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The Lens Explained: Telephoto vs. Wide-Angle

Talking to a typical camera geek can be like trying to communicate with someone in a secret code. Sure, you understand "say cheese" and "smile for the birdie," but when you're on the hunt for new camera gear, you need to be able speak their language. That's why Gizmodo has teamed up with Tamron to bring you The Lens Explained, a series that breaks down everything you need to know about camera lenses.

Today's post examines the differences between wide-angle and telephoto lenses, starting with a few key concepts:


Focal length

Simply put, focal length is the distance in millimeters between the lens and the censor when the camera is focused on a subject at infinity. To focus on something closer than infinity (which is probably what you're aiming to do), the lens is moved farther away from the film using the focus ring. So, in theory, a 200mm telephoto lens (you can discern that it's telephoto because the numerical value of the focal length is higher than normal human vision) would be 200mm long when fully extended. (Telephoto lenses don't actually extend this way—camera lenses are made up of many individual glass lenses, which make them function as if they're much longer than they actually are.

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If the numerical value of a focal length is lower than normal, then your lens will render negative magnification, resulting in a wide angle. So, if you're standing really close to a pretty butterfly and you want to capture the dewdrops on her wings just so—a wide-angle lens is the way to go.

Camera lenses that carry a range of focal lengths (for example, 18-200mm) can go from telephoto to wide-angle, so are considered zoom lenses.

Perspective

Photographic lenses create a visual effect which makes nearby objects appear larger while distant objects look smaller. Pretty simple stuff, right? Well, when a wide-angle lens is used, an amplified version of this effect takes place. As the focal length becomes shorter, the perspective difference expands, making a close subject appear that much bigger and remote objects even smaller—this is called exaggerated perspective.

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However, when a telephoto lens is used and focal lengths become longer, less difference is distinguishable between close and distant subjects. This effect is called compressed perspective, and makes it appear as if objects are closer, regardless of the distance between them.

Depth of Field

When a camera is focused on a subject, there are spaces directly in front of and behind the main subject where details still appear acceptably sharp. This amount of distance is referred to as the depth of field. The area can be widened by closing the lens aperture, giving it a "deep depth of field," or narrowed to make the amount of space shallower. Wide-angle lenses deliver a deeper depth of field than is delivered by telephoto lenses.

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Not terribly painful, right? And now you'll be able to understand this next part: the Tamron 18-270mm lens is a super powerful, all-in-one 15X zoom lens. It's made for use with Canon, Nikon, and Sony APS-C size DSLR cameras, and has won two major awards: the EISA Best Product 2011-2012 and the Japan Camera Grand Prix 2011. Weighing just 15.9 ounces and measuring 3.8 inches in length, the impressively compact lens features Vibration Compensation (Tamron's proprietary image stabilization) and a Piezo Drive (don't worry, you'll find out what this does next time).

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Head here now for a closer look at all of the features of the Tamron 18-270mm lens.

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