You will need a camera with a Second Curtain flash mode or one that accepts external flashes. In this hack, I used a Canon 5D with a Canon Speedlite 550EXII. When shopping, it is imperative to check camera specifications carefully.
To proceed, set your flash to Second Curtain mode available in the controls. Put the camera in Manual Exposure mode and use a beginning setting of one second at f-5.6.
You should also pay attention to your background. You would need one that differs in tone and/or color from the subject to get a better result. Usually, these types of photos are shot with a light object on a dark background.
Put the object in motion and trip the shutter. You will hear the click of the shutter opening, but no flash – at least not yet. When the shutter clicks again to close, the flash will fire, that’s the second curtain. The shutter is open, capturing the object’s movement, and the flash fires right at the end of exposure, freezing the subject in mid flight and thereby rendering a natural-looking composition.
You may need to take many test shots to perfect the composition, lighting of the scene, and motion of the object. The length of the trail is determined solely by the length of the exposure time (given that you don’t have any control over the speed of the subject). The intensity of the motion trail is determined by the strength of the ambient light on the subject, as well as the camera’s ISO and aperture settings. The intensity of the frozen image at the end of the exposure is determined by the flash strength. To take control, put the flash strength on manual control; this feature typically requires an external flash.