Originally Posted by Gut4Tennis
The net person, being at the service line, can easily see if there is space between the baseline and ball on a slow moving lob or moon ball nuff said
I also have to agree with this. There have been several times when I've played with partners who thought balls at the baseline they were hitting were in but myself and someone calling the lines saw it as out. The ball bounces so quickly that your brain cannot tell 1" in or 1" out because the bounce happens and your brain cannot pickup if the view you saw as out was BEFORE or AFTER the bounce. It's very easy for someone at the baseline to see it in as opposed to out, especially when they're right on top of the ball, midswing, and making contact to return the shot. That's why most of those balls are played out on hard courts... because you can't generally check the mark after you hit it unless you see fuzz. On clay it's different and even I have hit the close ball back, then called it out if the mark looks out... regardless of what my return shot did. Don't misunderstand, the calls is almost right after the shot and at the end of my followthrough. I look down and see. If I see the mark and it's out, I yell "No or Out". No one usually makes a big deal out of it because they can see the mark and they know how hard it is to make the calls when you're on top of them like that.