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Comment by yalue | Hacker News Reader

I understand that key travel time is included in the latency measurements to facilitate the camera-based measurement, but wouldn't it make more sense to measure latency purely in terms of electrical signals? For example, measuring the time between the first connection of the circuit in the keyswitch to the time at which the USB packet including the keypress is sent across the wire? This seems like it would be equally possible to test with a second logic analyzer, without relying on a high FPS camera. Many people who use "special" mechanical keyboards are well aware of the actuation points on their keyboards, and understand that there are tradeoffs between travel time, physical feedback, and so on.

Put another way, unless you think gently resting your fingerprints on the top of a key should count as a "press", then it doesn't make sense to include the key travel time in latency.

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Yeah I think so. Relevant quote from the article below. How are the keys being pressed, manually? We could have skipped all this by just knowing key travel time will govern based on his experiment. If you really want to know the fastest keyboards look at what the winners of typing competitions use.

>A major source of latency is key travel time. It’s not a coincidence that the quickest keyboard measured also has the shortest key travel distance by a large margin. The video setup I’m using to measure end-to-end latency is a 240 fps camera, which means that frames are 4ms apart. When videoing “normal" keypresses and typing, it takes 4-8 frames for a key to become fully depressed. Most switches will start firing before the key is fully depressed, but the key travel time is still significant and can easily add 10ms of delay (or more, depending on the switch mechanism). Contrast this to the Apple "magic" keyboard measured, where the key travel is so short that it can’t be captured with a 240 fps camera, indicating that the key travel time is < 4ms.

Yeah, this is a pretty big issue that disproportionately effects mechanical keyboards, failing to account for the fact that the "ready" position in the context of gaming on a mechanical keyboard likely involves having the key being slightly depressed, just above the actuation point (think resting your fingers on WASD).

The author is concerned about perception of latency. You perceive the time from when you make the decision to press a button to when you see the result. From this perspective mechanical vs electrical is irrelevant.

That's assuming that the user always starts from a completely uncompressed key. On a medium-weight mechanical keyboard, for latency-sensitive actions you'd likely be hovering the key just above its actuation point (one of the reasons I actually prefer tactile keys for gaming: the idea keyboard holds the weight of my resting fingers just above the actuation point).

The article responds to this:

> A common response to this is that "real" gamers will preload keys so that they don't have to pay the key travel cost, but if you go around with a high speed camera and look at how people actually use their keyboards, the fraction of keypresses that are significantly preloaded is basically zero even when you look at gamers. It's possible you'd see something different if you look at high-level competitive gamers, but even then, just for example, people who use a standard wasd or esdf layout will typically not preload a key when going from back to forward. Also, the idea that it's fine that keys have a bunch of useless travel because you can pre-depress the key before really pressing the key is just absurd. That's like saying latency on modern computers is fine because some people build gaming boxes that, when run with unusually well optimzed software, get 50ms response time. Normal, non-hardcore-gaming users simply aren't going to do this. Since that's the vast majority of the market, even if all "serious" gamers did this, that would stll be a round error.

That's the best case scenario, not average case scenario. It only regularly happens with gun/mouse in shooters, as in any games that have abilities to cast you don't exactly know which one you might cast next in a given moment.

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