What’s important besides picture quality? | |
| In the first installment of a Roadmap for purchasing a lens, we focused on you: What subjects do you like to photograph? How much equipment do you carry? How much money do you have for it? In the second installment (What’s the best lens for me?), you can choose the lens type that best suits your needs. Do you do sports photography, macro photography, street photography or wedding photography? On holiday, you might take a different type of lens along. Now we come to the lens properties and concepts that you’ll run across when you want to buy a lens. |  |
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Choose the right lens mount | |
There are also brands like Sigma and Tamron, that make lenses in different camera mounts. They offer lenses for sale with a Canon, Sony, Sigma, Nikon and sometimes a Pentax mount. Olympus and Panasonic cameras have the same (micro-43) mount, allowing you to use micro-43 lenses both on Olympus and Panasonic cameras. Sometimes the lens mount depends on the sensor size, for example, Canon SLRs with a full-format/full-frame/FX sensor and cameras with a smaller APS-C/DX sensor. Lenses made for a full-frame camera always fit on a camera with an APS-C or DX sensor. Vice versa is not always the case. A Canon EF-S lens, designed for cameras with an APS-C sensor, does not fit on a camera with a full-frame sensor like the Canon 6D or Canon 5D MK3. Nikon DX lenses fit on a Nikon FX camera. If you put a Nikon DX lens on a Nikon FX camera, then the camera uses only a part of the sensor and the field is automatically adjusted. Lenses from other brands, which are designed for a Canon camera with an APS-C sensor usually have an EF mount. That means that those lenses may fit on a Canon camera with a full-frame sensor, but that the edges of the image will be black. At the photo store, they’ll make sure that you have a lens with the right mount. If you buy a lens over the internet, then you have to pay attention yourself.
Secret language for lenses: Many brands indicate in the type-designation for which sensor a lens is designed: | |
Lenses for a camera with a full-format sensor
| Lenses for an APS-C camera
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Focal length and sensor size | |
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| The focal length or the zoom range of a lens determine whether you show something up close, or just give an overview. These shots are taken from the same position with—converted to full-frame—a 16 mm Fisheye lens, a 28 mm lens, a 100 mm lens and a 600 mm super telephoto lens. | |
The focal length of a lens, which is expressed in millimeters, help determine what’s in the picture:
Other factors that determine how much appears on a photograph, include the distance at which a picture is taken and the size of the sensor. Below you can see the image that is captured by the sensor if you use the same 50 mm lens on a camera with a full-frame sensor, an APS-C sensor, or via an adapter on a camera with a micro-43 sensor or a Nikon 1 sensor. The smaller the sensor, the more light falls next to the sensor. The image of the dark mill is the same size on all sensors. If you want to view the shots full-screen on a monitor, then you need to enlarge a shot made with a APS-C sensor by 1.5x, an image with a micro-43 sensor, 2x; and a shot made with a Nikon 1 camera, 3.7x. With the smaller sensors, you have an image outcropping made from the whole picture. The factor by which the image has to be enlarged to look like a shot made with a full-frame sensor is called the crop-factor. | |
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Why a smaller sensor gives more depth of field | |
If you want to capture on a camera with a smaller sensor as much as with a full-frame sensor, then you should use a shorter focal length on the camera with the smaller sensor. The shorter the focal length, the greater the depth of field. Therefore, a picture taken with a compact camera always has a big depth of field. Although the manufacturers of compact cameras often report focal lengths that have been converted to a camera with a full-frame sensor, compact cameras in reality have lenses with a very short focal length. With system cameras, the differences are smaller. A 18-55 mm standard lens on a camera with an APS-C sensor you use for the same applications as a 28-85 (or 24-70) mm lens on a camera with a full-frame sensor. There isn’t as much on the photos, but the depth of field of the shot made with the APS-C camera is larger.
On a picture taken with a 50 mm lens on a camera with a full-frame sensor, the subject is depicted the same as on a picture taken with a 25 mm lens on a micro-43 camera. We’ve illustrated that in the following picture of 4 sensor/lens combinations that match in terms of field of view. Do you notice that the micro-43 camera has a different ratio? Most cameras have an aspect ratio of 2:3. A micro-43 has a 4:3 aspect ratio, giving you more air in the following example, in the shot made with the micro-43 lens. | |
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Why focal lengths of lenses on system cameras are converted to full frame | |
A 25 mm lens on a camera with a full-frame sensor is a wide angle lens. A 25 mm lens on a micro-43 camera is a standard lens. A 25 mm lens on a Nikon 1 camera is a short telephoto lens. Because the field of view of a lens with a certain focal length depending on the sensor size gives a different picture, then, it’s not enough to know the focal length to know what type of lens it is. It is obvious to use the field of view of a lens in place of the focal length, because that way you describe the type of lens in one number. But there are disadvantages too. Do you know which lens type has a horizontal field of view of 39° 36′? I’ll help: this is equivalent to a diagonal field of view of 46° 48′. Working with a field of view is more difficult than working with a focal length. If you choose on the same camera a lens with twice the focal length, then you bring the image twice as close to you. That unfortunately doesn’t apply for the field of view: that is not twice as small. It’s thus attractive to continue working with a focal length. In addition, most photographers are used to working with the focal lengths of lenses on full-frame cameras. Therefore photographers recalculate the focal lengths on other sensors to the 35 mm equivalent (mm @ ff). To divide all lenses independent of the sensor into different application areas, we also calculate on CameraStuffReview the focal lengths to the focal lengths equivalent on a camera with a full-frame sensor ([email protected]). | |
Important for indoor photography: Brightness | |
| The aperture of a lens controls, along with the shutter, the amount of light hitting the sensor. The biggest opening of an aperture is a good measure for the brightness of a lens. Lenses with a high brightness (smaller than f/2.8) are more expensive to make, but offer a bright viewfinder image and are suitable for applications. If you want to isolate a subject from the background, then it’s also wise to buy a lens with a bright lens. With zoom lenses, the brightness varies sometimes across the zoom range, and that’s indicated by the starting value and ending value: f/3.5-f/5.6. More expensive, larger and heavier zoom lenses have a constant brightness. | Secret language for special types of glass:
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Build quality of a lens | |
| The materials that are used to create a lens determine to a large extent the build quality and the cost of a lens. Not everyone has a lens that is built like a tank. For many, a low weight is much more attractive. The same applies for extra sealing against dust and moisture. The additional cost for such lenses is only interesting for photographers who have to work under extreme conditions. In the past, lenses were always equipped with a metal lens mount. Today, some inexpensive and light lenses are equipped with a plastic lens mount. The question is whether the build quality matters much. With some zoom lenses, the zoom ring runs so smoothly that after a while the lens will automatically zoom out if you put it vertically. That is bothersome, because the lens does not stay on the focal length that you’ve chosen. On some zoom lenses there’s a switch that allows you to lock the zoom lens during transportation. | Secret language for Nikon lenses:
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Auto focus | |
For some of the advanced photographers, who more often focus manually, with the lens choice, there are a few points to consider when it comes to focusing. In some, usually more expensive, lenses you have the freedom to choose between manual and auto focus without having to flip a switch. That works much faster: without taking your eye off your subject, you can overrule the auto focus by turning the focus ring. |  |
Even more secret language for lenses: Some lenses have AF marked in the lens name, but that is actually unnecessary. Today practically all lenses are AF-lenses. A few lenses are designated in the type-label with the indication MF. With such a lens, you can only focus manually. A modern AF motor is called USM (Ultrasonic Motor) by Canon, SW (Sonic Wave) by Nikon, HSM (Hypersonic Motor) by Sigma and PZD (Piezo Drive) by Tamron. Many lenses have a focus motor in which a small lens element in the lens is moved, instead of the large, heavy front lens. Some of these lenses are indicated in the type designation with IF. Canon lenses with an ultrasonic AF motor (USM) are less suitable for video than the Canon lenses with a stepper moter (STM). STM lenses are quieter and faster focusing for video. | |
Manual focusing | |
| If you’re focusing manually, then you want to do thatwith an easy-to-reach, sufficiently broad focus ring, which runs smoothly and is accurate. Some of the cheaper lenses have such a narrow focus ring that it’s fair to say that they are not designed to focus manually. It may be wrong, but you easily grab wrong, and it doesn’t work. The flexibility of a focus ring or zoom ring is hard to express in a figure. However, in general, the more expensive the lens, the nicer the manual focusing. The friction of the focusing ring is so well adjusted that the ring has no play, doesn’t inadvertently twist and yet very runs smoothly. If you’re in the photo store trying out an expensive and an inexpensive lens right next to each other, then you’ll notice the difference. | |
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Interchangeable lenses and video | |
| If you’re making video footage, then it’s important that the focus motor of a lens is silent. The less glass the AF motor has to move, the quieter and faster that can be done. Therefore, most lenses for compact system cameras (Nikon 1, micro-43) are as fast and quiet as possible. For SLRs more and more lenses are on the market with internal focusing (IF) or a stepper motor. Such lenses are a good choice for video. There are a few zoom lenses on the market with a motor zoom. With these zoom lenses, such as the two Powerzooms (PZ) by Panasonic, you can zoom in or out while operating your camera remotely. | |
Image Stabilization | |
In low-light situations, thanks to built-in image stabilization you can still shoot without flash or tripod without fear of motion blur. Sometimes lenses with image stabilization are much more expensive than the version without image stabilization. In theory, a lens is also made heavier and larger by built-in image stabilization. In practice though, that’s not such a big issue. The cheapest kit lenses for starters today are often equipped with built-in image stabilization. Our reviews shows that that image stabilization does its job very well. | |
Secret language for lenses: The name for image stabilization varies by brand, but the effect does not:
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Some (Pentax, Samsung, Olympus and older Sony) cameras have built-in image stabilization. In particular, Olympus cameras have a very good built-in image stabilization. If you have such a camera, then built-in image stabilization when choosing a lens is less important. In all other cases—and for the Olympus camera owner who may in the future ever want to buy a camera without built-in image stabilization—built-in image stabilization is a major plus. When the camera pulls in the direction of a moving subject, then you don’t want the image stabilization trying to compensate for your conscious movement. Some lenses are automatically switched to another form of image stabilization, where the movement is only corrected in 1 direction. There are also lenses with a switch for the different forms of image stabilization. | |
Extras | |
| So what can you look at if you have your eye on a few lenses with more or less the same build and image quality? Then look at the extras that you get when buying some lenses. Some manufacturers give a beautiful matching pouch or case to house your precious treasure when you buy a lens. The length of the warranty period may vary. If you buy a lens without a lens hood and you buy the official lens hood at a later stage, then you’re a few dozen euros poorer. Take the price of the lens hood into the price comparison if that’s not included. |  |
When purchasing some heavy telephoto lenses (like the Canon 70-200 mm f/2.8), you’ll get a tripod collar. If you buy a Canon 70-200 mm f/4 zoom lens, then this is not the case. This explains in part the higher price of the brighter telephoto zoom. If you’re interested in a fisheye lens or in an extreme wide-angle lens, look at the specifications to confirm whether it is possible, if you like to use filters. Usually this is not possible. | Canon geheimtaal voor lenzen:
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| In our reviews, we describe whether the front lens rotates when you zooms or focus. In principle, that doesn’t matter. But if you used a gradient filter that is darker on top than on the bottom, then that is annoying. As a last point of attention, we give the filter size: If you buy a lens of the same filter size as a lens that you already have, then you can use the same filters on multiple lenses. Good polarization filters, for example, are expensive. Thus you can save money by paying attention to the filter size. | |
Tip: If you’re buying a lens for the camera you have for the first time, then pay attention. Every brand has its own camera mount, which only lenses fit with the same mount. A Canon lens (with a EF mount or a EF-S mount) will not fit on a Nikon SLR camera (Nikon F mount).
Tip: Do you now have a camera with an APS-S sensor, but you’re planning to buy a camera with a full-frame sensor in the future? Choose a lens that also fits on a camera with a full-frame sensor. That saves you money later, when that camera with a full-frame sensor comes along.