Aperture and Depth of Field
Aperture is not built into the camera, but it is built into the lens. Aperture controls the depth of field and also controls how much light goes into the camera. It is also known as f-stops because as you seen in our previous scenario, I used f/4.5. Notice the “f” in f/4.5; this refers to the aperture value. The lower the aperture value, more light can enter the camera, which also causes the foreground to become blurry (many people love this effect). The higher the aperture value, the less light there is to enter the camera. This would result in a sharper image overall (Ideal if you plan to take very detailed images).
When I first began studying photography, I was most interested in shooting macro shots because of the beautiful bokeh effects. In able to have this effect, you will need a lens that has a larger aperture than your standard f/3.5 lens. Although a standard kit lens does provide decent macro images, having a lens with a much larger aperture range becomes useful when doing macro photography. A lens with a maximum aperture of f/1.8 is a very cheap solution, especially with the Nikon and Canon 50mm f/1.8.
Having a large aperture like f/1.8 is also very beneficial for low light shooting. Since the lens can suck in more light due to the larger aperture (smaller f number), you would not need to increase your ISO. Having a large aperture could save you from increasing your ISO, which would result in smoother images.
Keep in mind that adjusting aperture settings will also affect ISO and shutter speed. If you take a picture with an aperture setting of f/3.5 on a normal day, you can get away with something like ISO 200 and a shutter speed of 1/250. But if you change your aperture to something like f/8, you will have to increase your ISO setting and/or slow down your shutter speed just to get enough light and re-balance the exposure.
Remember, aperture is not part of the camera. It is only part of the lens, so do not expect an entry level Canon 650D with its standard 18-55mm kit lens to shoot at f/1.4; it is impossible. The best solution is to replace the kit lens with a much more expensive lens with a larger aperture.