if I want to film bits from my hitting, like from the back of the court, what’s the best way to do it? do I need a tripod? how do you do it? and how do you prevent the ball hitting the camera if you’re filming from the back?
1) A camera from the side of the stroke - the side with the forehand & ball or backhand & ball works over a wide part of the baseline.
2) With a ball machine the incoming balls can be struck in a more limited area across the back of the baseline.
3) A camera can be placed on a tripod outside the fence. To be sure that the ball does not get through the fence a piece of plywood with a hole, wires or other things can be placed on the fence so that the ball can't fit through the fence. Probably a hole in a piece of plastic, for example, side of a milk bottle could be placed on the fence to stop the ball from getting through.
4) Smartphone cameras have a wide angle lens and HD video. For high speed video, 240 fps, the video file sizes can become large for 2-3 minutes of ground strokes.
5) It is always a big plus to show the bounce of the ball on the other side of the net. Higher camera positions can show the far court and bounce.
6) I recently purchased two old used Casio FH100 cameras and they do an excellent job at 240 fps with manual exposure control. ~ $100.
7) If you want to work on stroke changes, set up for that in a fixed space, preferably with a ball machine.
8) If you want to see what you are doing in a rally or match situation place a wide angle camera higher behind the fence or mounted on the fence (consider risk to camera). I covered the baseline with a camera behind the fence and a 24 mm lens (24 mm equivalent to a 35 mm camera's field of view.)
9) A cheap way to mount on a fence would be to buy a cheap tripod with an elevator adjustment, $20, and find a way to mount it on the outside of a fence. For example, fix the tripod to a piece of plywood with cushioning between the plywood and fence. The tripod head allows pointing the camera and the elevator adjusts the camera position to look through the fence.
I think the camera on a tripod is most at risk from the ball hitting the tripod and knocking it over.
I've posted on mounting cameras before.
Most video cameras have automatic exposure control. To get the camera to select a fast shutter, video in direct sunlight since it has about 50-100X as much light as indoor tennis court lighting. Low light levels result in slow shutter speed and excess motion blur.
I found it useful to use a 60 fps camera with a fast shutter to look at matches. The camera was behind the fence on a tripod, the center of the court. You can see many stroke flaws with clear 60 fps. 60 fps is not adequate for the faster motions.
I have videoed ground strokes with a ball machine at 240 fps. A 2 or 3 minute recording at 240 fps takes some time to look through or edit. If you want to work on strokes, video only a few strokes and look at what you have on the court.