If you are in the market for a camera, especially a compact or fixed lens point and shoot camera, you’ve probably come across the terms optical and digital zoom. But what do these phrases mean? Is one type of zoom better than another? Camera manufacturers use all kinds of jargon to entice you to buy their products, but the important fundamentals are actually quite straightforward. Hopefully, after reading this article, you will be better informed on all things zoom.
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What Is Zoom?
In photographic terms, to “zoom in” means to make your subject larger in the frame, without actually moving forward yourself (instead, zooming on your lens). On the other hand, to “zoom out” means to go the other way, or to make your subject smaller in the frame. Zoom lenses allow you to do this and are incredibly convenient. They allow you to change focal lengths without actually using a different lens entirely.
On a DSLR or mirrorless camera, zooming is done by either rotating a ring on your lens, or by pushing and pulling on the barrel of the lens. In the case of most compact cameras, zooming is done by turning a dial on the top of the camera. These motions adjust the focal length of the lens, allowing you to magnify the scene.
However, not all zoom is equal!
Optical Zoom
With optical zoom, the glass elements inside the lens move to increase or decrease the focal length of the lens. Any time you hear someone mention a “zoom lens,” they are referring to a lens with the ability to change focal length by moving its glass elements.
Optical zoom is the ideal way to zoom in while retaining as much image quality as possible. However, some cameras also advertise something called “digital zoom.” Do not confuse optical and digital zoom. They are not the same thing, as you will see in a moment.
One example of a lens with an optical zoom is the Fujifilm XF 100-400mm f/4.5-5.6 R LM OIS WR lens. This lens zooms from 100mm (a moderate telephoto) to 400mm (a strong telephoto). Notice how the barrel of the Fujifilm lens extends when the lens is zoomed in. Some zoom lenses do this internally, so you do not see the barrel lengthen, such as Nikon’s and Canon’s 70-200mm f/2.8 lenses.
Digital Zoom
Digital zoom is created in-camera, not using the lens’s optics. To do this, the camera crops into the centre of the image. Then the cropped capture is digitally enlarged back up to size by adding pixels to the picture. During this process, image quality can suffer drastically!
My iPhone 8 Plus has two lenses. One has a 28 mm focal length (in 35 mm equivalent terms), and the other is 56 mm. It also has a 10X digital zoom. Here are three images. They are taken at 28mm, 56mm (2X optical zoom), and 280mm (10X digital zoom) respectively. Notice how the image quality is severely compromised using the long digital zoom.
There is rarely a good reason to go beyond your lens’s optics and start using a camera’s digital zoom. Instead of letting the camera crop your photo for you, just crop it yourself on your computer. Even if you crop away half the picture, you will still have enough resolution to print 4×6 photos and more than enough size to post your images digitally on social media.
In those few cases when you need to get even tighter or want to make large prints, software programs will do a much better job of upsizing your image than the digital zoom on the camera. On1 Resize, Alien Skin’s Blow Up, and freeware by Gimp and Irfan View all do a good job at upsizing photographs.
The takeaway here is to ignore the digital zoom claims from camera manufacturers. If reach and image quality are essential to you, concentrate on optical zoom only.
Zoom Power
There are two ways you will see the power of a zoom lens quoted. One method is by the lens’s focal length, and the other is by its zoom ratio. While focal length is used almost exclusively in the DSLR and mirrorless world, the zoom ratio is much more common when looking at point and shoot cameras. However, focal length and zoom ratio apply to both types of camera lenses.
Focal length describes the angle of view of the lens. The longer the focal length, the narrower the angle of view, and the more magnification you will experience. For example, Nikon’s 200-500mm f/5.6E ED VR Lens is an excellent lens for wildlife photographers. It allows you to get very close to your subject when zoomed to 500mm.
With compact cameras, the zoom ratio is used to indicate the power of the lens, rather than the focal length. You will see it listed in the advertising with an X, such as 3X or 10X. The zoom ratio is the value of the longest focal length of the lens divided by its shortest focal length. So, the zoom ratio for Nikon’s 200-500mm lens above is 500mm÷200mm, or 2.5X.
The X Factor
Let’s look more closely at zoom ratio (X factor), as it can be a bit confusing. For example, consider Nikon’s 28-300mm f/3.5-5.6G ED VR Lens. Although its reach isn’t nearly as far as the 200-500mm lens, its zoom ratio is much bigger. The 28-300mm lens has a zoom ratio of 300mm÷28mm, or 10.7X! So, the zoom ratio does not indicate how close you can get to your subject. A higher number simply indicates that there is a bigger range between the wide and telephoto end of the lens.
Cameras with the same zoom ratio do not necessarily have the same focal lengths! Let’s look at two more examples. Canon’s PowerShot SX740 and Nikon’s Coolpix B500 both have 40X optical zooms. However, when you dig a little deeper into their specifications, you find that the focal length (in equivalent full-frame terms) of the PowerShot is 24-960mm, while the Coolpix is 22.5-900 mm. In other words, if reach is of the utmost importance to you, Canon’s PowerShot will be more attractive to you. On the other hand, if you are a landscape photographer, and want to work with wider angles, the Coolpix will be more suited to your shooting style.
Conclusion
Using a zoom lens is a great way to get in close to the action when physically getting close is impossible. However, remember that optical and digital zoom are not created equal. If you have a point and shoot camera and want to zoom in tight, use the optical zoom. Although zooming in closer is tempting, the results using digital zoom will be disappointing, and you are better off just cropping instead.
If you are buying a new compact camera, do not use digital zoom to compare models. Instead, focus on the optical zoom specifications and – most importantly – the focal lengths of the lenses. Once you have your new toy, to prevent it from accidentally zooming past its optical limits, make sure you turn off the digital zoom feature in the menu.