Composition
There are two different ways of using slow shutter speeds. First, using a tripod to keep scene sharp while the slow shutter allows moving objects to show up as a blur. Secondly, you can use a slow shutter while panning along with your subject. In this second case, the subject will be relatively sharp while the background will be blurred. In both cases, the slow shutter speed will give a sense of motion.
Slow Shutter while using a tripod: While the camera is stable on tripod, you will adjust your ISO to the lowest possible setting (ISO 100), an aperture of F16, and then adjust the shutter until you get a correctly exposed image. (lets call it 1/20 second for now)
Since you are shooting from a tripod the landscape will be sharp however, the slow shutter will allow the moving parts to be blurred. (Below)
EXERCISE: Find a model such as family member or a pet. Keep the posing simple. For example have a family member type on the computer or have your puppy eating from their food dish. Set the camera on a tripod and set the ISO to 100, set the Aperture to F8 (this may need to change, but for now F8 will work), and the shutter speed will need to be adjusted until the exposure is correct. Now shoot several shots as your model is going about their business. See sample below and note the movement in the hand.
This same technique is used to create a milky waterfall. Place the camera on a tripod. Set the ISO to 100, Aperture to f22 and then adjust the shutter speed until you get the correct exposure. For best results, you want to shoot in the late afternoon/evening when it is darker as you will get the desired slow shutter speed.
Whats happening here, is that the camera is on the tripod so the overall scene will be sharp and unblurred. However, the water is moving and therefore it will appear milky/blurred in the final shot.
Note: You will need to experiment and then experiment some more. If you have waterfalls or running water close by, it certainly helps.
EXERCISE: Set your camera on a tripod and frame the water the way you like. Set the ISO to 100, aperture f22 and start with a 1/30 second shutter speed. Then adjust the shutter accordingly to make the photo brighter or darker.
The second technique that you can use to show motion is called panning. The effect we are going for with panning is to have our moving subject sharp and focused while the background is blurred. Panning isn’t easy and the failure rate is high, but when you get it right, the results are fantastic.
To start, you cannot use a tripod. Set the ISO low (ISO 100), an aperture of F8 and adjust the shutter until the exposure is correct. Now, when you are shooting a moving subject like a car, a kid on a bike or bird flying, you will need to smoothly move and follow the subject while shooting in Continuous Drive.
EXERCISE: Set the ISO to 100, Set the aperture to F8 and then adjust the shutter speed to get the correct exposure. Now when you are shooting a subject like a passing vehicle, or kid on a bike or your pet running in the yard, you will need to keep the camera moving at the same speed as the subject. Shoot in continuous drive and shoot lots. there will be many missed shots. That’s part of the deal at these slow shutter speeds. In this shot (below) I probably took 80-100 shots and had a half dozen keepers.