Zoom lens how does it work

Click here to download it for free. The lenses that you use on your camera can make a huge difference in the quality and style of your images. Good glass makes a lot of difference! But there is a huge array of lenses out there and it can seem impossible to decide which one will best suit your needs.

A zoom lens is a lens that covers a range of focal lengths e. To understand a lens, you need to first understand focal length. So, what is focal length? The focal length is the distance in millimeters between your lens and the image recorded on your sensor when the lens is focused at infinity.

Infinity refers to the farthest possible distance that can be seen. It is this distance that essentially determines your angle of view i. Camera lenses are classified by their focal lengths, starting from a standard lens that gives roughly the same perspective as the human eye. This is the 50mm lens, although lenses of around 20mm to each side of 50mm are also classified as standard. Lenses with less focal length are wide-angle lenses, as they have a wider angle of view, whereas those with a greater focal length are telephotos and have a narrower angle of view.

A zoom lens allows a photographer to adjust the focal length of the lens within its specific range i. The focal length range of a zoom lens will be clearly marked on the side of its barrel. Photograph by Markus Spiske. A prime lens, on the other hand, has a fixed focal length e. Both types of lens have their advantages and disadvantages.

The main advantage of a zoom lens is the fact that you can cover a range of focal lengths and can change the angle of view quickly, without needing to change your lens. Zoom lenses are invaluable for events, weddings, and sports, where you are likely to need to zoom in and out to recompose a scene quickly. You can get one zoom lens to do the job of several prime lenses.

You might be wondering why anyone would bother buying a prime lens, but they do have several advantages. Firstly, a prime lens will usually be sharper than a zoom lens.

Secondly, a prime lens always has one fixed maximum aperture e. Most zoom lenses will have a variable maximum aperture e. Key Lesson: You can buy zoom lenses with a fixed aperture throughout their range e.

And when it comes to full-frame lenses on APS-C DSLRs, the smaller image circle means that the image is captured with incredible sharpness from the center section of the lens. Many Sigma zoom lenses offer a macro capture mode at the longest focal length at magnification ratios between one-third and one-half life sized reproduction. When a Sigma zoom lens has Macro in the official name, it means that it has a maximum magnification ratio of or greater.

This means that at the closest focusing distance, a one inch object will be rendered as one-third of an inch.

For many photographers first exploring macro capture, this a great way to get comfortable with the nuances of macro photography. At very close focusing distances, all motion is amplified. For example, a bit of jittery camera movement, and the slight swaying of a flower can mean the difference between having that ladybug perfectly in focus or having the subject drift out of the sharpness zone.

Macro takes practice, and if you crave higher magnification than is offered at the far end of a the zoom, Sigma offers a line of pro-caliber prime macros offer true life-sized magnification for even more close-up details. As of April , Sigma offers two mirrorless-exclusive zoom lenses, the mm F2. Learn much more about which Sigma lenses fit which camera systems here. A single zoom lens such as the mm can cover wide-angle to telephoto, plus macro in a single lens, when traveling light with maximum versatility is the demand.

Or a zoom lens like the mm F2. The Sigma mm F1. The pair of Sigma mm F The Sigma mm F2. Check out the full lineup here. In April , it was revised to include updated product information and links, mirrorless zoom lens information etc.

Based in Central Jersey, Jack's go-to photography spots are backroads and beaches of his home state. He loves to travel far and wide with his wife and daughter, visiting national parks, museums, tropical islands and more along the way. Zoom is also commonly confused with how close a lens can bring a subject. The zoom number, like, only shows the range from the widest to narrowest angle of view for that lens.

Zoom is a good indicator of flexibility, then, but not how close you can get with that lens. For that, you need the focal length, like m, 1m, etc. In point-and-shoot cameras, it s more common for manufacturers to advertise the zoom rating of a lens ,, etc. If a lens has a single focal length number, e. Save my name, email, and website in this browser for the next time I comment.

Notify me of follow-up comments by email. Notify me of new posts by email. What is a Zoom Lens? Why and When to Choose a Zoom Lens? Back to sigmaphoto. Home What is a Zoom Lens? Fall leaves seen through the Sigma mm F1.

Same scene, seen through the same lens, this time fully zoomed to 35mm. Notice how the background is more abstract, even with the same F4. The result is that this lens consists of 11 optical groups or 22 lens surfaces which need to be coated or multicoated in order to maintain proper light transmission, color balance, and to prevent internal reflections or lens flare.

The mechanical movement of the optics within this zoom lens can be broken down into three independently moving groups of optical elements and one stationary group of optical elements. Some zoom lenses actually move all four optical groups when the lens is zoomed.

These four optical groups from front to back are: the focus group , the variator group , the compensator group , and the master group. We have color shaded the CAD drawing to indicate the internal mechanical housings which hold the optics for each of these four optical groups. Nearly every zoom lens consists of these four types of optical groups. So, what do these four optical groups do?

The front or top group of lens elements is called the focus group. The focus group moves forward or backward as necessary for focusing the lens.

In a conventional telephoto zoom such as the SP , this focus group does not move when the lens is zoomed. It only moves when the zoom's focus collar is rotated. Some telephoto zooms feature optical designs wherein the length of the lens increases as the lens is zoomed to its longest telephoto position.

The front focus groups in these lenses move not only when focusing but also when zooming these lenses. The variator group of lens elements, like its name implies, varies the magnification power of the focus group. The variator group is the moving group which is mostly responsible for changing the focal length of a zoom lens when it is zoomed. Note that the variator group alone isn't enough to achieve a true zoom function and maintain focus. Many readers may recall the varifocal lenses which were introduced in the late s.

These lenses were not true zooms because the user had to refocus the lens after "zooming". Something else, optically, has to be used to maintain proper focus when zooming a true zoom lens. This "something else" is the compensator group of lens elements. True zoom lenses have a compensator group which moves in the same direction but at a different rate compared to the focus group. The compensator group's sole purpose is to maintain correct focus whenever the zoom lens is zoomed.

We mentioned that the variator group is mostly responsible for changing the focal length of a zoom lens when its is zoomed. The compensator group is also partly responsible for changing the focal length of the lens when it is zoomed. The variator and compensator groups work together to create the change in focal length when the lens is zoomed, and the compensator group also assures that the lens remains in focus while being zoomed.

They are also great if you need to blur the backgrounds. With their low aperture numbers, you can get narrow depths of field.

But they are usually more expensive. Once you know the focal length, zoom range and aperture you would like to have, it is time to check what the market has to offer. At this point, you should check your budget. Lenses are a real temptation for photographers, but they can be costly. It is easy to end up spending much more than you have to.

It is vital to set the limit of money you can invest in your lens. A way of saving money is to buy lenses from another brand instead than your camera brand.

When choosing a brand , you need to make sure that the lens is compatible with your camera model. The image quality should also be good enough for your purpose. You should check if the lens offers autofocus.

To keep in your budget, you might need to concede the zoom range or the aperture values you wanted a bit. Evaluate if making changes will be right for you or not. You can wait until you save the money, buy second hand or rent the lens for the days you need it.

A zoom lens is an optical apparatus that contains several lenses and glass elements. The focal point and angle of view can be adjusted within a given range. Zoom lenses offer the photographer high versatility without needing to change the lens.

Optical zoom is a technology that magnifies the size of an image without getting closer to the subject. It is based on a system that changes the position of the lens in relation to the camera sensor to extend the focal length. A camera lens works by converging light rays to one point of the camera sensor the focal point to create an image. Lenses are built with the correct combination of several lenses. This combination helps to increase sharpness and avoid chromatic aberration.

Telephoto lenses are for any situation in which the subject of the image is far from the camera. Wildlife and sports photography are good examples. There are a lot of zoom lens types in the market. To decide which one to buy, you need to consider your budget and the style of photography you like. Remember that a zoom lens also has disadvantages, especially in low lighting conditions. Leaving your camera on its default settings will produce blurry results.

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