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dwelltime |
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AgentHEX
Gold Member Joined: 12/14/2004 Location: Yo Mama Status: Offline Points: 1641 |
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Baal
Forum Moderator Joined: 01/21/2010 Location: unknown Status: Offline Points: 14335 |
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AgentHEX, I have repeatedly maintained on this thread and elsewhere
that the nervous system cannot possibly measure the actual dwell time directly--the
length of time the ball is still in contact with the surface based on
the images taken with a pretty fast camera. Sensory physiology is actually what I do for a living. I also know that different blades feel
different, and a lot of people describe setups as having a feel that
seems like "dwell". I have been playing table tennis seriously since I was ten years old and I do a lot of coaching. You may not believe that people can sense this. However, you state, and I believe you, that you can switch from LP to inverted on your BH with no change in level in an hour. So I simply wouldn't expect you to have developed that feel because I know exactly what that claim means. I suspect experienced players can do this reproducibly, but I know for a fact, however, that they cannot be detecting actual dwell given the ball is in contact with blade for substantially less than 7 ms (and I know what conduction velocities and synaptic delays are).
So what is this feeling? Earlier, you came close to my position by
saying it is a "psychological concept". You then went on to say there is no way of knowing if different people mean the same thing when they talk about dwell. Actually, in spite of the fact that you enjoy being an a$$ho1e about pretty much everything, you have hit right there on the key question -- is there some reproducibility to what people are actually sensing when they talk about dwell? My guess is that there is and that the sense of dwell may related to the duration of vibrations of all frequencies that move down the handle where they can be detected by neurons in the skin of the hand and fingers. Maybe blades like some softer feeling Btfly ALC blades vibrate less at high frequencies, but the totality of the vibrations may actually have longer duration, and so maybe people would say this kind of blade had a longer dwell. Other blades may have more vibration at high frequencies and you would feel more of a buzz, but maybe for less time. There is nothing intrinsically implausible about this. Of course there are no data either, so I could be wrong but it would be really interesting to know. The difference in our position is that you immediately assume that it is all nonsense, that everyone is full of it, and that you are a superior entity and that experienced players are just talking about stuff for the sake of talking about stuff. I assume that people actually have the touch to make quite subtle distinctions.
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AgentHEX
Gold Member Joined: 12/14/2004 Location: Yo Mama Status: Offline Points: 1641 |
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I believe people can sense a lot of things, just not necessarily what they claim to sense.
What do "conduction velocities and synaptic delays" have to do with measuring a duration of time? I don't know jack about sensory physiology, but if they mean what they sound like, that statement isn't obvious.
Probably. Just because there's no standard and therefore potentially arbitrary doesn't mean it's random. Though I'm more curious here why you think being an ass and being purposefully correct are mutually exclusive. Certainly this shouldn't be novel to a man of science.
Not sure if you're trying to be an ass by repeating more or less what I already said back to me, but I suppose I have no choice but to agree.
The question beckons, why would you still attribute wisdom to yourself and foolishness to myself given it's more reasonable that history repeats itself? I mean, is your mental representation of me as dumb as that straw man? |
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Baal
Forum Moderator Joined: 01/21/2010 Location: unknown Status: Offline Points: 14335 |
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...repeating more or less what I already said back to me
Read earlier thread started by Anton. I wrote about vibrations and sense of dwell months ago. I annoyed tt4me by bringing it up again in this thread. He probably has a point. What do "conduction velocities and synaptic delays" have to do with measuring a duration of time? Conduction velocities are synaptic delays are the reason why someone would not possibly be able to measure dwell time in time to make use of the information on that shot. Actually, more importantly, the response times of sensory receptors in skin would not respond to a 1-5 ms duration stimulus, which I didn't mention. Why would you still attribute wisdom to yourself and foolishness to myself My wisdom is limited. I did not claim anything more than a theory here about what people are feeling when they report dwell. You obviously know a lot about physics and engineering. You berate people on practically every thread you enter. Your claim to be able to play at the same level with LP and inverted with an adjustment time in hours is not something I would ever dispute, in fact I am quite sure it is true, but it is also very revealing. |
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tt4me
Gold Member Joined: 01/17/2013 Location: RC Poverty Zone Status: Offline Points: 1019 |
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i warned you guys. This is ridiculous. Another thread ruined just like Anton's.
Yes, you sure have. It is mostly your fault because you do not address the OP's original equation. In the future why don't you just post a link to what you have said before. That way we don't need to read it over and over again and you will save a lot of time REPEATING YOUR SELF and arguing with others. The only part of Baal's distraction that would been useful is if tell us what the minimum difference in real dwell time we could detect. Even a range of differences would be useful. I laugh when I see most people talk about dwell time. Yes, it is what they feel but it isn't what is really happening. I know they have NO clue. I would not bother to post anything intelligent on this thread now because people would get bored before getting here with all the off topic bickering in the previous 60+ posts. |
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Baal
Forum Moderator Joined: 01/21/2010 Location: unknown Status: Offline Points: 14335 |
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tt4me, you are probably right, except that I did answer the OP question in several posts-- less than 7 ms.
You are right, though, this is not very interesting anymore. Mea culpa. Note added later in defense: tt4me, I don't think i ruined Anton's thread because if you recall, the information I provided on this is exactly what he wanted to know, as he mentioned specifically in that thread. Don't forget, Anton (who we have no seen here in awhile) is in a graduate program in cognitive neuroscience. He thinks stuff like that is really interesting. I do too. Not everybody does. If you don't like my comments don't read them. But, because I don't want to unnecessarily piss you off, I will avoid this topic in the future. Peace. Edited by Baal - 08/29/2013 at 2:15pm |
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AgentHEX
Gold Member Joined: 12/14/2004 Location: Yo Mama Status: Offline Points: 1641 |
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That's fine, but why repeat some line I've said back to me as if it were novel and that I'm a fool for not considering it?
Sure, that's what seemed superficially obvious from their name but why bring them up when they're not relevant to the issue at hand, ie measuring duration?
Why not mention that the first time when it was pertinent? You're supposed to be the expert here so I'm confused why this discussion doesn't appear that way. By "proxy" of dwell it seems fairly straightforward that if there's a relationship (non-static across blades) between dwell and power of shot, and between that and various vibration characteristics, which seems entirely reasonable, then the player can pick up on any number of proxies for dwell by unconsciously sensing the first order derivative of such a relationship. For example, one blade can be "fast" (imply low dwell) meaning they are not only higher freq (ie hardness/elasticity), but both shorter vibration and lower magnitude of vibration. Then again, this is only one category of possibilities of what dwell can mean. For others the word seems synonymous with flex which perhaps refers to the lee-way before a blade enters non-linear elastic reaction. That's why I implied it's potentially arbitrary, yet not random. The linguistic question I posed is which of these is the real slim shady for each player who only know of "dwell" from context of the word in reviews and such with no external verification of what they're measuring or how to measure it? As you theorized yourself above, some of these proxies might be misleading if they're not consistent across blades, but again some might be rather more consistent. So with no way of even remotely aligning measurement standards across players, what can really be said about the affair? Don't conflate this with saying something about measuring blades in general, just how the completely clueless can speak intelligibly about "dwell". Again, you're the human expert here, but to me it seems a rather intractable issue. It's also worth mentioning since we're talking about proxies that I make the distinction because it's questionable whether the hand can measure dwell directly (like a camera does) anyway. What you feel on the hand is the reaction of the bat to the shot, and the questionable part is whether it even makes sense to talk about "feelling dwell" without that stuff in between, ergo the "feel" is the proxy.
I berate people on posing with introductory terms as much for their own future benefit as mine. One does not need to be any sort of expert here because it's blatantly obvious to anyone who paid attention in their intro classes. I'm often genuinely confused whether they're assuming everyone else present is ignorant or just don't know better themselves. Likewise if I ever do such a thing, let me know so I don't repeat the same embarrassment when it matters.
What is it revealing of? There's provably someone @~2200 who can switch between carbon+max inverted and clipboard w/ only ~100 loss in even shorter period of time. Does it imply I'm worse than them because it may take me longer? Or that my game is very stylistically advanced that it takes so long? I really don't know. Edited by AgentHEX - 08/29/2013 at 5:19pm |
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AgentHEX
Gold Member Joined: 12/14/2004 Location: Yo Mama Status: Offline Points: 1641 |
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Ok, my bad on assuming the posing since it seems everyone was instead assuming zeio can think clearly about basic physics in that former thread. Kind of odd someone can read so many studies and still be so terrible at it. I mean, conflating sample frequency with general timing just because the units match is something you only expect mercuur to do.
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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@ Baal: Man, I sent you a handshake, I thought you would reciprocate ... now I don't even have the time to fully express my resentment because AgentHex may pop up any second now...
Seriously, this thread interests me hugely - I feel that there is a high practical potential to the concept of dwelltime when determined strictly and reproducibly for different rackets. Yes, rackets, obviously, because the OP clearly had in mind a blade-rubber combo, and this is what plays in our hand, after all. I have a V1 with a thick Vega Europe on it and this has a huge dwell time - don't tell me it does not... I also have a 95 g Juic SBA with 1.9 Sriver on the backhand side, and the dwell there is much shorter, don't tell me it is not... although I know it is not that short either because I can sens the ball stay there for a little... Anything else - it would be nice to be able to attach a reliable dwelltime number to it in order to compare, please don't tell me it would be useless... I close my eyes and envision a 2020 catalogue offering tables of blade rubber combinations, right next to their dwelltime, for your convenience (and next to respective prices, for your desperation...) . Imagine a scenario when we actually found a really easy way to determine the said dwelltime. Someone here would quickly add a table of many numbers... I bet you we would suddenly start discussing how we relate our game to the various dwelltimes. Regarding wisdom and foolishness... that would belong to a thread in a different forum... but the way I see it - true wisdom is non-aggressive and tends to patiently probe reality because it knows how huge the unknown is and how small is the domain of what is known. And there is so much in between... I had a colleague in high school who had a clear and really very strong aversion to any strict knowledge, but he wrote passionately his literature assignments covering technology issues, sports and other areas of measurable human activity. He was disputing aggressively and making really prickly comments toward those who dared to challenge him, and yes, he offended people badly... Once I asked him what his motivation was.. he told me he wanted to be a journalist. Even though he had to repeat a grade or two, decades later I heard he actually became one... maybe that's it?
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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AgentHEX
Gold Member Joined: 12/14/2004 Location: Yo Mama Status: Offline Points: 1641 |
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No it really wouldn't. First a "dwelltime" in itself is pretty meaningless since it's at least contiguous function against ball speed (likely closely correlated to elasticity in blades) not necessarily reducible to a scalar. Second, even given better characterization, the product of rubber/blade combo isn't necessarily simple convolution esp if you'd want to do more than hit the ball straight on. There are further issues, but at this point I'm not sure how the less technically competent are even supposed to make sense of this in a marketing catalog.
True wisdom is exactly like the name says. Everything else is just practical considerations. For example, some folks simply have less patience for hand-holding than others, and many have a strong aversion to bruised ego. Generalizing from anecdotes is less useful when we know the direct causes. Edited by AgentHEX - 08/29/2013 at 8:10pm |
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Baal
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Sorry man. I needed to actually do the work I'm paid for. It's grant writing season, I'm looking into the brink, and sometimes for sanity I come here and post a bunch of nonsense before getting back to my Significance and my Innovation. Mechanosensitive channels. |
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JacekGM
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Super... can you selectively block these in bacteria vs in mammals ? Not that I want to dwell (time) on this topic here...
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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Baal
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Does anybody know if the wood they use for handles these days is pretty much all the same? For sure it didn't use to be! We worry a lot about the plys in the blade itself, but a lot of what we feel has to go through the handle, except for our forefinger on the surface (and for some people the side of the thumb). But we never talk about the wood on the handle and the manufacturers rarely say anything about that either.
Handle shape and size matters a lot to me. One of the many things that determines the sensitivity of vibration detectors in your skin is the pressure exerted on the surface (for example how hard you grip something). Changes in the handle shape is going to cause pressures to be exerted in slightly different parts of your hand, which take some getting used to. You would think that how hard the handle wood is might matter too. I am curious that there is not as much said about that. I have the impression that most people are not real crazy about excessively hollow handles, but when they first came out it was the next Big Thing. |
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igorponger
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http://protabletennis.net/book/export/html/89
Mr. Fullen is right indeed. There is no "absolute" dwell time. The time span that ball sits on the racket will vary distinctly from a stroke to a stroke. Smashing stroke, chopping and stop-blocking will produce different dwell time, and the difference is measured just by few millliseconds, from 0.001 to 0.004, if my memory still serving me. |
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haggisv
Forum Moderator Dark Knight Joined: 06/28/2005 Location: Australia Status: Offline Points: 5104 |
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It's simply another subjective term, just like 'throw', that's meaningless as an actual number, but useful for comparison to other equipment. If you don't like it or don't believe in it, ignore it, but personally I find it quite useful for comparison.
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AgentHEX
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Vibration modes is primarily function of bat materials (incl rubber) itself since shape is predetermined. Unless the handle is strange it shouldn't matter too much to main area the vibrations are created (in that if you just cut it off, the changes shouldn't be drastic) as long as there's solid connection to the hand. |
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AgentHEX
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The problem is that even if each individual can reliably feel what they call dwell, there's no reliable way to intelligibly communicate it to others accurately. It's also not quite akin to throw in since throw is more conceptually straightforward and easily verified. |
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stiltt
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At whatever level, a person who tests a lot of rubbers can make the difference between the dwell of one rubber and another; if that person shares the word "dwell" in his/her tt vocabulary with a reader, the latter will understand what the reviewer means: one rubber has more dwell than the other.
People who do not like the word "dwell' should propose something else; or they could sit in a meditative stance yelling "DWEEEEEEEEELLLLLLL" and the enlightenment will come. |
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haggisv
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I never said it needs to be accurate. Just the information from an experienced reviewer that the dwell time is high (obviously compared to other equipment they've tested) can be quite useful. Similarly the comparison that it's higher than something else (that I may have played with) can be very useful. If you try and put numbers to it, it does indeed too subjective to be useful.
I disagree... throw is also subjective as it depends on too many factors, like the stroke played, how hard you hit the ball, etc. This is why I think it's again mainly useful for comparison purposed, just like dwell. |
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AgentHEX
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I've already addressed this but will try to demonstrate using an analogy. A car is often described as "faster" than another, but this can mean any number of things including HP, torque, top speed, etc. These are all well understood correlated measures in an entangled but coherent mesh of relationships, yet describe different aspects of performance. Even using "faster", a more objective concept than "dwell" is rather perilous without careful definition least we consider an f1 car and salt racer both faster than the other. The difference here to TT is that the average player or even EJ simply lacks both the standardized vocabulary and technical sophistication to speak meaningfully of these measures or physical concepts such as acceleration, not unlike an auto enthusiast ignorant of the terms above trying to rate various cars. |
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AgentHEX
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If you ask ten people how they feel dwell, expect many different answers. If there's not even any sort of shared definable quality to a concept, what meaning is it supposed to represent? Compared this to throw below.
No, throw can be pretty well defined since it's hardly just a nebulous feeling. If a bat is held at same position (or other swung) against given incoming shot (eg robot), it will rebound the ball at a measurably objectively and repeatedly verifiable angle (and speed). |
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stiltt
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right or wrong, using the word "dwell", people exchange information; through trial and error they will eventually reach their goal (good for us) unlike a superior mind who will get it right away (good for him and you).
In your analogy if the people use the word "fast" because that's what interests them why should they be pointed at for not knowing about or ignoring torque and the 4-stroke cycle? IOW, why would anybody care? Would you engage with a bunch of teenagers loving their customized honda civic and tell them: "you don't get it; that huge muffler does nothing to you it only costs you money and it's also ugly; your hi-fi system is such an overkill for such a low interior volume and it does not even sound good". |
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stiltt
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if 10 people have slightly different definitions of dwell but can arrange 10 rubbers in the same order when comparing their dwell characteristics then the dwell is good a tool to communicate. |
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AgentHEX
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People can do whatever they want, I'm just pointing out in a thread about dwell that the usage of term is fraught with error. I've certainly benefited from thinking a bit about an aspect of a game that interests me, and maybe like minded individual did, too.
I've probably also pointed out similar follies in a thread about exhaust systems some ages ago. Maybe someone got upset then, too, but then again it's a bad idea to read the internet for those folks. |
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tt4me
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No it isn't!!!! One can get a high speed camera a count the frames the ball is in contact with the paddle. It is simple.
Dwell time would be meaningful IF everyone agreed it was the time the ball was in contact with the rubber. There must be some other medical term that covers what Baal is talking about. I am not disputing what he says. I just thing it is off topic. I am not a medical person so I don't know what the term would be for what Baal is talking about. I do know that other sports use dwell as the time that the ball is in contact with what ever they are hitting it with. I KNOW that dwell time can be roughly measured using a high speed camera. If one can do that math and analyze the video they can calculate what happens between the frames. I do agree that throw is a subjective term but useless term until someone defines throw with units. I see all sorts of ways throw gets used like throw distance, throw height or throw angle. In contrast, dwell time is easy to define. It is the time the ball is in contact with the paddle. I suggested earlier. One will not find the answer here. I think these guys can find an answer. http://www.youtube.com/watch?v=xe-f4gokRBs Edit, you guys are wasting your time and filling up Alex's disk with noise. Do you want answers or don't you? Edited by tt4me - 08/30/2013 at 3:05am |
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AgentHEX
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Or more likely people just subtly align their results with the prevailing popular opinion, which is even worse than arbitrarily varied measures in the first place where at least some useful info might exist. Just like reviews of TBS vs Viscaria, or '96 vs '97 Sonoma Merlot. I distinctly remember stock of P.Noir rising after Sideways not unlike Viscaria after ZJK. |
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AgentHEX
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Yet this has little to do with what people are referring to as "dwell". Recall this is confusing due to two words/concepts that happen to be spelled the same. You also don't need a high speed camera to measure dwell, just a reasonably accurate one. |
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igorponger
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AN IMPORTANTE DISCOVERY.
http://tt.tennis-warehouse.com/showpost.php?p=6986320&postcount=27 This is a statement of tremendous importance. This is to end any more disputes about the DW, once and for all. THIS scientific fact states clearly --- it is impossible for a human brain to percept/recognize HOW LONG the ball touches racket on impact. One can only sense the moment of time at which the ball hits racket, but one can never tell the moment the ball comes off the racket. Yes. Yes. Yes. Dwell Time can be measured well with high speed camera, still it is NONE perceptible by human body sensors, and therefore one can't make any practical use of this.. That is that. Great and interesting Discovery. Thanks to Mr. Pvaudio, a science versed forumer from the Tennis Talks. |
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AgentHEX
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You're making the common mistake of conflating reacting within a span of time vs. simply measuring a duration of time. Propagation speed of neutral signals has no direct bearing on the latter. It would help to read the thread before mouthing off because this was already mentioned.
Edited by AgentHEX - 08/30/2013 at 3:13am |
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tt4me
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The ball doesn't care about what people feel. The trajectory of the ball is not influenced by what people feel. Only what actually happens affects the ball.
Show me where dwell is a medical term used to describe how long a ball is in contact with the paddle.
An accelerometer would do if the sample rate is high enough. What else would you propose? Most are probably wondering WTF am I talking about. |
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