^I've been actively thinking (read: educating myself) about the above in recent days and weeks. It seems that there is indeed more to monitor responsiveness and smoothness of motion than just the refresh rate.
A 120Hz display refreshes every 8.33ms (compared to 16.67ms for 60Hz displays). This
does in itself provide benefits because the image is updated more frequently, it allows you to 'see' 120 (instead of just 60)fps in a gaming/rendering environment and, as I understand it, it also mitigates motion blur on sample and hold displays by updating pixels with a new frame in cases where they would otherwise linger with unwanted persistence.
On this latter point (motion blur), however, it seems necessary to talk about refresh rates in combination with response times. Mark Rehjon of Blur Blusters tells me that, in order to minimise motion blur cause by the pixel persistence of the panel (note: a
different beast to perceived motion blur caused by how our eyes track movement combined with the 'sample and hold' / continually-displayed refreshes of many LCDs) you ideally need a pixel response time that it
about half as long as the monitor's refresh time, or ideally lower.
In a 60Hz display, the image is refreshed every 16.67ms, so according to Mark's rule you need the pixel response time to be below about 8ms. Above that, and you get motion blur from pixel persistence (in
addition to perceived motion blur from sample and hold). Below this, and it's effectively a non-issue because the bulk of motion blur still perceived is due to sample and hold rather than anything to do with the panel. Pixel response times of 8ms and lower have been a done deal on many displays for some time, so no problems here.
However, on a display running at 120Hz, the image is refreshed every 8.33ms, which means that you ideally want the pixel response time to be below about 4ms in order to avoid motion blur from pixel persistence being an issue. The fastest (native, TN) 120Hz monitors do this, but as discussed above there are other 120Hz TN displays with not-so-fast pixel response times. On overclockable, non-TN displays (not to be named), most if not all colour/grey pixel transitions are likely to be above 4ms, and several of them are definitely a lot longer. This means that, while the higher refresh rate on this displays does provide certain advantages, the reduction in motion blur that usually comes with 120Hz is compromised slightly by pixel persistence.
Mark summed this all up on these very forums a while back, in
this post from February.
Voilà. So 120Hz monitors with response times above 4ms do have less motion blur than a typical 60Hz screen (in addition to the other benefits of 120Hz I mentioned at the start), but the reduction in motion blur is about 10% behind that of 120Hz monitors with very low response times.
To what extent does that 10% even matter? That's the impossible and subjective question. Some people are naturally more sensitive to motion blur than others. Folks who've been using CRTs competitively for shooters all these years are probably much more easily bugged by it than those of us who gave up CRTs a long time ago. I personally suspect that I am not that sensitive to it, though I have not yet experienced a LightBoost-enabled monitor with the zero motion blur hack....
Disclaimer: I'm not a technical expert and the above is more a 'stream of consciousness in progress' rather than authoritative information. For technically reliable information, please consult people like PCM2
