We’ve started to see the Moving Picture Response Time (MRPT) spec used more and more in recent times when marketing monitors, and it has reached a stage where we feel it may start to mislead consumers if it is not properly understood. In some cases, it’s even being abused by manufacturers and buyers should be aware of situations where it is used falsely as well.
What is MPRT Spec Measuring?
MPRT is all about articulating the level of perceived blur the user will experience from a given display. Traditional panel specs consider important things like the speed of the panel pixels (the G2G “response time”) and the frame “refresh rate” used. When considering MPRT specs, this also importantly accounts for eye movement and tracking of moving content on a sample-and-hold display technology like LCD. We talked about this in more detail in our article about blur reduction backlights but it’s important to understand how the human eye perceives motion blur on an LCD display.
What impacts a MPRT?
For a normal LCD display, without any special backlight technology added to specifically reduce perceived motion blur, the determining factor for MPRT is really the refresh rate. Pixel response times if they are particularly slow might add a small amount of additional time to a MPRT response time spec, but they are generally influenced almost entirely by the active refresh rate. On a 60Hz display the MPRT would be 16.67ms (i.e the speed at which a new frame is sent to the screen being 1000ms / 60Hz = 16.67ms). On a 120Hz display this is halved to 8.33ms. On a 144Hz it would be 6.94ms, and on a 240Hz display it would be 4.16ms. That’s the current limit of available LCD screens right now, and so a 4.16ms MPRT is really the minimum that could be achieved without additional measures being taken. So where do these super-low “1ms MPRT” specs come from?…
Factoring in Blur Reduction Backlights
The common MPRT spec you will see used by display manufacturers today is 1ms. To achieve a 1ms MPRT spec an LCD based on current technology needs to feature some kind of blur reduction backlight to make it possible. This is used to remove the perceived image persistence and blurring you experience on a sample-and-hold display like this by strobing the backlight on and off. This makes tracking of moving objects much easier, producing clearer and sharper images with noticeably less blurring. You can read our full article for a lot more information and testing of these kind of backlights. Without a blur reduction backlight you would need 1000fps, at 1000Hz and with reliable 1ms pixel response times, to achieve a real 1ms MPRT on an LCD display, which is right now not possible of course.
You will often see this 1ms MPRT spec used on screens featuring those kind of backlights which should in theory be a good indication that a blur reduction backlight is offered. That isn’t always the case though sadly as we’ve started to see this spec used spuriously by manufacturers on screens which don’t even feature a strobing blur reduction backlight!
As another note, just because a screen might use a blur reduction backlight, it doesn’t automatically mean that a 1ms MPRT would be realistic, as it will depend on various factors such as the strobe timing, strobe length, refresh rate etc. It should generally offer a better MPRT experience than a screen without a strobed backlight, but it’s not always truly 1ms. Although the spec seems to have crept in to modern display marketing as a generic catch-all for a screen which has a blur reduction backlight, regardless of whether that 1ms is actually fully achieved. The point here though is that where very low “MPRT” specs are quoted, that is normally an indication of a blur reduction backlight being available at least.
The issue with only quoting MPRT for response time
While a 1ms MPRT spec might be used so a manufacturer can advertise their screen to consumers with the “1ms” figure, it’s not always clear how the screen would perform without that feature enabled. For many situations, including when using VRR for G-sync/FreeSync, you can’t even use these blur reduction backlights. The performance without the strobing backlight in use needs to be considered carefully. More often than not the traditional “G2G” panel response time spec is probably more useful to understand, and at least gives you some kind of comparison to the way LCD screens are marketed the rest of the time. It’s very hard to consider how two screens compare when one has a blur reduction backlight and carries only a 1ms MPRT spec, and the other doesn’t offer that technology but instead has a 4ms G2G response time spec for example.
If MPRT specs are going to be included by manufacturers we would rather they also continue to provide the more traditional “G2G” response time spec as well to give a fairer comparison of the screen against other models which don’t feature blur reduction backlights. We know that those G2G response times figures are somewhat questionable in the real world anyway, but it’s better to provide some level of comparison between different screens without muddying the waters with an often meaningless MPRT spec.
As an example of why this spec is a problem on it’s own, you could have a very slow VA panel for instance that in normal use or VRR gaming offers a blurry experience and doesn’t perform well. If you added a strobing blur reduction backlight to it, maybe it could achieve a very fast, maybe even 1ms MPRT response time. On the other hand you could have a fast TN Film gaming screen without a blur reduction backlight that reliably achieves 2ms G2G response times, and therefore would be much better for normal gaming and VRR experience. Having a 1ms MPRT spec (or similar) just because a blur reduction backlight is used doesn’t tell the whole story at all.
Abuse of the 1ms MPRT Spec
In recent times we have started to see the odd example of displays being advertised with this 1ms MPRT spec, when in reality they don’t appear to even feature a strobing blur reduction backlight. We’ve seen the spec used on the recently announced AOC AGON AG353UCG, which (certainly from the pre-release sample we had chance to play with) didn’t seem to have a blur reduction mode available in the OSD menu. It’s possible that it could be added before final production starts so we will wait to see on that one. This is an area to keep an eye on we think.
As we’ve talked about above, there are challenges in quoting this spec at 1ms even if a strobing backlight is used. There are issues in only providing a MPRT spec when trying to consider a screen’s performance outside of that strobing backlight environment. But at least those displays have a blur reduction backlight to make the MPRT spec achievable, if not fully, then to some degree. Using the 1ms MPRT spec without having a strobing blur reduction backlight available is just misleading and unrealistic and should really stop. We will certainly criticize a display if blatant misleading specs are being used. It’s not achievable without a 1000fps / 1000Hz / 1ms G2G display if you aren’t using a strobing backlight, so we’re really not sure what manufacturers are trying to base this on.
You may also find this article at Blurbusters.com interesting for more information about MPRT and blurring in general.