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Results: Gamma And ANSI Contrast Ratio

HP ZR2740w Versus Asus PB278Q: QHD 27" Monitors, Tested
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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 greater depth and pop. 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.

HP ZR2740w

The ZR2740w displays nearly perfect gamma tracking. Aside from a microscopic dip at 30 percent, and a slightly larger hump at 90 percent, it hugs the 2.2 mark very closely. The 90 percent measurement represents an output deficiency of less than 3 cd/m2; an invisible error. We measured the gamma at several brightness levels and achieved the same results regardless of the setting.

Asus PB278Q

The PB278Q also measures well in the gamma tracking test. The deviations seen in the chart are extremely minor, representing, at most, a five percent variation in light output. Like the HP, these errors are invisible to the naked eye.

The gamma value range shows the quality of tracking from zero to 100 percent. A flatter gamma trace is obviously more desirable. This chart shows the distance between the highest and lowest gamma values. A smaller number indicates better tracking from minimum black to maximum white.

Both panels finish mid-pack in this test, although they are quite a bit closer to the leaders than they are the bottom two monitors. None of the screens in our chart display more than a tiny error. So, for all intents and purposes, the HP and Asus panels are close to the best we’ve measured.

Beginning with the Auria EQ276W review, we’re expressing gamma error as a percent deviation from 2.2. This is the ideal value and will most closely match the mastered gamma of video, game, and business graphic content.

While the AOC I2757FH is still the leader with a perfect 2.2 gamma average, the HP and Asus monitors are less than one percent off the mark. You can see from the tracking charts above how slight the errors are. Essentially, both screens achieve perfection in this test.

ANSI Contrast Ratio

Another important measure of contrast is ANSI. To perform this test, a checkerboard pattern of sixteen 0 and 100 percent squares are measured. 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, which also 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.

Given the superb on/off contrast numbers posted by both of today’s monitors, it’s no surprise to see them take the ANSI contrast crown, too. The ViewSonic VX2770Smh and AOC I2757FH are both only FHD displays, making the Samsung the next-best QHD monitor. For HP and Asus to post nearly double its ANSI contrast measurement is pretty impressive. In real-world viewing, this translates to greater image depth and more visible detail at the both extremes of the brightness range.

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  • 0 Hide
    KOKing , May 16, 2013 10:24 PM
    I've had one of these HPs at work for a couple of months (replacing an early 24" 1920x1200 IPS), which I've set fairly low), but as this review says, it's not really necessary. I was a little disappointed that, possibly because of the aspect ratio change to 16:9, it doesn't _feel_ like a lot more screen real estate.
  • -8 Hide
    Immoral Medic , May 16, 2013 11:13 PM
    Add 120hz, THEN it's enthusiast level.
  • -2 Hide
    bit_user , May 16, 2013 11:18 PM
    Where are all the OLED monitors? They should be cheap and plentiful, by now!
  • 8 Hide
    cangelini , May 16, 2013 11:59 PM
    SIDDHARTH MISHRAUseless review, the uniformity on these screens is pathetic, tried three of each, the color temp difference across the screen is over 1000K. Toms has very poor reviewers, only prad.de and overclockers.ru do reliable screen reviews. And btw the U2713HM is regularly on sale for $500 or so, the ZR2740W is now an overpriced relic lacking even an OSD.

    Screen uniformity is covered on page eight, and low points on both screens are discussed.
  • 0 Hide
    flong777 , May 17, 2013 2:03 AM
    Am I right by saying that the Asus monitor has more accurate color and better grayscale performance.
  • 2 Hide
    Marcus52 , May 17, 2013 2:07 AM
    Surprised that the Asus has slightly better lag results, as one of the reasons for not having an OSD is to reduce lag, and it can make a big difference. Of course, how you measure lag can get different results, and I've seen much lower numbers for the ZR2740w:

    http://www.tftcentral.co.uk/reviews/hp_zr2740w_v2.htm

    tftcentral is showing the HP as having far less lag than the Asus panel.
  • 4 Hide
    ceberle , May 17, 2013 5:07 AM
    The Asus certainly calibrates better than the HP; mainly because it can be calibrated. The HP is slightly better out of the box for grayscale and its chromaticity is also a touch better. Both screens have identical color to the eye. Only the instruments can tell the difference.

    Christian
  • 5 Hide
    ceberle , May 17, 2013 5:12 AM
    Regarding the lag results: It's hard to compare numbers from one review to another when the testing methods are so different. With our high-speed camera procedure, the only fair comparison is between the monitors we've tested. I would defend our response test as definitive though. Actually watching the screen draw in slow motion leaves no room for interpretation. The lag test is also consistent since we use the same signal chain for every screen. There is never a change in video cards, drivers, peripherals or any other device that might affect the result.

    Christian
  • 3 Hide
    dgingeri , May 17, 2013 7:22 AM
    I have the HP ZR2740w, and have for over a year now. It's a great looking monitor, and it performas well by my standards, but suffers from a significant lack of both reliability and support. HP's support is massively fragmented. It took me over three hours on the phone to get to the department that actually handled the support for this monitor. (It is a "Commercial" monitor, not business or personal. It's splitting hairs mighty thin, but that's the way HP's support is separated out.) When I finally got through, they sent a tech with a replacement monitor the next day. However, it also has two major hardware issues that render it useless when they occur. Most of the first run monitors had the power supplies die within months. The second run monitors had a serious issue with the control boards. All of them have issues with the USB hub, but it least the monitor keeps working if you don't have the USB cable plugged in. As an owner of one, I would not, under any circumstances, recommend this monitor to anyone.

    HP: the perfect example of a company falling apart because it is both too big and too fragmented.
  • 0 Hide
    ubercake , May 17, 2013 8:42 AM
    Does anyone know how absolute input lag of the IPS monitors compares with that of higher end TN-panel monitors?
  • -1 Hide
    maxinexus , May 17, 2013 9:02 AM
    Who cares about 1440p...where are the 4k gee how long does it going to take!!!
  • 1 Hide
    sempifi99 , May 17, 2013 9:52 AM
    I have had this HP monitor for about 2 years now. It is a good and solid monitor. It turns on in a matter of seconds and the 12 ms response time is not a problem at all. Though I do wish it was a bit quicker, but you can not have everything at this price point. Also, there is software calibration to adjust the color output so the lack of monitor adjustment did not bother me at all.


    What I don't understand is the difference of input lag compared to other reviews. The Acer has been measured at 16.6 ms while the HP is an amazing 3.6 ms with a CRT being used as the zero set point. I am not sure the exact toms hardware testing methodology but it seems to synthetic, not representing real world performance.
  • 0 Hide
    ceberle , May 17, 2013 12:56 PM
    The testing procedure is explained in the review. We shoot video at 1000 fps of a black to white screen draw. Then we simply count the number of frames it takes for the white field to fill the screen. The input lag is measured the same way. The video shows the pattern generator's lights flashing when the signal is sent to the monitor. We count the frames between the flash and the full rendering of the pattern to arrive at the input lag measurement. We do this five times and average the results.
    -Christian
  • -1 Hide
    Nintendo Maniac 64 , May 17, 2013 1:35 PM
    So I guess I'm the only one interested in a monitor's upscaling quality? I mean, we don't always play the latest AAA games - I myself like to play some Touhou from time to time, but it's locked to a 640x480 window which is pretty tiny on a high-res display. That leaves you with fullscreen which puts you at the mercy of your monitor's and/or GPU's upscaling ability.
  • 0 Hide
    Anonymous , May 17, 2013 2:24 PM
    Hp when oh when are you going to make a 30 inch 2560 x 1600 led or oled display or better yet a 4K ready version at 30 inches or better??
  • 1 Hide
    Spooderman , May 17, 2013 5:17 PM
    Considering the cost of such a panel, probably not for the next 5 or so years.
    soldier2013Hp when oh when are you going to make a 30 inch 2560 x 1600 led or oled display or better yet a 4K ready version at 30 inches or better??

  • 0 Hide
    mczak1 , May 17, 2013 8:43 PM
    No workaround for other resolutions? Seriously? Last time I checked gpus had output scalers (since about 15 years or so...). Maybe you need to activate it manually if the driver can't figure out the monitor can do scaling on its own but pretty sure it should work...
  • 1 Hide
    agnickolov , May 17, 2013 10:54 PM
    Quote:
    With UHD (Ultra HD, 4K, or 2160p) just around the corner, QHD represents the highest pixel count that you can put on your desktop right now.

    Technically, there's also 2880x1800, but it's only on iMac-s so far. Still, the panels exist...
  • 0 Hide
    MasterMace , May 17, 2013 11:46 PM
    1440 and 1600p are now old. 2160p is where it's at :) 
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