Beginner Photography Tips - Understanding Aperture and Depth of Field
Have you ever wondered why the shot that looked so good through the viewfinder just doesn't look right when you view it later? Odds are it is because you are not in control of your camera, specifically your aperture. The aperture is one of the two options for controlling the exposure. Aperture and depth of field will be the focus of this piece about beginner photography tips.
Aperture refers to the size of the opening through which the light can reach the film or sensor. The wider the opening, diaphragm or hole, the more the light and therefore the faster the shutter speed you can use. But, the aperture has a very important creative aspect to it. The aperture also plays a huge role in the depth of field, the portion of your image that is in focus, or sharp.
The larger the hole (the lower the number of the aperture), the more shallow your depth of field will be. The smaller the hole, (the higher the number of the aperture) the greater your depth of field is.
There are other factors that influence the depth of field, including the focal length of your lens (wider lenses have a greater depth of field) and the zone of focus (the closer to infinity you have your focus the greater your depth of field will be).
When you look through your DSLR you are looking through what is known as a wide-open lens. That is, you are seeing through the lens when it is at its largest hole, or aperture, so that the viewfinder will be bright. If you have a 2.8 lens you will be looking through the lens at f2.8.
If you are not in control of your aperture (if you have your camera set on "P" or "Tv" thereby having it choose the aperture), that aperture may well be set at f 8. As soon as you press the shutter button the lens "stops down" to f.8, (which you don't see because the mirror has flipped up) and the picture is taken.
When you looked through the lens it is likely that your subject matter was sharp and the background pleasantly out of focus. But at F 8 that background comes more into focus and your picture might not look nearly as nice.
If your camera has a depth of field preview button you can press that and preview the depth of field before you shoot. The drawback is that the scene through the smaller aperture will be correspondingly darker. If you don't have that option, you can at least be aware of depth of field issues and check your LCD to see if you captured the look you wanted.
Check your F-stop and see what you are actually shooting at, and how that compares to what you are seeing. It may be that you might actually want more depth of field. Then you would set you f stop to as high a number (as small a hole) as possible while maintaining a shutter speed you can effectively work with.
Key to getting images that consistently have the look you want and expect is to understand your camera, how it functions and to be in control of the camera rather than letting the camera be in control of you.