Everything in today’s world is auto this, auto that, immediate feedback, connectivity based, etc. We expect everything to be fast and work perfectly. We make a purchase and want the item to do exactly what we want, when we want it and how we want it. Good news—today’s DSLRs can do this. Bad news—if you set the camera to auto this/auto that or Program, it will provide proper exposures, but you may not obtain the look, depth or feel you wanted when you pressed the shutter. Enter the world of Aperture 101 to control it for EVERY picture. Use this primer and overview to learn WHAT apertures do and HOW to control them.
Control Depth Of Field: Depth of field is the range of sharpness starting with the most foreground element extending to the one farthest from the camera. Pictures with a lot of depth of field have everything in sharp focus through the entire image. Pictures with narrow depth of field depict the primary element as sharp and everything in front and in back fall off. The aperture controls depth of field. Those in the range of ƒ/1.8, ƒ/2, ƒ/2.8 and ƒ/4 limit depth of field. Apertures of ƒ/11, ƒ/16 and ƒ/22 increase depth of field. Note that ƒ/5.6 and ƒ/8 fall somewhere in the middle. ƒ/1.8, ƒ/2, ƒ/2.8 and ƒ/4 are referred to as opened up, while ƒ/11, ƒ/16 and ƒ/22 are referred to as stopped down.
Lens Choice and Aperture: Depth of field is more limited with telephoto lenses. Wide-angle lenses provide more depth of field. If the goal is to create an image with infinite depth of field, use a wide lens and stop it down to ƒ/16. This combination is advantageous when making landscapes. If the goal is to narrow the depth of field, use a telephoto lens and open it up to its widest aperture. Think portraits or any other situation where you don’t want an in-focus background or foreground to be a distraction.
To see how depth of field works, place your camera on a tripod, put your camera in aperture priority mode, and photograph a subject eight feet away. Place the subject approximately six to 10 feet from the background and foreground. Focus on the subject, set the zoom to its widest setting, and make a series of photos at every full f-stop starting at the widest opening and continue to the smallest one. Repeat the process using a medium zoom setting. Repeat it again at the most telephoto setting. When you review the photos on your computer, you’ll see how the aperture and zoom settings go hand in hand with what I have above. The widest angle and most stopped down shot will show the most depth of field. The most telephoto and fully opened up shot will show the least. Use the metadata in the file to see the exact settings at which every photo was made and apply your findings to future outings.
Control The Amount Of Light: The aperture also controls the amount of light that strikes the sensor. Above, I mentioned the difference between an open and stopped down aperture. To review, open apertures are ƒ/2, ƒ/2.8, ƒ/4, etc. They’re referred to as opened up in that the openings that control the amount of light are open to their widest capacities. The wider the opening, the more light. If a window shade is fully open, more light enters the room. Stopped down apertures are ƒ/16 and ƒ/22. They’re called stopped down because the openings that control the amount of light are closed down to their smallest size. The smaller the opening, the less light. If the shade is just slightly opened, the room is barely illuminated.
The amount of light controlled by the aperture has a direct relationship to the required shutter speed to provide a proper exposure. If the aperture is wide open, it goes hand in hand with faster shutter speeds. This works to your advantage if you handhold the camera because your images will be sharper as there’s less camera shake. If the aperture is stopped down, it goes hand in hand with slow shutter speeds. The slower the shutter speed, the greater the chance the camera will move during the exposure and net a soft image. In instances where it’s necessary to stop the lens down to obtain a lot of depth of field, it’s essential a tripod is used. This is why you see landscape photographers use tripods. Landscapes require lots of depth of field. To get the depth, a stopped down aperture is necessary. This means the shutter will be slow, so a tripod is mandatory. I hope this “sheds some light” on what an aperture controls and provides some insight into why it’s so important to get your camera off auto and learn to use Aperture Priority to bring your picture-making skills to the next level.
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