Yeah, I think this is the real crux of the matter. How sure do you have to be to call a ball out?
- A ball that you honestly couldn't tell whether it was in or out? Easy, call it in and play it.
- A 120 mph serve that looks like it lands 3 inches past the service line? That's harder. It looked out... but most people's eyes aren't strictly reliable at that speed and that kind of margin.
- A ball whose trajectory looks like it's landing 6 inches long at the baseline, but lands somewhere near your feet and you don't actually see the bounce? Another hard one. No one really sees balls landing right at their own feet accurately.
- A ball that you clearly see land a half inch outside the sideline? Most people see the sideline pretty clearly. Still, are your eyes reliable at a 1/2 inch?
I think most honest people call balls out somewhere between "I suspect the ball was probably out," and "I'd bet good money the ball was out." But just about nobody I've ever played gives up so much of the lines that they're absolutely certain every ball called out was actually and truly out. You'd need the ball to be a foot or two out to call it against anyone who hits with much pace.
In fairness, I think some people feel a lot more certain of their eyesight than they have any right to. But for people who have a realistic opinion of their own ability to precisely see where a fast paced ball landed - I don't think anyone makes calls based on 100% certainty but based on a reasonable degree of doubt.
I never thought about this till now, but ill try to explain my "margins" based off of how I tend to call the lines.
-Service line long: I give about 3 inches on flat serves. If it looks to be about 3 inches long, it was probably long, even if it was only actually long by less than an inch. Second serves (kick serves) ill give about an inch or more, but this is only because you cant tell if the ball is going to be inside the line, or a few inches long when it leaves the racket. Because a kick serve ball will contact less of the court, you can be a little more sure about where the ball actually hit vs. a flat ball that will skid. You have the worst vantage point for these calls.
-Service line wide: Balls that spin in towards the line ill give an inch or more. Like with kick serves, you cant tell if the ball is going to spin in or not when it leaves the racket. Balls that spin away from the line, im more confident to call down to less than an inch, depending on the speed. If it's a big first serve that looked in inch wide? I'll probably call it good. If it's a second serve? I'll probably call it wide. You have the best vantage point for the wide service lines.
Baseline calls are a bit harder to estimate. A ball could be landing at your feet, behind you if you've been passed or lobbed, or you might be running at full stretch trying to get to a drop shot from the opposing corners baseline.
I think the bottom line is that, over the long-run, people will be able to figure out if you're calling shots out because you're trying to hook them or because you genuinely thought it was out. It's hard to say over just a few calls because the variance is higher; you need a large sample size against the same opponent. I just try to play by the "I have to be sure it's out to call it out" rule and don't sweat the small stuff. I'll end up losing more points that way than if I had taken a harder line but c'est la vie. Maybe it'll come back to me in karma and maybe it won't. That's not going to change how I make the calls.
While I mostly agree, you will still play people who question your calls every time it means they dont get a point they think they deserve. Some people are just angry, unrealistic and suspicious like that.
I've literally played with a guy who questioned my line call on a ball served 6 inches wide. I hit the same serve on that guy and he called my ball "way out." I can tell if a ball is going to be 3 inches long/wide on any ball that I hit the moment it leaves my racket, so I knew it couldnt have been "way out". I didnt say anything then, but I did ask my partner what he saw, and he said "there was a mark, and it didnt look like any part of that mark was outside the line." and we laughed.
In summary, I think you can figure out how ethical of a player you are based off one thing. How often do you challenge calls that work against you? If you challenge calls made by opponents that work against you, I think it's safe to say you're calling your own lines fairly no matter who ends up getting the point.
