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Using Creative Apertures For Portraiture - Here are some top tips for using apertures to create great portraits.
Aperture is very important when it comes to portraiture as it controls how much of the background and foreground is in focus, which has an effect on how much of the focus is on the subject of your portrait. The Tamron 70-200mm lens is a very versatile lens with a maximum aperture of f/2.8, making it ideal for throwing the background out of focus.
Depth-Of-FieldWhatever the main focus of your image is when you focus on it, it will appear sharp. However there is also an amount of front and back sharpness in front of and behind the main focus point and this is referred to as the depth-of-field. You can experiment with your depth-of-field to see what works best. Your camera might have a depth-of-field preview button, letting you see how much depth-of-field you have before taking the shot.
The amount of depth-of-field within an image depends on several factors:
- The distance between the camera and the subject. The closer the subject the more shallow the depth-of-field. With distant scenes, therefore, there is plenty of depth-of-field.
- Choice of lens aperture. The wider the lens aperture (ie /2.8, f/4) the shallower the depth-of-field, and the smaller the aperture (f/16, f/22) the greater the depth-of-field.
- Focal length. Contrary to popular belief a wide-angle lens does not give greater depth-of-field than a telephoto lens if the subject magnification is the same. You can test this for yourself. Take a frame-filling head shot with a wide-angle lens (you will have to get close to the subject, so warn them!) and then do the same frame-filling shot with a telephoto – this means backing away from the subject. Use the same aperture for both and you will see that the depth-of-field is the same.
Photographing PeopleIn terms of portraits, especially outdoors, wider lens apertures are often best because they throw the background nicely out of focus. How effective this is depends on the scene and focal length as well as aperture choice. If your subject is standing quite close to a distracting background even shooting at f/2.8 or f/4 will not throw the background out of focus. But bring the subject forward a couple of metres should work nicely.
Bokeh BackgroundsHow the background is thrown out of focus depends on the lens. Bokeh is the term used to describe the pictorial quality of the out of focus blur. Lens design and aperture shape play a large part in how effective its bokeh is so do try it with your own optics. A good test is shooting a close-up portrait outside against a background with some bright pinpoints of light, ie sun glinting off water, car lights, streetlamps etc.
Of course, you might prefer greater sharpness in your backgrounds and that is when small apertures are used. The important thing is to keep your eye on the background and if it looks messy or cluttered use wide apertures rather than small ones.