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Learn about lens aperture

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How lens aperture settings can get you the photos you want

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Digital SLRs and their interchangeable lenses open up a world of great photo opportunities. But when you go to buy a new lens, why pay more or less? One very important factor is lens aperture. This article will discuss aperture, how to get the types of photos you want, and price considerations.

The lens you get in most camera kits
Most entry-level digital SLR packages include the body of the camera and a standard 18-55mm f/3.5-5.6 lens. This is a great package to start out with, but most people will soon want a different lens with a higher maximum aperture for more creative shots.

What is lens aperture?
Aperture is the opening in your camera lens that determines the amount of light that passes through to the sensor. Aperture is noted by f-stop numbers such as f/1.4, f/2.8, f/8, f/22, and f/32, which are the measurements (or fractional) of how far the lens can open to let light in.

Apertures work in much the same way as your eye's pupil. Too much light and the pupil will close in size to block the light out. Too little light and the pupil increases in size to let in more light. So when you change the f-stop, you are actually setting the size of the opening, or aperture, through which you capture photographs.

Aperture settings


What f-stop should you use?
Without getting too confusing and technical, an easy explanation is this:
  • The smaller the f/stop number, the less of your photo will be in focus.
  • The bigger the f/stop number, the more of your photo will be in focus.

How to fade the background and get a portrait that pops
Say you want to take a portrait of a friend. Using the typical lens (18-55mm f/3.5-5.6 lens) that comes with your camera, the subject and background will both look about the same as far as sharpness, with little visual appeal to your subject.

By using a lens with an f/2.8 aperture, you can fade the background and focus on your subject in the foreground. You'll get a much more dramatic shot as your subject will "pop" from the photo. The result is a more desirable image with less "depth of field," or a more diffused background. Take a look at the two pictures shown; the background is more diffused in the picture taken at f/2.8 than in the image taken at f/6.3.

Photo taken at f/2.8 & Photo taken at f/6.3


How to capture great landscape, portrait, and fast-action shots
using the correct f-stop
For nice landscape images you will want more depth of field, so you'll use a larger aperture number such as f/8, f/11, f/22, etc. You don't need as much light because you are already getting plenty of natural light outdoors.

For portraits or other shots where you want to have sharper focus on your subject by blurring the background, you'll want less depth of field and can use a smaller f-stop like f/1.4, f/2.8, f/5.6, etc.

For sports shots in arenas where there is less light and faster action, you will definitely desire a smaller f-stop, like f/1.4, to let in more light and allow faster, continuous shooting.

Photo taken with a 70-200mm 2.8 IS lens


Price considerations
One feature that will increase the price of a lens is fixed aperture. A zoom lens with a fixed aperture allows you to shoot at the highest aperture, at any focal length of the lens. This type of lens will be more expensive, but allows you to take better pictures in dark environments, as it allows more light into the lens without using a flash. You'll also gain more control of images in well-lit areas.

The limit to how wide a lens can be opened is called the maximum aperture. A lens with a wider maximum aperture lets in more light, having a significant impact on what types of photos you take. This type of lens is typically more expensive and an average photo hobbyist probably doesn't need a lens with a very wide maximum aperture. Bottom line: The wider a lens' aperture, the more it costs.

Less expensive zooms typically have a variable aperture, which means the more you zoom, the less light you get into the lens. For indoor shooting without a flash, this is not a good choice.

Some lenses run $2,000 to $3,000 and even more, but they are not right for everyone. It really depends on what types of photos you want to take. If you take a lot of photos of people posing outdoors, and do not shoot a lot of action shots, a less expensive lens will work just fine. For more creative photo options in darker-lit environments, or when you are shooting fast action, the more expensive lenses definitely offer results that surpass the less costly lenses.

Know what types of photos you'll be taking before you shop for a lens, and then buy a lens with a maximum aperture to suit your photography needs.

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