What’s the Difference Between Optical Zoom and Digital Zoom?

There are two basic ways of zooming in photography: optical zoom and digital zoom. Optical zoom leverages the physical change in a lens to adjust the distance between camera sensor and subject, whereas digital zoom uses magnification technology to enlarge an area of an image (thereby compromising the integrity of the picture by cutting down on the megapixels).

Optical zoom involves a physical camera lens movement, which changes the apparent closeness of the image subject by increasing the focal length. To zoom in, the lens moves away from the image sensor, and the scene is magnified. It is useful to think of digital zoom as photo-processing software built into your camera. By enlarging pixels in the center of the photo and cropping out the rest, digital zoom gives the appearance of magnifying the subject, while also lessening resolution and image quality.

While only film cameras allow for optical zoom, both film cameras and digital cameras (including point-and-shoot cameras, DSLRs, mirrorless cameras, and video cameras such as camcorders) have the possibility of using digital zoom, depending on the lens you’re using. There are two basic types of lenses: primes and zooms.

• Primes have a fixed focal length, making them faster and sharper.
• Zooms use a series of lenses to allow different focal lengths from a single lens, making them more flexible but not as fast.

Lenses are referred to by their focal lengths. If there is a single focal length listed, like 50mm, it’s a prime lens. If there are two numbers, like 15-35mm, it’s a zoom lens, listing the minimum and maximum focal lengths. Whether you’re using a film camera or a digital point-and-shoot, you won’t be able to use optical zoom with a prime lens, since you can’t change the focal length.

Not all zoom lenses have the same magnification capabilities. When selecting a zoom lens there are two main numbers to consider:

• Focal length. Focal length has to do with the apparent closeness of the subject and is measured in millimeters. At the two ends of the focal-length spectrum are telephoto lenses and wide-angle lenses. A lens with a focal length of 60mm or longer is called a telephoto lens. The longer the focal length, the narrower the angle of view, and the more magnification power the lens has. Telephoto is the type of lens you want to use when you’re shooting something far away, such as wildlife. Wide-angle lenses (35mm and below) have a shorter focal length and are popular for photographing landscapes. When you’re zooming in with an optical zoom lens, you’re going from the wide-angle end of the lens to the telephoto end.
• Zoom ratio. How far you can zoom in or out depends on your maximum and minimum focal lengths. The ratio of these two lengths is called the zoom ratio, and it’s a number you’ll often see advertised with compact cameras expressed as a number and the letter X. Lenses with a very high zoom ratio are sometimes called superzoom lenses. Keep in mind that a large zoom ratio doesn’t necessarily mean you can take extreme close-up photos, since the zoom ratio is more of a measure of a lens’s versatility than its magnification capabilities.

Even though optical zoom is about lenses, there is some digital technology that influences your optical zoom. Some digital cameras have a zoom feature called smooth zoom, allowing you to get a partial zoom anywhere between focal lengths, whereas others have stops at specific positions along the lens. Long zoom lenses can sometimes have problems with camera shake, which digital cameras attempt to fix with image stabilization.

If you’re looking to take high-resolution photographs, stick with optical zoom, which keeps image resolution the same no matter how far you zoom in. Most professional photographers prefer not to use digital zoom, instead opting to shoot in RAW and enlarge and crop later, in photo-editing software.

With digital zoom, how far you can zoom in depends on your camera’s megapixels, or the number of pixels that make up an image and determine resolution. Intelligent zoom is a newer type of digital zoom that decreases image size, so that digitally zoomed-in images appear to be of higher quality. In-camera digital zoom can be useful, however, in that it allows you to see farther away in the moment, so that you have a better idea of what you’re photographing, especially when you’re working with moving subjects. It’s also typically the only type of zoom available when using a smartphone camera, whereas optical zoom is the only type of zoom available to film cameras.

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