Ever so often I get something wrong when trying to capture a part of the screen. I’ve figured out two ways to cancel the action while doing the capture.
If I haven’t yet right-clicked to choose the starting point of the capture area, I just click the right mouse button to cancel out the capture.
If I already started choosing the capture area by left-clicking and started dragging out the area, I simply click the [ESC] button to cancel out.
That’s it, I hope you find it useful.