In order to get a clear photograph of your water photograph you need to have the accurate level of light. Because most flowing water images are done outdoors you will have to prepare yourself for different weather. You will also need to be able to work with natural light in an effective way. Let’s take a fountain for example. Fountains in the city can supply beautiful, creative shots. We can try to take photos of them two ways. We can shoot the motion of the water to give the appearance like a silky-smooth ribbon. Alternatively, we can shoot the flowing water so we see every drop.
These two things depend a lot on your shutter speed. A speedy shutter means that you can stop the action. This means that you will be able to spot every droplet of water poised in the air as it shoots out to the fountain. To do so, you need a large amount of light so that you can have a fast shutter. A slow shutter speed means that you can slow the speed of motion. This produces what is called a silken effect. A silken effect is where your shutter speed slows down and the water seems like it is streaking across your shot. You also need to carefully watch your light so that you do not overexpose your photograph. So how does this become applicable?
Let me go into more detail. The longer you have your shutter open, the more light enters the sensor. It works the other way, too. The quicker your shutter speed, the less light that you have to work with. You must find the balance between what outcome you want to create and your lighting. For example, you wanted to photograph the water fountain on an dull day. Perhaps there are clouds approaching and producing some overcast light. You already have in mind that you want to stop the motion of the water so you can see each separate water drop. You know that you need a fast shutter speed to do this, but there is not much daylight in the scene. So how do you get a fast shutter speed so you can stop motion and be able to get just the right amount of light?
You would choose a very high speed of the shutter. 8000th of a second may be your favorite. However, you see that the camera is telling you that to capture at the speed you are going to have a very underexposed and dark photo. This will not suffice at all, therefore you select a wide aperture. Remember, a wide aperture will blur your background. This might be okay given the situation. So, consequently, you choose f/4. An aperture this large will let a lot of daylight in.