Input Lag and Power Use

Since the HP automatically scales the image if it is not sent at 2560x1440 and I don’t have a CRT that can produce that resolution, the HP had to run at 1920x1080 resolution for the lag tests. This is our second review using the SMTT program to test lag, but this lets us separate the input lag from the pixel response time, so we can hopefully figure out the effect of scaling the image. There is a chance that the performance with a native 2560x1440 signal could be better on the input lag, so these measurements again represent the worst case scenario.

Processing Lag Comparison (By FPS)

Despite this, the lag on the HP is very low overall, with 14.55ms being the worst case scenario. This breaks down at 2.6ms of input lag, and then 11.95ms of pixel response time. This is less than a frame of lag at the 60Hz refresh rate the display supports, so it should be fast enough for your gaming use, though hopefully your video card can keep up with it at 2560x1440. The effective lag, which is a more subjective measurement, came in at right around 10ms in my estimation. At that point you can clearly see what color a pixel was changing to, even if it hasn’t reached peak brightness yet. I really don’t think anyone will have issues gaming on the HP, which is very nice.

With the size of the ZR2740w, and the amount of light that if can put out, you can imagine that even with an LED lighting system it is going to use a lot of power. At minimum brightness the HP consumed 26 watts, and at maximum brightness it consumed 96 watts. With my usual settings (closer to 150-160 nits of brightness) I was seeing closer to 45 watts of power use on it. This isn’t the most efficient display you can get, but when you consider that it is likely to replace dual 24” monitors for a lot of users, the power use is better in perspective. Compared to the 30” monitors we have reviewed it is very good, and about equal to the 27” Apple Cinema Display.

LCD Power Draw (Kill-A-Watt)

Brightness and Contrast Conclusion: Big Bang for the Buck


View All Comments

  • Snowshredder102 - Friday, March 16, 2012 - link

    These monitors have been floating around the $700 price range for some time now. Not a fan of a 16:9 monitor for that price, this monitor also has terrible response time for anyone that plays any games. I don't see anything really special about this. Reply
  • JarredWalton - Friday, March 16, 2012 - link

    Please define "terrible", because in my experience less than a frame of lag is nothing. I have an older S-PVA (Dell 2408WFP) with about three frames of lag. My personal threshold is around 20ms before it starts getting bad, relative to an S-IPS 30" display. Based on Chris' measurements I would guess I could get away with ~35ms delay relative to a CRT.

    As for your comment in regards to price, you're smoking something:

    $600 27" LCDs have been around for a long time, but they were all 1920x1080 or maybe 1920x1200. If you can provide links to any other 2560x1440 27" displays with IPS panels that cost less than $700, let's see them. I can't recall ever seeing anything like that for this price, outside of the HP ZR2740w.
  • Snowshredder102 - Friday, March 16, 2012 - link

    I've heard people claim that an input lag above 10 starts getting bad. As for the price you're looking at FULL retail. I've seen these monitors for sale on a number of places. My U3011 has an MSRP of $1500, I bought it for $1150 on sale and during that time the u2711 was at $750. I've seen brand new HP 2560x1440 IPS monitors for $650. Sales come by decently often, you just have to put some effort in scoping out deals. Reply
  • JarredWalton - Friday, March 16, 2012 - link

    A periodic sale is one thing, a normal price is another. The ZR2740w might go on periodic sales for under $550 given the current MSRP. It's good to see the base price well under $1000 for one of these displays for a change. Reply
  • esse09 - Friday, March 16, 2012 - link

    Hello Jarred,
    the U2711 retails for the same price as the ZR2740w.
    Based on your own reviews i'd say you should suggest picking the Dell monitor instead of this one as far as bang for the buck is concerned. What do you think?
  • JarredWalton - Friday, March 16, 2012 - link

    It depends what you're after, really. The U2711 currently goes for more like $830+ based on what I can find:

    That's a full $200 more than what we can find the ZR2740w selling for, and it's not all sunshine and roses for the U2711. It has excellent colors, more connectivity options... and more input lag/processing lag. Tom's Hardware measured lag at 98ms ( but I measured it at just 16-18ms ( I'm not sure which is "right", so I'll leave that to you.

    If you don't need the extra inputs or high color gamut, and you'd prefer to save $200, I'd take the HP. If you can get the Dell on sale for $630, however, I'd probably go that route.
  • Mitch89 - Sunday, March 18, 2012 - link

    I'm a big fan of the U2711, I've used two of them on a video editing suite I built and they are gorgeous. They are AU$899 here in Australia, and despite the fact they cost more here than the US (despite our dollar being higher...) they are easily worth the money. Reply
  • Ramiliez - Friday, March 16, 2012 - link

    Magical number for 60Hz panels is 16,7 ms

    Common monitor refresh rate is 60Hz that means every 16,7 ms image is refreshed therefore response time (crystal color change + input lag) below 16,7 ms is useless

    For 120Hz panels the magic number is 8,3 ms
  • mathew7 - Friday, March 16, 2012 - link

    Please don't confuse refresh rate and input lag.
    Input lag means the time for a pixel on the wire to be shown on screen. If a monitor waits for a whole image before refreshing it's panel, then yes, you will have 16ms input lag. But this will be for the top-left pixel. The bottom-right will be less, as the panel refresh nowadays is much faster than accepted refresh rate.

    And 0 input+processing lag is desireable for any fast-paced action. It's not useless, it's ideal. And don't forget also the rendering time.

    PS: your comparison is like saying that if your car's top speed is 100mph, then there is not reason for you to drive more than 100 miles.
  • imaheadcase - Friday, March 16, 2012 - link

    Input lag is only as bad as the person who uses the monitor notices.

    I have a U2410 24inch and don't notice a difference in gaming with it vs a 120hz monitor.

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