aiming

 Dr. Dave's answers to frequently-asked questions (FAQs),
mostly from the BD CCB and AZB discussion forums

maintained for the book: The Illustrated Principles of Pool and Billiards
and the monthly Billiards Digest "Illustrated Principles" instructional articles

for more information, see Section3.02 in The Illustrated Principles of Pool and Billiards

aiming "systems"

How do different people aim?

I don't use the aiming systems (the fractional system or Hal's system) presented in TP A.11. I just presented them to show that they are the same geometrically. I also presented an example to help clear up some of the debate that started earlier.

I personally use a combination of straight intuition (just "seeing the angle"), ghost ball aiming (see NV 3.1 and NV 3.2), and contact point visualization. Bottom line: I just visualize the aim without using any kind of fractional on fixed-reference compensation system. I certainly don't use any kind of math or numbers when I aim, like some people have suggested. I think my aim is usually very good; although, my execution isn't always perfect.

I think (but know) that if a scientific survey were done with all of the pro players, many (maybe even most) of them would say that aiming comes naturally (i.e., its "intuitive" or they just "see the angle"), because they have played so much. Some people might find the How the Pros Aim article interesting; although, it is not the result of a rigorous scientific study.

from Spiderman:
You are correct, that is a fine article. But, as even that author concludes, it will never be "put to rest". Luckily, it doesn't really matter. The numerous pros interviewed used a vast and disparate array of aiming techniques. "Ghost Ball" seemed to be the only somewhat-recurring assertion, but not to a dominant extent. There were even one or two who claimed to aim by "feel".

Personally I use the "ghost ball" technique most often, but not to exclusion of others. I learned to play with no coaching, and "ghost ball" was something I thought I invented . I didn't learn what everyone else called it until I read "99 Critical Shots". Now on some simple shots I just let the subconscious handle aiming - all I visualize is the desired result, and it happens, right down to how much the CB path distorts from the draw, and how far it rolls after the second rail. On very thin cuts I may visualize actual ball-to-ball contact points. But on ALL caroms I fall back to an augmented ghost-ball alignment. Most players will hit caroms too thick if they rely on feel.

What I would like to stress from that article is the one thing that everyone interviewed DID have in common - "the balls went in" for them.

The fact that so many different methods will work, and work well, ensures that some will die convinced that "their" way is "the only" way. Clearly all brains are not wired alike, and no one techinque is ever going to be a panacea. Use what works for you, as long as it makes sense.

from Bob_Jewett:
You may find one of the following articles useful. I included the article about finding the center of the pocket because if you don't know where that is, it's pretty hard to aim well.

http://www.sfbilliards.com/articles/1993-06.pdf -- close ball aiming

http://www.sfbilliards.com/articles/1996-02.pdf -- frozen ball aiming

http://www.sfbilliards.com/articles/1996-02.pdf -- finding the center of the pocket

http://www.sfbilliards.com/articles/1999-11.pdf -- a smorgasbord of systems

http://www.sfbilliards.com/articles/2000-06.pdf -- analysis of three systems

http://www.sfbilliards.com/articles/2004-06.pdf -- ferrule system, lights system, overlap system

http://www.sfbilliards.com/articles/2004-12.pdf -- aiming devices

http://www.sfbilliards.com/articles/2005-01.pdf -- some more devices

http://www.sfbilliards.com/articles/2005-06.pdf -- a history of parallel aiming [/quote]

aim compensation for squirt, swerve, and throw

Is there a style of play (e.g., using aim-and-pivot aiming methods) that can compensate for all of the effects of squirt, swerve, and throw?

There is no sliver-bullet "style of play" that can magically solve all of the "challenges" associate with compensating one's aim for squirt, throw, and swerve. The BHE and FHE aim-and-pivot methods (see my November '07 article) can be used to adjust for squirt (and in some cases the combination of squirt, swerve and/or throw), but swerve and throw vary too much with shot speed, shot distance, cue elevation, type and amount of English, amount of forward roll, ball and cloth conditions, etc.). I think the best you can do is be knowledgeable of all of the effects (e.g., see my March '08 article summarizing squirt and swerve effects and my June '07 article summarizing throw effects) and/or have solid intuition based on many years of successful practice and play. There is no magical "style of play" that can solve all of the world's problems. Pool is hard.

See also:

 

What squirt, swerve, and throw effects do I need to be aware of?

As many of you probably know, I have done lots of analysis and experiments over the years concerning squirt, swerve, and throw. Many illustrations, explanations, and examples can be found in my 2006 through 2008 BD articles available online.

Below is a quick summary of some of the useful pieces of information presented in the articles. Hopefully, some might find this list useful to validate many things you know already and/or to check if there are some effects you don't know about.

FYI, here's a short glossary of some of the terms used:

BHE: back-hand English
CB: cue ball
CIT: cut-induced throw
FHE: front-hand English
gearing OE: the amount of outside English that results in no throw
IE: inside English
OB: object ball
OE: outside English
SIT: spin-induced throw
squerve: combination of squirt and swerve

See my online glossary and articles for more details.

Squirt, Swerve, and Throw Effects:
(everything you ever wanted to know about squirt, swerve, and throw)

1. Squirt increases with the amount of English.
2. Squirt does not depend on shot speed.
3. Squirt increases with the amount of shaft end-mass (e.g., a low-squirt cue has less end-mass and results in less squirt).
4. Squirt is less with a heavier CB.
5. Squerve can be zero with certain speeds and cue elevations for a given shot distance, amount of English, and cue.
6. Squirt or squerve can be canceled using back-hand English (BHE) and/or front-hand English (FHE) aim-and-pivot methods (see my November '07 article).
7. Swerve increases with cue elevation.
8. Swerve occurs with practically all English shots because the cue must be elevated to clear the rails.
9. Swerve is delayed with faster shot speed.
10. Swerve occurs only while the CB is sliding; once rolling begins, the CB heads in a straight line.
11. Swerve occurs earlier with sticky cloth and later on slick cloth.
12. Swerve occurs earlier with a follow shot than with a draw shot.
13. Swerve angle is larger with a draw shot than with a follow shot.
14. Swerve angle can be predicted and visualized using the Coriolis masse-shot aiming method presented in my November '05 article.
15. For small cut angle shots (i.e., fuller hits), the amount of CIT does not vary with shot speed, but increases with cut angle.
16. For larger cut angle shots (i.e., thinner hits), the amount of CIT is significantly larger for slower speed shots as compared to faster speed shots.
17. The amount of CIT decreases some with larger cut angles, but not by much (especially for slower speed shots).
18. Maximum CIT occurs at close to a half-ball hit (30-degree cut angle).
19. In general, throw is larger at slower speeds, and for stun shots.
20. Both follow and draw reduce throw, and they do so by the same amount (see my October '06 article).
21. The largest discrepancy between throw values for stun and follow/draw shots occurs close to a half-ball hit (30-degree cut angle).
22. The difference between the throw of stun and follow/draw shots is not as great at larger cut angles.
23. More English gives you more SIT only up to a point. Additional English beyond that point actually reduces the amount of SIT (i.e., more English doesn't always give you more throw).
24. SIT is largest for a slow stun shot with about 50% of maximum English.
25. The amount of throw can increase significantly as a small amount of English is added, especially for a stun shot.
26. SIT is independent of speed (i.e., the throw is the same at all speeds) for small amounts of English.
27. "Gearing" OE results in absolutely no throw. The amount of English required for "gearing" increases with cut angle. At a half-ball hit, the amount of English required is about 50%.
28. At very small cut angles, IE and OE create similar amounts of throw (although, in opposite directions).
29. For large cut angles, a small amount of OE can result in more throw than shots with no English.
30. For large cut angles, IE results in less throw than shots with no English.
31. IE increases throw at small cut angles, but actually reduces the amount of throw at larger cut angles.
32. OE can cause throw in either direction depending on the amount of English and the cut angle.
33. Even for large cut angle shots (thin hits), excess OE (more than the "gearing" amount) can be applied to throw the OB in the SIT direction.
34. The amount of throw with IE can be much more consistent than with OE if the amount of English varies a little. In other words, the amount of throw varies more with tip placement for OE vs. IE. This might explain why some people prefer using IE on cut shots ... because they can better anticipate and adjust for the amount of throw.

ball compression effects

Does the size of the contact patch between the CB and OB vary with cut angle and speed, and does this affect how I should aim shots?

from Bob_Jewett:
The contact patch is larger according to how much energy is transferred from ball to ball, so a thin hit will have a smaller patch than a full hit, and a harder shot will have a larger contact patch than a softer shot.

One thing to remember in this, that a lot of people seem to be confused by, is that the size of the contact patch has absolutely nothing to do with the aiming accuracy required on a particular shot. The patch width does not give any indication of how precisely the cue ball must hit the object ball to get it into the pocket. In the same way, the contact patch of the tip on the ball gives no indication of how accurate you must be in tip placement to achieve a particular precision of placement of the cue ball.

depth perception

Is depth perception important in aiming?

Assuming you have already visualized the required impact line and ghost ball target (see online video demos NV 3.1 and NV 3.2), aligning the cue stick with the aiming line direction does not require depth perception. (In fact, the parallax created by binocular vision, even with a dominant eye, can make straight-line sighting difficult.) Now, some people might adjust their aim while in their stance based on their perception of the "angle of the shot," impact line, contact point, and/or ghost ball target. In that case, depth perception might be helpful.

I think a low stance helps one better align the cue with the desired aiming line, whithout requiring too much of a shift in eye (or head) motion between the CB contact point the aiming target, while fine tuning and verifying one's aim.

from Qtec:
The difference between short and long bridge is that the EYES are further away from the QB when you play with a longer bridge. This means that when you focus on the QB or OB, you will see more of the shaft [ie. a longer line ] and therefor its easier to line up the cue on the line on the shot.

dominant eye

Is one's dominant eye important in aiming?

I think this is debatable, and it might vary quite a bit from one person to the next. Now, head and eye position relative to the cue can be important in perceiving the desired tip contact point on the cue ball, especially if the cue tip is not help close to the cue ball when lining up a shot.

Vision and perception are too complicated and personal to simplify into a "formula" that works for all people. The focus should be on results. Each person should find the head position and sighting technique that helps them create the most accurate cue tip contact point and aiming line.

Here's an easy and free way to check visual alignment: Place the cue at cue-ball address in your elevated stance (so you can clearly see center-ball alignment), then get down into your stance, without moving the cue. Alternatively, have a friend position (and hold) the cue for you, with center-ball alignment, after you are down in your stance. Then move your head left and right to see how the perceived alignment and aim changes with head position. You might be able to find a head position that gives you more accurate alignment perception.

from RSB_FAQ:
For most people, one eye is much more dominant in seeing alignments than the other. Typically, right-handers are right-eyed, and vice versa. About 5% are "cross-dominant" (e.g., right-handed and left-eyed) and some are "ambi-ocular" (no dominant eye). To aim and sight well, it helps to locate your dominant eye directly over your cue. For cross-dominants, this may call for some adjustments in stance or neck/head angles. For ambi's, the stick will be under some spot between the eyes.

Here's how to test yourself: Hold your thumb up at arm's length, visually blocking some distant object (for example, a clock or a lamp). Don't focus on your thumb; focus on the distant object. You'll see a ghost of your thumb, since your dominant eye will be in line with both your thumb and the distant object, while your non-dominant eye will be seeing past your thumb, directly toward the distant object. With one eye seeing the thumb and the other not, you get a ghost. The ghost is centered on the distant object because your dominant eye is the one that tells you what's lined up with what.

So, when you close your non-dominant eye, the thumb becomes solid instead of ghostly, since the dominant eye is looking directly at the thumb. When you close your dominant eye, the thumb appears to jump to the side because the dominant eye (that was making the thumb line up with the distant object) is not in use.

Stroke into a mirror to see where your dominance spot is, relative to your shaft. It "should" be directly over the shaft. If it's not, but you're not having difficulty aiming or sinking balls, don't worry about it.

from JoeW:
I have created a way that you can determine the best way for you to aim and it won’t cost anything except a little time and maybe $3.00. Brought to you by Easy Pool Tutor for free (it might even wind up in the CD but the Admin will have to decide that). I present it with no strings attached.

Photo 1 shows the table with a line drawn from the head to the foot of the table on the center diamond. I used a dressmaker’s marking pencil (cost $1.00 at Wal-mart) to draw the line. I left the pencil on the table for this photo.

For a ruler I used an 8’ piece of metal wall board corner molding ($2.00 at Home Depot). Note that the line goes from one end of the table to the other.

Photo 1

The balls are set with the base of the One ball on the line (see Photo 2) with the center of the numeral One centered on the line. If you look over the top of the One ball you can see the other side of the ball and that the number One lines up with the white line. Go to the other end of the table and set the Three ball in the same way.

The balls are now lined up perfectly. If you hit dead center on the One, stop on the Three ball the three ball should bank off the end of the table and come back and hit the One ball – a really tough shot.

Photo 2

Ok so how should you aim? Well first lets get the bridge hand out of the way. To do this I reversed the table bridge and set it where the stick will line up perfectly with the center of the One ball. See Photo 3. I am holding the table bridge with my left hand and site with my eyes and the right hand. Here is the interesting part of this technique.

As I look down the shaft and line up from the One to the Three I get what I think is a good site picture. Notice where your nose is relative to the shaft of the cue stick and this is your site picture.

Now raise up a little bit and you can see over the Three ball to the head rail and you can see the white line. If everything is lined up then you are straight for your site picture. If not, something has to change.

Shooting the shot by stopping on the Three ball and watching the return from the rail will tell you if you site picture is the least bit off. This is a difficult shot and you have to be lined up perfectly. All I can tell you is --- things will change.

Please try it. By the way, you will learn if you shoot most accurately with one eye or with two eyes.

Photo 3

BTW, I learned that I shoot "best" with the my nose slightly closer to the cue stick than I had it before using this test.

from Billy_Bob:
Here is more reading about the dominant eye...

Ken Tewksbury, Master Instructor (See #6)...
http://www.tableskills.com/article-kt2.php

Robert Byrne: "If you are having trouble pocketing balls, it may be that you aren't bending over far enough and aiming the cue like a rifle with your dominant eye."
http://www.byrne.org/pool/tips/08-1998.html

Says Buddy Hall wrote good article on this: Billiards Digest in June 2001...
http://www.ez-shot-ghost-ball.com/dominant_eye.html

By Don 'The Master' Rose, BCA Advanced Instructor...
http://www.azbilliards.com/donrose/lesson4.html

fractional-ball aiming

Are fixed-line of aim, fractional-ball aiming systems like Hal Houle's method useful?

Various aiming methods (even though they are not perfect) do help some people aim, concentrate, focus on the OB, stay down, and shoot better. I don't think anybody (even me) would say that is a bad thing. On the other hand, people should realize that fixed point aiming systems with a limited number of aiming lines are not perfect and will cause you to miss shots if you don't compensate (consciously or subconsciously).

Hal Houles basic aiming system is an example of a fixed-line of aim method. It is described here. Basically, the claim is there are only three different aims for all cut shots: a "15-degree cut," a "30-degree cut," and a "45-degree cut." In TP A.11, I show that these aims are equivalent to 3/4-, 1/2-, and 1/4-ball-hits and the 15- and 45-degree angles are not exact. Also, I show an example shot "in between" two of the aim references to show a deficiency of the method. The method provides easy visual aiming, and it helps a player establish good reference aims for different ranges of cut shots; but for "in-between" cut angles, one must adjust or compensate between the aim references.

I know believers of the Hal system have much anecdotal evidence. In fact, if a method works for somebody, that's all that really matters. It is difficult to refute anecdotal evidence. So I'm not saying going to say his method doesn't work. I just think that it is not as much of a silver bullet as some people think.

For a given shot, with N different lines of aim, assuming you can hit where you are aiming, the object ball can go only in N different directions. Depending on where a pocket is and how far it is from the object ball, the cut shot may or may not be makable with one of the selected aiming lines.

Even with English effects (squirt, curve, and throw) and cling (collision-induced throw), the object ball can still go only in N different directions for N lines of aim for a given cue stick elevation and shot speed, and for given ball and table conditions.

See TP A.13 for background and specific results. Here are some highlights:

Now, I still think the three fractional aiming references (1/4, 1/2, and 3/4) are very useful because they are very easy to visualize. And having easy to identify references is always useful (e.g., as with the tangent line and the 30 degree direction for predicting CB motion), so I agree 100% that the aim points (Hal's or fractional aiming or any other system) provide a good framework from within to work, especially for people that have difficulty aiming accurately and consistently.

from Spiderman:
Like all "discrete", "fractional-ball", and simililar aiming systems, it gets you in the ballpark for most shots and depends upon subconscious correction to make the fine adjustments. In other words, you have to use it as a guide, "take it on faith", and shoot the shots.

For a beginner, it will get them in the ballpark and they'll accidentally pocket more balls than by winging it. For an intermediate, they may have enough experience that they will subconsciously correct, and the system might work well for them. The expert doesn't need a system to get them in the ballpark.

All discrete systems have the same failing - they are not geometrically correct for all setups. If you claim that there are only a (small) discrete number of aimpoints required to hit any pocket from any setup, and disallow the subconscious correction factor, all such systems may be easily disproven. In practice, your ability to compensate overcomes the built-in flaws of the system.

ghost-ball aiming

How does ghost-ball aiming work?

The ghost ball (GB) is the imaginary position the CB must be, at contact with the OB, to make a shot. It is easy to practice visualization of the GB target by having a helper place a real ball in the desired GB location (adjusted for throw or not) and pull it away when the person shoots. I demonstrate this technique in NV 3.1; although, I didn't have a helper to remove the ball for me.

Also, striped balls are useful to help the shooter visualize both the "aiming line" (from the CB to the GB center) and the "impact line" between the GB and OB centers. To me, that's the most useful advice in the video.

 

Supplemental Aiming Method (SAM)

What is SAM?

The Supplemental Aiming Method (SAM) is a fractional-ball aiming method taught by many BCA instructors.

from caedos:
S.A.M. is the set of aimpoints for the fractional aiming method. It is the inverse (almost exactly) of the system CJ Wiley has on his Volume 3 of 'Ultimate Pool Secrets' video. If you can roll your cue-ball in a straight line to the same point on an object ball over and over again, it will produce the same resultant path for the object ball over and over again. The contact point between the balls is not relevant to the shooter using the system, because it will happen automatically just by shooting the cue ball to the correct aimpoint. A straight shot is a #1 Aim in S.A.M. and only requires you shoot the cue ball in a line to a point on the vertical center of the object ball. This is usually done with the aimpoint being where the object ball touches the table or at the topmost part of the object ball (tougher to be precise but has better lighting). A half-ball hit releases the object ball from contact at about 30-degrees from the cue ball path (not the cue-ball to object ball line), and is the #3 Aim in S.A.M. This is the second reference for me after the #1 when I'm shooting because it has a well-defined aimpoint, the outermost edge of the object ball away from the object ball target (the pocket, most of the time). The #2 is halfway between, but uses a point on the edge of the object ball to aim at and not the body of the ball (it's tough to pick a point in the middle of a solid colored sphere); #2 releases at approximately 15-degrees. #1 is straight on, #2 is a 3/4 full hit, #3 is half-ball, #4 is 1/4 ball, #5 is 1/8 ball, and #6 is Thin. Fractional aiming has been around for a long time, and this system is another way to use it to greater effect. The #4 is hit by estimating your aimpoint onto the felt beside the object ball or by matching the #2 inside aimpoint position on the cueball to the #3 aimpoint outer edge of the object ball. #5 aimpoint is a similar estimate, and because the edges of the cue-ball and object ball are receding very quickly the penalty for error seems more extreme; I tend to leave S.A.M. for the #5 (1/8th ball hit) because I focus on the amount of ball overlap and not a point on the felt. #6 is for Thin cuts and is often taught by aiming through the contact edges of both balls and parallel shifting to the center of the cue-ball. There is no exact science that will produce a perfect aiming system. I agree with Bob Jewett when he said something to the effect of needing to know what stinks about a system before being able to use it well. What stinks to me about this system is that there is an intangible quality that appears when using the system because the subconscious mind has to be allowed to use the mind and body to make the shot look, feel, and become 'right'. This means you can say a shot is a #3 Aim all the way and maybe it's really a #3.463024 Aim or a #2.903882 Aim. If you want to play pool you will either call it a #3 and let your brain do the rest, you will use a #3 Aim as the reference and let your brain thicken or thin the hit to make it right, you will find some other way to make this system work for you, you will abandon the system for something else that makes more sense, or you will have a nervous breakdown and take up checkers because the checks taste better when the thorazine kicks in. This is a crude explanation of S.A.M. The assumption is that the shooter will use the cue stick as the pointer for the line the cue ball needs to travel down to get to the aimpoint (a specifically chosen point at the end of that line), thus making the cue-ball travel an easier task. The shooter then lets the stroke work and the cue ball has no choice but to go down the line. It's less stress. Having an aimpoint to shoot directly at removes confusion over contact points and simplifies the process so that the shooting routine completes a circuit with no loose ends and has the added benefit of a complete command structure, leading to a more focused shooter. K.I.S.S(illy).

using lights and ball reflections

Can lights and ball reflections be useful in aiming?

I think the value of this is debatable, but some people do claim it is useful. This article describes a possible approach for using reflections of lights in balls.