When the first production 4K displays appeared at the 2012 CEDIA Expo, computer enthusiasts everywhere wondered, “When will this land on my desktop?”
A number of 4K screens have launched between then and now (they were particularly prevalent at CES this year). But Asus was one of the first to offer 3840x2160 resolutions at up to 60 Hz through its tiled PQ321Q Ultra HD monitor. A lot of the other 4K screens we've been shown only do 30 Hz, or they employ lower-quality panels. You have to pay attention to those specifications; they especially matter when it comes to gaming.

Not only does Asus' PQ321Q offer the highest pixel count of any monitor I've reviewed to date, but it also delivers a generous 31.5-inch diagonal viewing area.
Of course, the products that show up first to market are invariably accompanied by their own challenges, too. There's a distinct possibility that you might need a new graphics card to feed the PQ321Q's two 1920x2160 panels, for starters. You also have to consider how tiny the objects on your desktop will become at 3840x2160. As we move through our review, we'll cover some of the gotchas we encountered and how to address them.
But first, let's dig into the PQ321Q's specs and underlying screen technology.
| Brand | Asus |
|---|---|
| Model | PQ321Q |
| Street Price | $3499 |
| Panel Type | IGZO |
| Backlight | W-LED, edge array |
| Screen Size | 31.5 inches |
| Max Resolution | 3840x2160 |
| Max Refresh Rate | 60 Hz |
| Aspect Ratio | 16:9 |
| Response Time (GTG) | 8 ms |
| Brightness | 350 cd/m2 |
| Speakers | 2 x 2 W |
| VGA | - |
| DVI | - |
| DisplayPort | 1 (v1.2) |
| HDMI | 2 (v1.4a) |
| Audio In | 1 (3.5 mm) |
| Headphone | 1 (3.5 mm) |
| USB | - |
| Panel Dimensions W x H x D w/base | 29.5 x 19.3 x 10.1 in 750 x 489 x 256 mm |
| Panel Thickness | 1.4 in / 35 mm |
| Weight | 28.66 lbs / 13 kg |
| Warranty | Three years |
There's nothing earth-shattering about the screen's specifications, except of course its 8.3 million-pixel count! Alright, the number is actually 8,294,400, corresponding to a density of 140 ppi. That’s still below the number Apple uses for Retina branding on its MacBook Pros, though the official minimum depends on how far away from the screen you're expected to sit. Regardless, 140 ppi is still quite a bit better than the 109 ppi we get from 27-inch QHD monitors.
The other technology we're reviewing for the first time at Tom's Hardware is IGZO (yes, we did use Asus' screen in Gaming At 3840x2160: Is Your PC Ready For A 4K Display?, but that wasn't a review of the panel specifically). While all of the QHD monitors we test are some flavor of IPS, this one is based on a panel based on IGZO technology, sourced from Sharp. Bear in mind that the low-cost 4K screens we reported on from CES 2014 utilize TN screens.
IGZO stands for Indium Gallium Zinc Oxide. It was invented in 2003, but didn’t find its way into production until 2012. IGZO’s main claim to fame is increased molecular mobility, which can be between 20 to 50 times greater than amorphous silicon. What are we talking about? The actual substance inside each sub-pixel of an LCD display.
LCD is a light valve technology, meaning that a constant light source (the backlight) is manipulated by millions of tiny valves to produce varying colors and intensities of light. Those valves are much of what differentiates the various panel types. TN and IPS panels use silicon as their valve material. The molecules in each sub-pixel are twisted to either block or admit light. The speed and efficiency at which this occurs is what drives progress. IGZO is simply a material that responds more quickly to input and requires less current. As a result, the controlling transistors can not only be smaller, but they can also be transparent. This means less power is consumed, and the panel is both thinner and lighter. It's no coincidence that Apple's iPad Air employs an IGZO display.
Up until recently, IGZO was found in all of the 4K displays we were hearing about, including HTDVs from Samsung, Sony, and LG. That's not to say all of the panels were made by Sharp; the technology is simply licensed to other panel manufacturers. And remember that IGZO only refers to the transistor and liquid crystal layers of the screen. The backlight and arrangement of pixels differ from display to display. IGZO simply makes smaller pixels possible, simultaneously offering theoretically better response times.
The only clue that there's something special inside the PQ321Q’s box is its large size. Otherwise, Asus' packaging looks like pretty much every other monitor carton you’ll see on the shelf at your local computer store. It’s packaged securely in Styrofoam and well-protected from all but the worst shipping abuse.
Included in the box is a large power brick, a DisplayPort cable, a nine-pin-to-3.5 mm RS-232 adapter, cable ties, and a printed manual. The base is in two pieces and must be assembled and attached to the panel with nine screws; Asus provides the hex key you'll need. This is the first screen we’ve seen in a while that requires tools to set up.
Product 360

Looking at the monitor head-on, the screen takes on a minimalist appearance, with nothing to distract you from the image except a small Asus logo. The control keys are hidden around the upper-right edge. The bezel is 23 mm wide all around and made of a textured black plastic that feels solid and high in quality. The base and upright are made of the same material. Available ergonomic adjustments include 30 degrees of tilt, 90 degrees of swivel, and 150 mm of height. There is no rotation adjustment, but you can use the panel in portrait mode if you attach the upright appropriately or use a different mounting system. To that end, there’s a 200 mm VESA mount around back.

The control keys are clearly labeled, though that doesn’t do you much good since they aren't visible from the front. You’ll have to operate the buttons by feel alone. They do at least return a satisfying click when you press them. There are small raised portions on the power and menu keys, which would logically help you keep your bearing. But even after working with the PQ321Q for a while, we found ourselves pressing the wrong key fairly often. If Asus could get a little pop-up guide in the screen, that'd be a big improvement.

The 150 mm height range is quite generous. Sliding the monitor up and down is tricky though, since the movement is a bit sticky and the panel is very heavy. Perhaps it'd loosen up over time. Asus includes ties and clips to help you clean up cable clutter.

At less than one-and-a-half inches thick, the PQ321Q is a relatively slim panel. You can see a small cable tie protruding from the back of the upright.

The rear of the display is all about function. There’s plenty of ventilation and the two input panels are clearly labeled. The left one is for the power cord and includes an on/off switch. The right panel contains the two HDMI ports and the DisplayPort input. Below that there are two 3.5 mm audio jacks, one for input and one for headphones. Finally, there is a USB port hidden by a plastic plug, which is for firmware updates and service only.
Integrated speakers are fed by the 3.5 mm audio input. They sound bright and small like the majority of drivers built into monitors. A dedicated sound system connected to your PC's audio subsystem is always a better choice. The final input is a 3.5 mm RS-232 control port. The required adapter is included and there is a full list of command codes in the manual. Every function in the OSD can be addressed via serial interface.
The PQ321Q’s menu system is fairly complete. Our main complaint is that it takes up most of the left side of the screen and cannot be moved or reduced in size. To measure a window pattern, you have to place the meter a little right of center. It also has the unfortunate habit of disappearing after only 15 seconds, which is major pain when you’re trying to tweak calibration settings. The timeout value is not adjustable, either.
Here’s where you’ll spend most of your time.
The first thing you’ll notice is a black level control. This is separate from the brightness slider, which actually sets the backlight level. We appreciate this feature and wish it were standard on all computer monitors (after all, it's very common on consumer TVs). Out of the box, the backlight is set to maximum. You’ll have to throttle it back quite a bit to match a 200 cd/m2 output level. It also has very poor resolution. Each click represents about 12 cd/m2, which makes setting a precise luminance point very difficult. The upside is it has a very wide range.
Contrast is set to 30 by default. We backed it off one click to improve grayscale performance. Settings above 30 will clip detail. The useful minimum for the black level slider is 28. Colors and Tint will change saturations and the hue of secondary colors. These controls are best left alone. Sharpness is also best left at its default of 12. Higher settings produce visible edge enhancement.
Selecting Color Adjustment brings up the next menu.
There are three color modes, Standard, Vivid, and sRGB. Vivid creates an over-saturated cartoonish look and should be avoided. sRGB is fairly accurate, but it locks out all of the color temperature adjustments. So, we performed our tests and calibration using Asus' Standard mode. Gamma is set to Standard by default, which is not ideal. Changing it to 2.2 makes the tracking much better.
You can adjust the overall color temp with the different White Balance modes. Preset opens up an option that lets you set the color temp by Kelvin value, and User unlocks the RGB sliders.
We’re glad to see both high and low RGB adjustments included. This, combined with extremely fine resolution, allows precise control of the white point at every brightness level. The out-of-box grayscale performance is quite excellent. But we were able to make it even better using this menu.
The OSD is available in seven different languages. Input selection can be done here or with the bottommost side control key. Audio Select specifies the sound source (either HDMI or 3.5 mm mini-plug). The Audio Input Level worked fine for us at the .5 V setting. Baud Rate refers to the RS-232 control port. Its setting depends on the device you're connecting it to. DisplayPort STREAM is important. It’s set to multi by default, which is required when sending a native 3840x2160 signal from your computer.
You can use the PQ321Q in portrait mode if you attach it that way to the included base. Then, you have to reorient the image manually. Standby Mode can reduce power consumption in standby when set to Low Power. If you do this, it will take longer for the monitor to power on. To maintain access to the RS-232 interface, you need to leave Standby Mode set to Standard. Off If No Operation turns the display off after four hours of inactivity.
We didn’t take a shot of the PBP menu because we didn’t have two sources connected to activate it. When you use the picture-by-picture function, the images are shown side by side using the source resolution. If one source is connected via DisplayPort, you have to set that input to Single Stream mode.
Screen Motion offers two patterns to combat image retention. This isn’t really an issue for LCD displays. Size determines the aspect ratio of the image. In Wide mode, the PQ321Q scales all incoming resolutions to 3840x2160. In our resolution test patterns, we were impressed with how well it accomplished this. Most monitors roll off the one-pixel pattern so it looks distorted. With a 1920x1080 signal from our pattern generator, this monitor rendered it perfectly.
Selecting Information brings up the final screen.
This gives you a quick look at key settings and indicates the input resolution and refresh rate at the bottom.
Asus PQ321Q Calibration
This monitor barely needs a calibration since its out-of-box grayscale and gamma are pretty good. If you don’t have a meter, we recommend you set Color Mode to Standard, White Balance to Preset, and Gamma to 2.2. Then reduce the Brightness (backlight) to taste.
If you want to achieve near-perfection (as we did), it will take some back and forth work between the Brightness, Contrast, and Black Level controls. They affect each other, so you’ll need to exercise patience to find the right balance. The RGB sliders include both high and low adjustments, and these interact as well. While the PQ321Q is fairly easy to calibrate, it does require a bit more effort than most screens because of its fine control resolution.
| Asus PQ321Q Calibration Settings | |
|---|---|
| Brightness | 15 |
| Contrast | 29 |
| Black Level | 30 |
| Color | 30 |
| Tint | 30 |
| Sharpness | 12 |
| Color Mode | Standard |
| White Balance | User |
| R-Contrast | 248 |
| G-Contrast | 252 |
| B-Contrast | 256 |
| R-Offset | 2 |
| G-Offset | 2 |
| B-Offset | -6 |
| Gamma | 2.2 |
Installation
Like any bleeding-edge technology, the PQ321Q isn't as easy to use as simply plugging it in and enjoying. There are a few requirements that must be satisfied first.
First is your choice of graphics card. Obviously, it needs to support a resolution of at least 3840x2160. That’s the easy part, since a quick search on Newegg produced 59 results ranging in price from $65 to $1020. But don’t close that browser tab just yet. You can drive this particular screen using one DisplayPort or two HDMI interfaces.
If you read Gaming At 3840x2160: Is Your PC Ready For A 4K Display?, then you know the PQ321Q is not a typical LCD panel by any stretch. The real trick is achieving a 3840x2160 picture at a refresh rate of 60 Hz using the connection options that Asus gives you.
As far as your graphics card is concerned, the PQ321Q is actually two 1920x2160 panels seamlessly connected together. No, you won’t see a line down the middle. In fact, the only visual giveaway is that the two halves turn on in sequence. You’ll also see them refresh separately when you change display settings. The reason for this is that there are two scalers at work behind the scenes. Each one is responsible for half of the image. Why two? Because there is still no single-scaler solution that supports Ultra HD at 60 Hz.
None of this has any bearing on the monitor’s day-to-day functionality, though. So, returning to your choice of graphics card, you’ll need two HDMI outputs (or another digital connection adapted to HDMI) or one DisplayPort 1.2 output. Why 1.2? Because multi-stream functionality is required to make this work, and revision 1.1 doesn’t have that.
Out-of-the-box, our sample monitor was set for DisplayPort MST. We used a GeForce GTX Titan for testing, which supports DisplayPort 1.2 and multiple digital outputs that can be adapted to HDMI, so either configuration would have worked. Most folks are going to use DisplayPort though; it's just easier. Since the graphics card sees the PQ321Q as two monitors, you need Surround mode (on an Nvidia card) enabled. This happens automatically with the latest GeForce drivers.
Alright, so the DisplayPort setup is easy enough. You use one cable, a compatible output, and so long as the monitor is set to accept an MST signal, it'll run at 3840x2160 at 60 Hz. Dual HDMI connections can be a little trickier, since most graphics cards have one HDMI output, but rarely two. That's what you need, though, to provide enough bandwidth for both 1920x2160 panels at 60 Hz. Of course, the HDMI 2.0 specification was just recently released, so we expect future screens to get the throughput they need through a wider pipe. Bottom line: pick a video card that supports DisplayPort 1.2 with MST. It’s by far the most straightforward way to make the PQ321Q work.
Windows Image Quality
A monitor this expensive will appeal to well-heeled gamers and graphics professionals. Either way, you will have to live with this thing in Windows at least some of the time, so we played around in a number of applications to gauge whether Ultra HD would enhance or diminish our experience.
If you’ve made the jump from FHD to QHD, then you know that text and icons become much smaller. How you live with that depends on the quality of your eyesight. With most QHD screens, we have to employ at least some font scaling. Windows font scaling is poor at best. Text does get bigger, but it softens in the process, making it just as difficult to read as at its native size. The same thing applies to the PQ321Q. Our 200 cd/m2 calibration suddenly looked too dim because text and other on-screen objects became blurred. Turning up the backlight help, but in my opinion, using Windows 7 like many enthusiasts still are, image quality takes a step backwards. This is in no way the monitor's fault. Windows 8.1 does add scaling enhancements for high-DPI displays and per-screen scaling adjustments. However, scaled text still looks distractingly blurry to me.
The best way to retain clarity is to employ scaling options in your individual apps. Every browser has its own scaling function. These work much better than Windows’ global one. Productivity apps are the same; sizing windows to taste or setting screen font scaling options almost always results in a better image than using the OS.
Where this screen excels over all others is in graphics. Viewing a photo on the PQ321Q is an almost religious experience. Even a few inches away, you can’t see the pixel structure. A photo shot at the display’s native resolution or higher is simply stunning. Color gradations are super-smooth, jaggies are non-existent, and everything takes on a vibrancy you just don't see on a lower-resolution monitor. Gaming inspires the same reaction. The depth and clarity of the on-screen environment achieves a realism that’s leaps and bounds better than even the best QHD monitor.
To measure and calibrate monitors, we use an i1Pro spectrophotometer and version 5.1.2 of SpectraCal’s CalMAN software.

For patterns, we employ an AccuPel DVG-5000 video signal generator. This approach removes video cards and drivers from the signal chain, allowing the display to receive true reference patterns. Connections are made via HDMI.

The AccuPel DVG-5000 is capable of generating all types of video signals at any resolution and refresh rate up to 1920x1080 at 60 Hz. It can also display motion patterns to evaluate a monitor's video processing capabilities, with 3D patterns available in every format. This allows us to measure color and grayscale performance, crosstalk, and ghosting in 3D content via the 3D glasses.
The i1Pro is placed at the center of the screen (unless we’re measuring uniformity) and sealed against it to block out any ambient light. The Accupel pattern generator (bottom left) is controlled via USB by CalMAN, which is running on the Dell XPS laptop on the right.
Our version of CalMAN Ultimate allows me to design all of the screens and workflows to best suit the purpose at hand. To that end, we’ve created a display review workflow from scratch. This way, we can be sure and collect all the necessary data with a concise and efficient set of measurements.
The charts show us the RGB levels, gamma response, and Delta E error for every brightness point from zero to 100 percent. The table shows us the raw data for each measurement. And the area in the upper-left tells us luminance, average gamma, Delta E, and contrast ratio. The individual charts can be copied to the Windows clipboard to easily create graphics for our reviews.
Every primary and secondary color is measured at 20, 40, 60, 80, and 100 percent saturation. The color saturation level is simply the distance from the white point on the CIE chart. You can see the targets moving out from white in a straight line. The further a point is from center, the greater the saturation until you hit 100 percent at the edge of the gamut triangle. This shows us the display’s response at a cross-section of color points. Many monitors score well when only the 100 percent saturations are measured. Hitting the targets at the lower saturations is more difficult, and factors into our average Delta E value (which explains why our Delta E values are sometimes higher than those reported by other publications).
Uncalibrated
Before calibrating any panel, we measure zero and 100 percent signals at both ends of the brightness control range. This shows us how contrast is affected at the extremes of a monitor's luminance capability. We do not increase the contrast control past the clipping point. While doing this would increase a monitor’s light output, the brightest signal levels would not be visible, resulting in crushed highlight detail. Our numbers show the maximum light level possible with no clipping of the signal.
Our comparison group consists of the last six desktop monitors reviewed at Tom’s Hardware.

The PQ321Q slightly exceeds its claimed spec of 350 cd/m2. There is more than enough light available from the display for just about any environment.
Unfortunately, the effect on black level is negative.

A result of .5088 cd/m2 is fairly high compared to the competition. And it is higher than the Planar’s value, even though that screen is almost 100 cd/m2 brighter.
Here’s the final contrast result.

Asus' PQ321Q won’t be sold on the basis of its contrast performance. Since this is our first IGZO-based display, we can’t say if low contrast is inherent to the technology. We currently have Dell’s 4K screen in the lab as well, and we expect to be looking at Sharp’s model soon. After that parade of Ultra HD decadence, we'll know if IGZO gives up contrast superiority to IPS, or if Asus simply made influencing design decisions.
We believe 50 cd/m2 is a practical minimum standard for screen brightness. Any lower and you risk eyestrain and fatigue. Many monitors do measure under that level. While the comparison chart shows the absolute lowest brightness for a given monitor, we also comment on the contrast and black level results at a 50 cd/m2 setting.
The PQ321Q has a maximum output of 49.7378 cd/m2 when brightness is set to zero, which is right at our standard! We’ve been a bit concerned about the trend towards brighter monitors because some of them can’t be turned down to 50 cd/m2, which is preferable in a dark environment. Fortunately, the PQ321Q has enough luminance range to reach both very high and low brightness levels. For these tests, we only turned down the brightness. Black Level and Contrast were left alone.

The PQ321Q’s black level improves mightily when you turn the backlight down. A result of .0729 cd/m2 puts it right in the middle of the pack.

The on/off contrast ratio stays about the same whether the backlight is turned all the way up or down. The image is very consistent in quality regardless of your preferred light level. Even though the contrast numbers are on the low side, perceived contrast is pretty good thanks to spot-on gamma performance which we’ll talk about on the next page.
After Calibration
Since we consider 200 cd/m2 to be an ideal point for peak output, we calibrate all of our test monitors to that value. In a room with some ambient light (like an office), this brightness level provides a sharp, punchy image with maximum detail and minimum eye fatigue. It's also the sweet spot for gamma and grayscale tracking, which we'll look at on the next page. In a darkened room, many professionals prefer a 120 cd/m2 calibration. We find this makes little to no difference on the calibrated black level and contrast measurements.
Hitting the 200 mark on the PQ321Q is tricky because the Brightness control is extremely coarse. Each click of the 30-step slider results in a change of almost 12 cd/m2. After tweaking the Contrast control, we got it to settle at 197.3585 cd/m2.
You’ll want to lower the Black Level control to a point just before detail is clipped. Anything below 28 and you won’t see the darkest steps. We used 30 so we could comfortably see detail in a moderately-lit room.

This is a good but not great result. We are glad that calibration doesn’t seem to cause any penalty in black level. Of course, the changes made to grayscale are small because the PQ321Q has such good out-of-box accuracy. And we do recommend calibration, especially considering the PQ321Q's price. If you’re going to put a $3500 monitor on your desk, it should perform at its absolute best.
Here are the final calibrated contrast numbers.

Again, the PQ321Q’s on/off contrast ratio comes in just under 700:1. Compared to most of the screens we’ve tested, that's a below-average result. At least it has excellent gamma to improve its perceived contrast.
ANSI Contrast Ratio
Another important measure of contrast is ANSI, which we measure using a checkerboard pattern of sixteen zero- and 100-percent squares. This is somewhat more real-world than on/off measurements because it tests a display’s ability to simultaneously maintain both low black and full white levels, and factors in screen uniformity. The average of the eight full-white measurements is divided by the average of the eight full-black measurements to arrive at the ANSI result.

It always impresses us when a display maintains an ANSI contrast ratio close to its on/off one, demonstrating the use of high-quality components, particularly the grid polarizer. Light leakage between dark and light portions of the image is almost non-existent.
The majority of monitors, especially newer models, display excellent grayscale tracking (even at stock settings). It’s important that the color of white be consistently neutral at all light levels from darkest to brightest. Grayscale performance impacts color accuracy with regard to the secondary colors: cyan, magenta, and yellow. Since computer monitors typically have no color or tint adjustment, accurate grayscale is key.

This is the PQ321Q’s Standard color mode with the grayscale preset at 6500K. The graph shows a slightly warm result, where red rises slightly with brightness. If you look at the Delta E errors, however, they are all under three, which means they’re invisible. We were perfectly happy to use Asus' display in an uncalibrated state.
Since our goal is always perfection, we used all of the available controls to try improving the grayscale result.

This is a near-perfect chart. The Delta E errors at 30, 70, and 80 percent are only .07! And every other level is well below one, except zero percent. We’ve never seen any display, of any type, turn in such strong results. We attribute the performance to Asus' high and low RGB sliders and the extremely precise resolution they enable.
Here’s our comparison group of the last six desktop monitors reviewed at Tom’s Hardware.

We said in our review of the Dell P2714T that it was a display that didn’t need calibration. Now we’re adding the Asus PQ321Q to the same list. An average Delta E error of 1.48 is pretty much negligible. You won’t be able to see it with a naked eye. Only our i1Pro knows the difference.
The calibrated result is even more impressive.

Considering the error at zero percent is 2.16 Delta E, the average figure of .53 is almost unbelievable. If you take that brightness level out of the equation, the average drops to an incredible .37!
Gamma Response
Gamma is the measurement of luminance levels at every step in the brightness range from 0 to 100 percent. This is important because poor gamma can either crush detail at various points or wash it out, making the entire picture appear flat and dull. Correct gamma produces a more three-dimensional image, with a greater sense of depth and realism. Meanwhile, incorrect gamma can negatively affect image quality, even in monitors with high contrast ratios.
In the gamma charts below, the yellow line represents 2.2, which is the most widely accepted standard for television, film, and computer graphics production. The closer the white measurement trace comes to 2.2, the better.

The PQ321Q’s gamma tracking is almost perfect except for 10 and 90 percent, which are just a bit too bright. The error at 10 percent represents only .72 cd/m2 and the 90 percent error is 1.85 cd/m2. That's too tiny to see without the aid of instruments.
Here’s our test group again for the gamma comparisons.

A variance of .21 indicates very tight gamma tracking. You can see from the graph above that the PQ321Q’s gamma is extremely accurate. You’ll need to change the gamma preset from Standard to 2.2 to accomplish this. This really helps improve image quality, even though the measured contrast is on the low side.
We calculate gamma deviation by simply expressing the difference from 2.2 as a percentage.

The PQ321Q is only 1.81 percent off the target value of 2.2, matching the very best displays we’ve tested. Along with grayscale, this is an area where we’re seeing consistent improvement in newer screens.
Color gamut is measured using a saturation sweep that samples the six main colors (red, green, blue, cyan, magenta, and yellow) at five saturation levels (20, 40, 60, 80, and 100%), providing a more realistic view of color accuracy.

The PQ321Q’s color performance is not quite as good as what we saw in the grayscale and gamma tests. The blue/magenta/red side of the gamut is slightly undersaturated. In addition, all colors except cyan are clocked away from their targets. You can see in the luminance chart that blue, magenta, and, to a lesser extent, red are bumped up to compensate. If you check out familiar images like fleshtones and sky, they look reasonably accurate. The errors increase as you go up in saturation.
Let’s see how Asus' screen stacks up against the competition.

An average error of 2.55 Delta E is beneath the threshold of visibility, but some of the problems at higher color saturations can be seen by the naked eye. The range of values is .47 to 7.53 Delta E. We’d prefer to see greater consistency in a monitor selling for $3499.
Gamut Volume: Adobe RGB 1998
There are basically two categories of displays in use today: those that conform to the sRGB/Rec 709 standard like HDTVs, and wide-gamut panels that show as much as 100 percent of the Adobe RGB 1998 spec. We use Gamutvision to calculate the gamut volume, based on an ICC profile created from actual measurements. The chart shows the percentage of both sRGB and Adobe RGB 1998 gamuts.

The PQ321Q is a Studio RGB-only display. It is accurate enough for professional use, but many will prefer the wider Adobe RGB 1998 gamut available in screens like Asus' PA279Q. We’re sure it’s only a matter of time before an Ultra HD panel becomes available in wide-gamut form. For now, we have to be satisfied with a monitor that looks great in gaming and multimedia applications.
Each flavor of LCD technology brings a different off-axis viewing experience. Because the emitted light is polarized, there will always be some variation in either brightness, color, or both whether you're talking about TN, IPS, or in this case, IGZO. The type of backlight also affects the result.
Asus' PQ321Q demonstrates excellent performance in the vertical plane, while the horizontal shows a slight shift towards green. Luminance is preserved very well and detail holds up beautifully. We can see the darkest steps in all of the patterns without difficulty.
Screen Uniformity: Luminance
To measure screen uniformity, zero- and 100-percent full-field patterns are used, and nine points are sampled. In a change from previous reviews, we’re now comparing the results to other monitors we’ve measured. First, we establish a baseline measurement at the center of each screen. Then the surrounding eight points are measured and their values expressed as a percentage of the baseline, either above or below. This number gets averaged. It is important to remember that we only test the review sample each vendor sends us. Other examples of the same monitor can measure differently in this metric.
First up is black field uniformity.

We're shown yet another excellent result. We can’t see the variations reported by our meter. Looking at the individual measurements, the hot spots occur in the upper-left and lower-right portions of the screen. Increasingly, we're finding 10 percent to be a good standard by which to judge screen uniformity. Beyond that and you’ll likely see the hot spots; below 10, you won’t.
Here’s the white field measurement.

The PQ321Q turns in another excellent result. There are no visible variations in brightness anywhere on the screen. By the numbers, the center is actually brighter than the surrounding areas, except for bottom-center, which is the brightest of all. That's all according to our meter. Visually, it’s perfect.
Screen Uniformity: Color
To measure color uniformity, we display an 80-percent white field and measure the Delta E error of the same nine points on the screen. Then we subtract the lowest value from the highest to arrive at the result. A smaller number means a display is more uniform. Any value below three indicates a variation that is invisible to the naked eye.

Even though our measured result is nearly as high as Dell's P2714T, where we could just see the color shifts, we can’t see any white balance differences on the PQ321Q. The greatest error is in the top left at 3.04 Delta E. This barely just cracks the visibility point.
To perform these tests, we use a high-speed camera that shoots at 1000 frames per second. Analyzing the video frame-by-frame allows us to observe the exact time it takes to go from a zero-percent signal to a 100% white field.
The pattern generator is placed at the base of the monitor so our camera can capture the precise moment its front-panel LED lights up, indicating that a video signal is being received by the monitor. With this camera placement, we can easily see how long it takes to fully display a pattern after pressing the button on the generator’s remote. This testing methodology allows for accurate and repeatable results when comparing panels.
Here’s a shot of our test setup. Click on the photo to enlarge.
The brighter section of the camera’s screen is what actually appears in the video. You can see the lights of the pattern generator in the bottom of the viewfinder. We flash the pattern on and off five times and average the results.
Here’s the screen draw result.

The screen draw time matches most of the IPS monitors we’ve tested. But a 4K monitor probably won't be the choke point for performance when you're driving this many pixels. Even with the fastest video cards, you won't be pushing more than 60 FPS in most games.
Although the IGZO technology Asus is using offers theoretically faster response times, there are obviously other factors in the signal chain preventing measurable gains. At least for now, it’s safe to say that 4K monitors aren't the fastest option for fast-paced gaming.
And here are the lag results.

This is pretty much expected performance for a 60 Hz IPS screen. And since Asus' PQ321Q is the first IGZO-based display in our chart, it gives us a baseline for that technology, too. We don't anticipate these input lag measurements being an issue until modern graphics subsystems become more powerful. And the display's processing power matters as well. The control circuitry needs to catch up before the technology's advantages are fully realized.
Covering the latest and greatest technology is what we do, and we enjoy most of the hardware we get our hands on. Asus' PQ321Q represents the highest of high-tech in computer monitors right now. And as we saw at CES, Ultra HD is the next big thing in displays. Despite the sub-$1000 TN solutions introduced at the show, Asus' screen remains a premium product for the most discerning enthusiasts. This monitor (and indeed 4K technology as a whole) has some growing pains to overcome. But for a first-gen manifestation, it's a fairly polished piece.
If you're considering spending $3500 on a new monitor, then you probably already understand this display's requirements. 3D performance aside, you need a graphics card that can output to 3840x2160 using DisplayPort 1.2 or a pair of HDMI interfaces. You're also going to want the latest drivers for your Nvidia or AMD graphics card with support for DisplayID 1.3. Otherwise, configuring this display can be a bit of a pain. Fortunately, our test platform worked just fine with Nvidia's most recent software and a GeForce GTX Titan.
While we applaud Asus for giving enthusiasts a way to connect the PQ321Q via HDMI, driving each 1920x2160 tile independently, it's a far less elegant solution. If you have GPUs fast enough to make gaming at Ultra HD viable, then you probably have DisplayPort 1.2 support built-in already. Believe us, you don't want to spend money on a 4K screen only to run it at 30 Hz. It won’t flicker like the under-driven CRTs of old, but just moving your mouse cursor around on the Windows desktop is a choppy experience.
You'll notice that I didn't cover gaming performance in this review. Fortunately our esteemed editorial director covered that subject thoroughly in Gaming At 3840x2160: Is Your PC Ready For A 4K Display? back in September. His conclusion was that you need quite a bit of graphics horsepower to even approach 60 FPS in fast-paced titles like BioShock Infinite and Battlefield 3. And remember, in that test, an pair of GeForce GTX Titans in SLI only managed 38 FPS or so.

In the end, you need to consider what you want a resolution of 3840x2160 for. No matter the answer, you need a deep wallet. But if your desire is gaming specifically, plan on buying at least one $500 or higher graphics card, in addition to the PQ321Q's $3500 price. Why not just grab one of the cheap 4K TVs everyone is talking about? They're inexpensive for a reason; you don't get Ultra HD resolution at 60 Hz, and must instead drop to 30. Upconverting lower-resolution signals works fine for video content, but 30 Hz, personally, is a big problem for gaming or even using the Windows desktop.
For photographers and graphics professionals, this monitor is more than a shiny new toy. It has the accuracy to match other pro monitors and only lacks the Adobe RGB 1998 gamut to make it an ideal anchor for a photo editing workstation. With its pixel density of 140 ppi, there is nothing else in this screen size that can display an image with greater clarity and smooth-toned loveliness. Since the death of the CRT, we’ve had only fixed-pixel displays and the constant battle to eliminate visible dot structure. Asus' PQ321Q gets us to a point where we cross that threshold, yielding a film-like on-screen image.
If you're shopping for the most formidable-looking monitor available, that's Asus' PQ321Q with its imposing size and amazing resolution. You'll spend a fair amount of money in the process, but all of your friends are guaranteed to be envious. Make no mistake; this is a luxury item that demands a potent complementary graphics subsystem. There are some idiosyncrasies associated with the two tiled 1920x2160 panels, which may compel some enthusiasts to wait until later this year for single-scaler monitors. But practically, there should be little difference between those screens and the PQ321Q.
Your number of Ultra HD-capable options will multiply in 2014, and we want you to know what you're getting into before you buy. Asus' PQ321Q isn't new, but it remains in the top tier of monitors able to display 3840x2160 at 60 Hz. A crop of TN-based panels were announced at CES for sub-$1000 prices, and as those become available to test, you can bet we'll review them. Just bear in mind that vendors changing display technology and maximum refresh rate alter the 4K experience significantly. For now, this is as good as 4K gets.







