What the frame includes and why
Framing decisions are usually described by what they show, but they are better understood by what they refuse to lose. The cowboy shot refuses to lose the hands.
In a Western the hands are the plot. A face can be impassive, dialogue can be sparse, but a hand hovering near a holster carries the entire tension of the scene. Cut to the waist and that hand leaves the frame. Pull back to a full shot and the face becomes too small to read what the character intends. There is exactly one band of framing that keeps both, and it starts around mid-thigh.
The lower boundary follows a general rule of framing that has nothing to do with cowboys: do not cut at a joint. A frame line through the knee or the ankle looks like a mistake, because the eye expects a joint to articulate and the cut amputates it. Mid-thigh and mid-calf both read as chosen. Mid-thigh happens to be exactly where the holster sits.
What it does dramatically
Three things follow from the geometry.
- Stance becomes legible. Weight distribution, whether the feet are set, whether the shoulders are square. All of this is performance the audience can read.
- Hands stay in play. Anything held, drawn, clenched or reached for stays in frame without a cut to an insert.
- Status is neutral. The shot is conventionally taken at eye level, so it neither elevates nor diminishes the subject. Combined with the readable stance, it reads as a confrontation between equals.
That last point explains why it is a standoff frame rather than a conversation frame. Dialogue wants the face; confrontation wants the body.
Prompting it
The term itself is well represented in training data, so naming it works, but it works better with the geometry spelled out.
State the cut explicitly: framed from mid-thigh up. Models interpret shot names loosely and will drift to a waist-up medium shot without it. Then name what the hands are doing, because the whole point of the frame is that they are visible: hands loose at his sides near the holster.
Add the camera height, since the neutral status reading depends on it: at eye level. A cowboy shot from a low angle becomes a hero frame and from a high angle becomes a diminished one, both of which are useful but neither of which is the default.
Keep the lens moderate. Around 35mm to 50mm holds the stance without distorting the legs, which is what a wider lens does when it is close enough to fill this frame. For the classic look, put the subject against depth rather than a wall: a street, a horizon, a corridor. The framing was built to show a person standing in a space, and a flat background wastes half of what it buys you.