To determine the overall zoom ratio of the lens, simply divide the longest focal length by the shortest. So, for example, the Sigma mm F1. It is common practice to round to the nearest whole number or major fraction. So the mm F2. The zoom ratio only relates to the difference between the shortest and longest focal lengths, so the mm F All three of of these lenses offer the same maximum telephoto focal length, but the mm offers a much longer zoom range.
So, you can have a wide to short telephoto zoom lens with a higher overall zoom ratio than a telephoto to supertelephoto zoom lens. And the Sigma mm F3.
Zoom lenses also come in two main varieties: constant-aperture and variable-aperture. Each type has its strengths and purposes, depending on what is most critical to the photographer. When you look at the name of a zoom lens, if there is only a single aperture given, this is a constant aperture zoom lens.
If there are two F-stops named with a dash in between, this is a variable aperture zoom lens. Constant-Aperture zoom lenses keep the same maximum aperture throughout the entire focal range. So, for example, the mm F2. The key advantage of constant aperture zoom lenses is that you do not lose any light-gathering power as the focal length increases. This is helpful in challenging lighting situations, where the extra F-stops allow for faster shutter speeds. But constant-aperture zoom lenses are limited in total zoom range: the mm F4 is the highest zoom ratio constant-aperture zoom lens in our catalog.
And the demands of optical physics require a lot of big glass to make constant-aperture zooms, especially for the full-frame image circle.
Variable-aperture zoom lenses feature two F-stops in the name, indicating the maximum aperture at the shortest and longest focal distance. This means that the overall light-gathering power of the lens decreases as the focal length increases, leading to slower shutter speeds at longer focal lengths.
The benefits of this trade-off include more compact lens designs and higher zoom ratios. Whichever type of zoom lens it is, the Sigma lens designers strive to create the best possible lens, incorporating aspherical, SLD and FLD elements as necessary to best transmit the scene to sensor. The optimum optical formula varies depending on the focal lengths, and the goal is to always design the best-performing lens possible within the design parameters.
Many Sigma zoom lenses feature Optical Stabilizer, which is a floating lens group that counteracts slight camera movement during image capture—these lenses all have OS in the official lens name. Optical Stabilizer acts like an invisible tripod, minimizing slight camera movements during longer exposures. This can help keep handheld shots sharp at slower shutter speeds. The general rule of thumb is that OS can help keep images acceptably sharp for a few stops under the reciprocal of the focal length, so, the effective slowest shutter speed for sharp shots will change as you zoom in or out.
We take a long look at OS in this companion piece, if you want to l earn much more about how, when, and why to use OS when it is offered on a lens. Many of the larger Sigma lenses ship with tripod collars. These tripod collars are paired with the lens because the tripod collar indicates where the center of gravity of the lens and camera resides. You can stress the lens and camera mounts, and the center of gravity is under the tripod collar mounting point, which can lead to a tripod crashing over!
Zoom lenses are designed to offer the photographer a great deal of flexibility in composition and framing without ever having to change lenses, or even physical position, for that matter. All it takes is a quick twist of the zoom ring and the composition can go from the shortest focal distance to the longest for a very different take of the scene presented before your lens.
And many Sigma zoom lenses offer true macro capture at the telephoto end, for close-up capture of tiny objects, adding to the overall versatility. Of course, as you zoom in or out and recompose, the overall feel of the image can change dramatically, as a lens goes from a wide field of view to standard, or a standard field of view to supertelephoto.
Depth of field gets much more shallow as focal distance increases, even as telephoto compression diminishes the apparent relation between distant objects. The same scene can quickly be seen many different ways with a zoom lens. Zoom lens construction technology has come a very long way over the past forty years. And while it is still very typical for many zoom lenses to have some degree of field distortion at one end or the other of the zoom range as well as some slight vignetting at times, the overall image quality straight from the sensor of a modern zoom lens flat-out blows away the results of lenses from a few generations back.
These lenses for the smaller image circle are designated with DC in the official name. This is how it works, and this is how it is. On the shorter end of the focal lengths, it usually feels like APS-C is losing some of the wide-angle capabilities. But lenses like the pair of mm DC zooms and the mm F4. But this smaller sensor also means their is an apparent gain in focal length on the longer side of the zoom range.
This means that a mm focal length on an APS-C DSLR is more like a mm field of view and a mm focal length is like mm on a full-frame camera. For wildlife photographers, this sensor factor can make distant animals bigger in the frame. 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.
The mm is a telephoto lens that makes subjects appear more prominent in the frame. A mm lens lets you shoot subjects about 60 feet away from you to fill the frame. Since lenses can focus at infinity, you can use a mm lens to capture subjects beyond feet. A telephoto lens may not necessarily be a zoom lens, just like in the case of a mm lens. The mm focal length controls the field of view, which means this camera lens has a narrow angle of view at long distances.
Hence, if you want to include background and foreground elements, you need to move back until the camera sensor captures the actual size of the subject.
When talking about how far you can take photos with a mm lens, this refers to the ability to narrow your field, giving you a close-up perspective of the subject.
When it comes to mm lenses, the distance of how far you can take pictures refers to the magnification ratio. The shorter the focal length, the wider the angle of view and the lower the magnification.
There are two types of lenses-prime and zoom. Prime lenses have a fixed focal length and zoom lenses have variable focal lengths. Prime lenses tend to be more compact and lightweight than zoom lenses. This is an advantage when shooting in low light conditions as it will increase the possibility of hand holding the camera and freezing the subject without shake or blur caused by the longer exposures. Photographing using prime lenses with large apertures also means you can get a shallow depth of field which is useful for portraiture where you might want a softer or blurred background also known as bokeh.
Wide angle lenses are popular lenses for landscape photography , interiors, large group photos and when working in confined situations. Standard lenses are popular as they are closest to the angle of view we humans see. These lenses have minimal distortion, which can be flattering to the subject. They tend to use large apertures and allow a lot of light to enter the lens which makes them fast in low light conditions.
Standard lenses are the popular choice for a wide range of photography including portraiture, nature and low light situations where the photographer can not use a flash or is looking to capture the scene with available light.
Telephoto lenses between 70 — mm are very popular lenses for portraiture and product photography as well as nature and wildlife imagery. They allow the photographer to produce close crops on the subject. In the case of portraiture a telephoto allows the photographer to take the photo at a distance that does not intrude upon the subject. These lenses provide a good range for wildlife and sports photography where the photographer is limited as to how close they can get to the subject.
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