Slow sync flash photography

When shooting subject with low light situation, you got only two options; either to shoot with a flash or to shoot with a slow shutter speed. 

With the flash, your subject will be lit well and if the subject is moving then it will be frozen and as a result will be sharp. problem with this is, no time to capture ambient light and cannot capture motion blur.

With the slow shutter speed, you will have enough time capture the ambient light and still subject, what if the subject is moving? you will capture the motion blue, and also the blurry subject.

You can achieve motion blur with sharp subject using "Slow sync flash".

Focal Length : 29 mm, Shutter Speed : 0.6 sec, f stop(Aperture) : f/5.6, ISO : 400, White Balance : Auto

Have you heard of Rear and Front curtain sync or flash?

Rear Curtain sync instructs your camera to fire flash just before closing the shutter.
Front Curtain sync instructs your camera to fire when exposure begins or right after shutter opens.

Mount your camera onto the tripod, then lock the focus.. once everything set, put your flash to manual mode and make the power of flash to 1/3. Now put flash to rear sync. Once you click the shutter release button, move your subject, at the end of the exposure camera fires a flash to freeze the subject. Look at the result.