Continuous release isn’t just useful for fast moving subjects, it’s also handy for times when you just barely have enough shutter speed to get a sharp image while hand holding.
Pressing or releasing the shutter button, regardless of how smooth you try to be or what technique you use, you will always move the camera a little bit. However, once you’re holding the shutter release down that motion is gone. In many cases this can make the difference between a sharp image and a slightly blurry soft one.
An example of how low you can go is evidenced here with sharp images being made at shutter speeds as low as 1/80th of a second with a 640mm effective focal length.
There are two ways the magnification of the lens is generally described.
To convert from the ratio form to the decimal form, divide the object size by the image size.
Some Common Magnifications