graphics Libraries) in 10-bits to work with a 10-bit image. Right now the only photographic editing application I know of that will utilize a 10-bit workflow is Photoshop CS 5 (on both Snow Leopard on the Mac and Windows 7 on the PC). On Windows 7’s Photoshop CS5 you have some setup required to enable 10-bit. This document from Eizo explains the procedure: http://www.eizo.com/global/support/compatibility/monitors/20.pdf . On the Mac, Photoshop CS5 requires no special procedures, but make sure you have all the proper updates for the OS and for the video card.
Getting 10-bit to work can be confusing, expensive and prone to driver incompatibilities (I know of some very persistent users who have waited over a year to make their configurations work). And, practically speaking, all for one application (Photoshop). Though the expanded color range of a 10-bit display can certainly eliminate display banding in gradations and possibly aid in seeing subtle details in hi-bit images, in my opinion, 10-bit isn’t the holy grail when it comes to choosing a monitor. The overall quality of the panel and its consistency across the screen (and at different viewing angles) are at least as important considerations. If you solely justify the money simply based on seeing a 10-bit image you will undoubtedly be disappointed.
What the future holds
After all this talking about LCD’s I can’t close without a quick look at the future. Before we know it LCDs will be a thing of the past replaced by a new technology called OLED (Organic LED). OLED isn’t a backlit LED behind an LCD panel. Instead, the LED actually lights the pixel (no backlighting needed) which allows for much better control of color and contrast. There are very few of these on the market today: Sony introduced a 25” display that sold for about $30,000. But, I hear LG should soon have a 17” one for about $2000 and smaller ones are now popping up in cell phones and hand held gaming machines. So just about the time we figure out this whole LCD thing we get to start all over again. So stay tuned!