System: There are a variety of camera lenses to choose from. Most manufacturers have their own solution for how to mount lenses on their cameras, and usually, you can’t attach a lens from one system to another without using an adapter. Some camera manufacturers also use several different systems, so it’s important to choose wisely when buying a lens.
Here are some camera systems you will often encounter in the shops:
- Canon EF, Canon EF-M, Canon EF-S, Canon RF
- Nikon F, Nikon 1, Nikon Z
- Leica M, Leica R, Leica S, Leica T, Leica TL
- Sony A, Sony E
Sensor format: There are different types of sensors inside the camera. Depending on the type, these sensors have a certain size (such as full-format and APS-C). The lenses that work with your camera are specially designed to work optimally with that particular sensor size.
- Full frame: What is marked on the lens is what applies. 35 millimeters is 35 millimeter, 50 millimeter is 50 millimeter, and so on.
- APS-C is smaller than full-size and the focal length increases by 1.5x or 1.6x, depending on the system. Thus, 35 millimeter is practically closer to 50 millimeter, and a 100 millimeter becomes a 150 millimeter.
- Four Third: The extension factor is 2x which doubles the specified focal length of the Four Third camera lenses.
Lens Type: The lenses are classified according to their focal length:
- Fisheye: Extreme wide angle with a unique image effect
- Wide angle: 35 millimeters or less. Good for landscape, group photos and street photography.
- Normal: Approximately 50 millimeters
- Tele: From 75 millimeters upwards. Excellent for portraits and weddings.
- Telephoto: Zoom lens with a long zoom range, such as 18-105 millimeters.
- Macro: Lens with extreme close-up
Focal Length: The focal length is indicated in millimeters and refers to the magnification of the lens. The lower the number (shorter focal length) the more of the subject will fit into the image. A higher number (longer focal length) means you can get closer to the subject. A short focal length is good for landscape and indoor photography, while a long focal length is more suitable for sports and portraits.
The focal length indicated on the lens refers to the use of a camera with a full-frame sensor. If you use the same lens on a camera with a smaller sensor, such as an APS-C, you must add the crop factor.
Zoom or Fix: A zoom lens has moving lenses that allow you to change the focal length, while a fixed lens is locked to a specific focal length. The advantage of a zoom lens is that you get a greater scope to work with, but with the disadvantage that the image is often slightly worse than with a fixed lens. A fixed lens often has a larger aperture that emits more light for a softer background blur.
Aperture: The aperture controls the amount of light that enters through the objective lens. A large aperture increases the amount of light emitted and gives a softer background blur. A small aperture makes the background sharper, but reduces the light that reaches the camera's sensor. The aperture is often set between f / 1.2 (large aperture) and f / 22 (small aperture). The bigger the aperture the lens has, the bigger and heavier the lens is.
Weatherproofing: If the lens is used in tough environments that are dusty or humid, it’s good to have weatherproofing that protects the optics, as this reduces the risk of moisture damage or dust penetrating the glass elements in the lens. Weatherproofing also requires that the camera is weatherproof, for it to be completely sealed.
Stabilisation: Image stabilisation allows you to still take sharp pictures even in low light conditions when a slow shutter speed is required, or when using a long telephoto lens. The image stabiliser can be in the lens or in the camera body itself. If it’s in the camera body then it’s not necessary to have it in the lens as well, although in some cases you could use both together for an even better stabilising effect.
Bear in mind that manufacturers use different terms for lens stabilisation. Here are some character combinations you can look out for:
- Canon: IS - Image Stabilisation
- Nikon: VR - Vibration Reduction
- Olympus: IS - Image Stabilisation
- Panasonic: OIS - Optical Image Stabilisation
- Sigma: OS - Optical Stabilisation
- Sony: OSS - Optical Steady Shot
- Tamron: VC - Vibration Compensation
It’s also worth mentioning that stabilisation isn’t a good idea in every circumstance. If you place the camera on a tripod, you’ll need to turn off the stabilisation of both the lens and the camera. In addition, the manufacturers’ variants of stabilisation are not equally as good. The first generation VR technology from Nikon is not as effective as the newer, the VR II, while a Tamron lens can be better than both of those from Nikon.
Close focusing distance: Is the shortest distance between an object and the front of the lens before the camera can no longer focus properly. A macro lens has a very short focusing distance so you get really close. Regular lenses may in some instances have as much as 100 centimeters or more as their minimum focusing distance.
To get closer to an object, the lens can be tricked by using a close-up filter. It reduces the image quality a bit, but allows you to get closer to the object. You can also use extension tubes that are placed between the lens and the camera to increase the magnification.
Filter: A filter is mounted on the front of the lens to protect the front lens from scratches, and to give different effects. Lenses often cost many hundreds of pounds, and a single UV filter screwed in front of the lens reduces the risk of dirt, shock and scratches that can damage the lens. Be sure to select a high quality filter that doesn’t affect the quality of the image result. The size of the filter is given in millimeters and depends on the front lens diameter. Common sizes range from 37 millimeters up to 105 millimeters.
Here are some examples of common lense filters:
- UV filter: The most common filter that protects the lens and blocks UV rays.
- Skylight filter: Works like the UV filter, but reduces ultraviolet light to give a reddish-brown tone in the pictures.
- ND Filter: Reduces the amount of light to the camera sensor so you can shoot with larger apertures in bright light.
- Polarization filter: Reduces reflections from, for example water
Flare protection: Most lenses have a lens hood, either built-in, or attached to the front of the lens. The hood prevents random light that can create unwanted flares in the pictures. It is also an excellent protection if you drop the lens or hit it. If you add a good UV filter it reduces the risk of damage even more.