4 ms·
As someone with long industry experience, I share your disbelief. I'd need to see the Fitts tests results for 250ms max delay (<150ms median?) on button state,
by kurthr 2y ago
As someone with long industry experience, I share your disbelief. I'd need to see the Fitts tests results for 250ms max delay (<150ms median?) on button state, as long press is also a thing. On touch/trackpads typical double tap rate is 4-5Hz and maximum tap rate is about 10-15Hz, achievable by relatively few. It's notable that you're dealing with a touchscreen here and not a mouse (people are faster at that).
Most premium Android phones in 2016 were 120-30ms motion-photon response time (low to midrange probably hit 250), while iPhones were ~80ms. Haptics add another ~30ms delay. There have been massive improvements since 2016, as it has been a competitive metric, but even with >120Hz screens sub 60ms max true latency is uncommon.
As (actually my long term memory of) the MS video shows faster refresh and lower latency greatly improve smoothness and are useful for moving objects, especially scrolling (though tearing is a real issue). The problem is much more pronounced in VR/MR as eye tracking of diagonal motion is VERY discriminating. That's why they shoot for >240Hz refresh rates. Over 1kHz there doesn't seem to be a lot of improvement (2ms latency) due to a combination of cone/rod/neural filtering.
If you want a very generic worst case latency calculation based on the touch acquisition rate and display refresh rate assuming no position calculation delay it is:
Latency = 2/Ftouch + 2/Fdispl = 2/16Hz + 2/16Hz = 250ms
- mrob 2y agoComparing latency with maximum tap rate is the same kind of fallacy as comparing it with reaction time.
- kurthr 2y ago"It practically guarantees people will think it's not working and tap again" Please provide a link to your data and analysis. Seriously, I hope you don't work for a major touchscreen supplier. A good UI can deal with relatively high latency input, a bad UI can make any latency unusable. Finger motion before/after contact and rapid high force contact bounces are common problems. Many high performance interfaces "gracefully" degrade report latency to similar levels under high interference conditions.
- mrob 2y ago"People" says nothing about how common it will be, only that it will happen. It's happened to me and I'm confident I'm not the only one.
- kurthr 2y agoThere is something called a FAR/FRR (False Accept Ratio)/(False Reject Ratio) where parameters on a UI system are tuned to optimize accurate interpretation of user intent (or user identification) for a given environment and action. Limiting response rate (eg debounce) to 2-3x the report rate is a common parameter change. There are always outliers in both user intent and experience, but a typical setting of <1% false reject and 1-100ppm false accept rate is achievable and usually acceptable. I'd also note that under video review people are notoriously bad at actually knowing how they interact with a touchscreen. Interestingly, fast response rates (and tactile response) reduce user complaints about proper operation even when UI errors remain constant. The users often assume they made the error rather than the machine. There are also interesting cognitive load effects.