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October 9, 2010

Playoff Prospectus

The Mystery of the Inside Pitch

by Colin Wyers

Regardless of what team they follow, what league they favor, baseball fans seem to be united by one common cause: they all seem to think that umpires don’t know how to call balls and strikes. That would be problematic, of course, seeing as how often umpires are called upon to do that and how important it is to the game of baseball.

The latest cause for outrage was a pitch Lance Berkman took for a ball, which he would then follow up with a double on Thursday night in the Yankees' victory over the Twins in Game Two of the American League Division Series. Twins manager Ron Gardenhire got thrown out of the game for arguing the call of that pitch. And throwing fuel on the fire is TBS’s graphical display of pitch locations:

Screencaps of Lance Berkman's at-bat.

That animation in the lower right-hand corner of the screen is PitchTrax—different broadcasters come up with different names for it, but it’s all a nice graphical display of the same PITCHf/x data powering Gameday. And according to PitchTrax, that pitch caught just enough of the strike zone to be called a strike.

Did it?

Let’s put on our deerstalker caps and Inverness capes and play a game of “What did they know and when did they know it?”

And let’s start things off a little close to home.

What did you know and when did you know it?

What fans at home have to go off when judging balls and strikes is primarily the view provided by the center-field camera.  (We’ll discuss PITCHf/x in its various forms later on.)

There are a lot of things conspiring against you being able to judge balls and strikes off of video. You can sum it up broadly like this—your brain is a magnificent thing, and it takes the two-dimensional images you’re seeing on your television and reconstructs it so that you think you’re seeing it in three dimensions. It’s a marvelous process, and if you stop to think about it, it’s pretty amazing.

What it is not, however, is perfect.

In order to present the view that you see, the camera is positioned in the outfield at an offset, and then zoomed in to magnify the picture. This is, in essence, an act of deception—you are made to feel like you’re watching a little ways from behind the pitcher’s mound, when in reality you’re watching from the outfield bleachers.

And what the offset does is it distorts the view of the strike zone you have—it’s the phenomenon of parallax. You can observe this yourself, if you just go out to your car and check the gas gauge from the passenger’s seat and then from the driver’s seat:

Illustration of parallax using a car's gas gauge.

You also have problems with depth perception—essentially your brain is “guessing” the depth based upon visual cues in the image. This is difficult enough under the best of circumstances—there are really, really good reasons human beings have two eyes instead of one. Cyclops would be a terrible baseball player. You can get some idea of how this works just by covering one eye and trying to judge distance, then doing it with both eyes open.

The camera offset works against us here as well—it distorts our perception of the distances between the pitcher and the plate, for instance, as well as how we perceive the break of the pitch.

But the act of zooming the lens in has some consequences here as well. The most obvious effect of increasing the focal length of a lens is to increase the magnification and reduce the angle of view—you get a “closer” look. But that’s not the only effect. As you zoom in, lenses will tend to magnify more distant objects more than closer objects, like so:

Two cones at different levels of zoom, from a distance.

Now a different angle on the cones:

A top view of the same cones.

By zooming in on the cones, we make them seem to be closer to each other than they are. The same is true of the pitcher and the batter (and thus the pitch as it travels between them).

The act of recording a pitch on video significantly changes how it looks compared to how it really is. This is why if you’re watching on TV, and the umpire calls a close pitch in a way you disagree with, it is far more likely that the umpire is right than you.

(And of course, the exact offset and the amount of magnification changes from park to park and sometimes batter to batter. Some camera setups are going to make it look like more pitches are inside than they really are, others may make it look like pitches are lower than they are, and so on.)

What did Ron Gardenhire know?

I’m guessing not much. MLB dugouts are not well-positioned to give you a good view of the strike zone. After getting tossed, he could have gone into the video room and seen… the same video the rest of us saw. I doubt it does anything more for him than it does anyone else.

What did PITCHf/x know?

Of course, now we have PITCHf/x data (and before that, Questec). These systems use special cameras positioned in the stadium to record every pitch, and from there use computers to extract an estimated path of each pitch.

Now, we’ve already talked about the problems with using cameras to track pitches—but assuming you have good data on where the cameras were located relative to the field and the optical qualities of the lenses being used, using some advanced math you can get to a pretty accurate reconing of the pitched ball. Sportvision, makers of PITCHf/x, report that a properly calibrated PITCHf/x system is accurate to within a half an inch at the front of home plate.

But is the data we’re seeing coming from a properly calibrated system? Remember—the accuracy of the system is based on having accurate data on the location of the cameras and the properties of the lenses. In order to do this, PITCHf/x operators calibrate the cameras based on a set of landmarks placed upon the field before the start of the game. The key here is “before the start of the game.”

The game in question, for instance, had an announced attendance of 42,035—that’s a tickets sold count, not a turnstile count, but for a playoff game I imagine they’re pretty close. The average adult weighs something like 175 pounds (at least, that’s what they claim). What this means is that between the time the PITCHf/x system was calibrated and the time the first pitch was thrown, roughly 3,680 tons of baseball fan was introduced into Target Field, not counting seat cushions, signs and rally towels. And each one of those baseball fans was somewhere around 98.6 degrees Farenheit and radiating heat. All that weight and heat causes the stadium to actually move, and the cameras move with it.

In this case, I asked Mike Fast to look at the data and come up with an estimate of how far out of alignment the cameras at Target Field might have been that night. Estimating the error is difficult—in smaller samples, you have to contend with noise; in larger samples, you may miss changes that happen out of time.

PITCHf/x reported the pitch at .67 feet away from the center of home plate as it crossed the front of the plate; according to Mike’s corrections, it was probably .72 feet away, with a margin of error of .06 feet (accounting for the random error in pitch location measurement, plus the estimated error in the correction.) The edge of the zone (in other words, the edge of the plate) extends to .71 feet from the center of the plate in either direction. Now, PITCHf/x is giving us the center of the ball—if any part of the ball catches the plate, it’s a strike. So the effective zone extends to roughly .83 feet from the center of the plate.

So we think that pitch was probably a strike, given what we’ve seen with PITCHf/x—but we’re not entirely certain. (Remember, standard error means a 68 percent chance outcomes occur within the MOE.) It is, essentially, a borderline pitch.

And it is far easier for us to judge the accuracy of PITCHf/x’s estimate of the horizontal strike zone than the vertical—the position and width of home plate is fixed. The top and bottom of the strike zone moves with each batter, and if a batter shifts his stance, the top and bottom of the zone move as well. PITCHf/x operators manually record the strike zone (defined at the belt for the top and at the hollow of the knee) at the start of each at-bat; of course the batter is free to move around in the meantime. So when using the F/X data to judge whether or not a pitch is in the zone, you need to account not only for measurement error in the pitched ball, but the operator’s estimate of the strike zone as well.

This is why it is expressly unhelpful to go to your favorite PITCHf/x website, pull up a scatterplot from a single game, and use it as evidence the umpire did a bad job. The responsible thing to do (and this is what MLB does when using PITCHf/x to grade umpires) is to correct for these calibration errors and to look at a larger sample of data.

This is also one reason it’s infeasible right now to use PITCHf/x to call balls and strikes in a live game. (There are others—timeliness is one, of course. Another is operator error—game scorers are just as human as umpires, and they sometimes make mistakes in associating the PITCHf/x data with the right pitch in the game, for instance.)

What did the batter know?

I do want to make one last note—Hunter Wendelstedt isn’t the only person who thought the pitch was a ball. Berkman probably did as well, otherwise he would probably have swung at it.

What’s interesting to note here is that Berkman and Wendelstedt were the two people (besides possibly the catcher) with the best view of where the pitch crossed the plate. They’re also two people that have been selected for their ability to judge balls and strikes.

(An interesting side question—if a batter and an umpire disagree on a close pitch, which is more likely to be correct? I don’t know the answer to this. I mean, I’ve seen how Milton Bradley reacts on a called strike three, so I know how he feels about the answer. And he may even be right, in the case of Milton Bradley. But in general—I don’t know. I think it’s interesting, though.)

So I don’t think we’ll ever know, for sure, if that was “really” a ball or a strike. But in order to play a baseball game, you need to know the answer to that question—and Wendelstedt is the man entrusted to provide that answer. As Christina Kahrl so aptly put it, human umpires are the worst ways to determine if a pitch is a ball or a strike, except for the alternatives.

Colin Wyers is an author of Baseball Prospectus. 
Click here to see Colin's other articles. You can contact Colin by clicking here

24 comments have been left for this article. (Click to hide comments)

BP Comment Quick Links

awayish

meh, the 1st pitch was still 10 foot outside.

Oct 08, 2010 14:02 PM
rating: 0
 
BP staff member Chase Gharrity
BP staff

Excellent stuff, as per usual.

Oct 08, 2010 14:14 PM
 
bozarowski

That was an absolutely fascinating read - great stuff.

Oct 08, 2010 14:26 PM
rating: 6
 
Matt Kory

I'm not so sure that Berkman swings if he thinks its a strike. Sometimes as a hitter you "can't" swing, and yes this happens all the time to professional hitters. If he was looking fastball and Pavano throws a good change up his weight is going to be all on his front foot. I'm not saying that happened, just giving an example of why he might not have swung besides he knew it wasn't a strike.

Plus, if it was as close as you say it was (and looked to me like it was), I don't think Berkman can safely assume it won't be called a strike. The best reaction to a pitch that close with two strikes is to swing at it either in attempt to put it in play or in attempt to foul it off.

That said, great article.

Oct 08, 2010 14:27 PM
rating: 4
 
Brandon R. Warne

Great post Matty. I was going to ask the same thing, because if what was posted in the article were exactly true, we'd never have called third strikes.

Nonetheless, I'm still absolutely wowed by this article. Great stuff Colin.

Oct 09, 2010 08:47 AM
rating: 0
 
BP staff member Christina Kahrl
BP staff
(11)

Just offering an amen to the compliments, this was fun and informative.

Oct 08, 2010 14:36 PM
 
BP staff member Ben Lindbergh
BP staff

Ditto.

Oct 08, 2010 14:55 PM
 
BillJohnson

Agree with all the compliments, but I'd like to know more -- MUCH more -- about these "corrections" that Mike Fast calculated. Is a summary possible in print, or at least a link to somewhere where the methodology is described? Professional interest here as well as baseball-fan interest.

This said, it looks to me as if that pitch should have caught about an inch of plate, based on the center of the Fast model, and *some* plate even at the outer boundary of that model. A pitch that catches an inch of plate should be well within the power of a major-league ump to call correctly.

Oct 08, 2010 15:09 PM
rating: 1
 
Mike Fast

Bill, I've not published my method. However, the basic idea is that I compare a pitcher's pitch locations from one park to another. I do this for all the pitchers in the league for every game, and calculate the average shift.

For a single game, the error in the method is about +/- 0.10 feet. With more games in the sample, the error goes down. In this specific case, it looks like the PITCHf/x calibration at Target Field shifted between the September 21 and 22 games, giving us seven games of data to calculate the current plate location offset for the system. A seven-game sample gives an error of about +/- 0.04 feet.

Oct 08, 2010 19:43 PM
rating: 0
 
Randy Brown
(189)

I really think that for Colin's first article at BP, I should have been offered the choice between taking a red pill or a blue pill.

Oct 08, 2010 15:28 PM
rating: 4
 
rweiler

I'm not convinced that this is really an argument against computer calling of balls and strikes. For one thing, even if the system isn't perfectly calibrated, it would presumably be more likely to call pitches consistently than a human umpire. Pretty much every player, pitchers and hitters alike, say that they don't care all that much if the umpire isn't calling a 'rule book' strike zone as much as they care that he calls a consistent strike zone. A second factor is that given a commitment to a computerized system, camera's could quite likely be positioned so that calibration errors are less likely to occur.

Oct 08, 2010 17:16 PM
rating: 3
 
Matt Kory

I couldn't agree with this more.

Oct 08, 2010 22:28 PM
rating: 0
 
Mike Fast

One of the particular inconsistencies with a PITCHf/x strike zone at this point is that a human operator is required to set the top and bottom of the zone from video. This human operator can be and has been badly off at times.

It's probably true that the camera calibrations for the left/right edges could also be improved, but that's not a trivial task, and it's much easier to accomplish post hoc, which does no good for calling strikes accurately during the game. If systematic problems could be identified and if these were amenable to correction ahead of time, the accuracy of the systems probably could be improved. Keeping 30 separate systems in good health, though, would be a big challenge.

Oct 09, 2010 06:10 AM
rating: 1
 
BurrRutledge

Nice article, Colin.

Two comments... 1) just where was that pitch in all likelihood? And 2) how accurate is a batter's judgement after all?

1) A clarification regarding the location of the ball. After accounting for Fast's PITCHf/x corrections, there's a 68% chance that the edge of the ball was over the plate by between half an inch to 1-5/16" when it crossed the front of the plate (0.6" to 1.33").

If my math is right (and you would know better than I would), then there's also a **95.4%** chance that the edge of the ball was somewhere between 2" over the plate to just an 1/8" off it (2.05" over to .12" off).

This seems to be more than a "borderline pitch," statistically speaking.

1a) As awayish notes above, there's <0.0001% chance that the first pitch caught the edge of the plate. That pitch was a ball.

2) As for the batter's ball/strike judgement, it is important to note that his decision is made long before the pitch was actually a ball or a strike.

According to FanGraphs, Berkman himself swung at pitches outside the zone 20.1% of the time this year. Are we to assume that those would have been called strikes if he'd left the bat on his shoulder?

Oct 08, 2010 17:23 PM
rating: 3
 
BP staff member Colin Wyers
BP staff

Your math is right, if this is a randomly selected pitch. It isn't, though - we picked this pitch because the Pitch F/X location and the umpire's call disagreed. That affects the error bars (at least the shape of them) - again, I am comfortable with saying this was probably a strike, given the data we have, but we don't have enough data to be certain about it.

As for the earlier pitch in the sequence - yes, according to Pitch F/X and the defined boundaries of the strike zone in the rulebook, that was a ball. Nobody reacted to that call, though. And I'm pretty sure the reason is because a pitch there is always called a strike. The strike zone as it exists in practice isn't entirely square, and doesn't extend all the way up to the letters. I know this irks people, but I've never seen a justification for the rulebook zone being intrinsically better (since both pitchers and hitters seem to know what the "unofficial" zone is).

As for the Fangraphs data - that's BIS pitch location data, charted off the same broadcast feeds the rest of us see. Given all that stuff about parallax and focal length I talked about, I don't expect that data to be any good. (And some cursory examination has turned up rather startling evidence of the sort of park bias we would expect to see, given what we know about camera placement.)

Oct 09, 2010 08:47 AM
 
Noel Steere
(965)

"Your math is right, if this is a randomly selected pitch. It isn't, though - we picked this pitch because the Pitch F/X location and the umpire's call disagreed. That affects the error bars (at least the shape of them)"

Can you explain this further, please? If you're deferring to the umpire's call to determine whether the pitch is a ball or a strike to begin with, it seems like the article becomes tautological. It would have been less interesting, but you could have saved a lot of words by simply writing "because Wendelstedt said so".

BTW, as mentioned above, Gardenhire spoke to Mauer before arguing, who had no parallax issues.

Oct 10, 2010 00:08 AM
rating: 1
 
NYYanks826

Colin, definitely one of the most interesting articles I've read on this site in the last several weeks, and there's many to choose from.

Just want to add that I work for STATS Inc., and I am heavily involved in their baseball pitch-charting operation. The FIRST thing that my boss told me when I came to work there was that I had to take the camera angle into account when looking at pitch location. There had been many an employee who had walked through those doors only to have their pitch-charting abilities put into question because all of their recorded pitch locations were a couple of inches off in either direction.

Oct 08, 2010 23:56 PM
rating: 0
 
Mike Fast

NYYanks826, I'm curious, what reference was used to identify that their recorded pitch locations were off?

Oct 09, 2010 06:04 AM
rating: 0
 
dianagram

Informative ... entertaining . . . what I come to BP for.

Oct 09, 2010 06:23 AM
rating: 0
 
rgbauer

Great article. I would think, though, that Gardenhire would have talked to Joe Mauer before going ballistic about the call.

Oct 09, 2010 08:41 AM
rating: 0
 
Behemoth

The other thing is that Berkman is working with the strike zone that is being called in that game. The fact that he took the pitch doesn't mean that it was objectively a ball, but that he thought that it would be called a ball (assuming that we're accepting that him taking the pitch means something). Perhaps if it had been a similar pitch on the outside, he would have felt that he had to swing.

Oct 09, 2010 14:08 PM
rating: 1
 
Tynan

What a fascinating article. Thank you BP for your continual dose of reason amidst the banal drumbeat of the national media...

Oct 09, 2010 15:02 PM
rating: 2
 
Noel Steere
(965)

An amusing apologia, but isn't the parallax effect for the umpire *more* extreme than the camera angle in center field?

Also, I'd be curious to see what pitches in a simlar area from that pitch were called by the HP umpire for that game. That would nullify any claims of decalibration.

Oct 09, 2010 23:52 PM
rating: 2
 
flyingdutchman

Great stuff, Colin.

Oct 11, 2010 09:56 AM
rating: 0
 
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