All lenses produce a circular image on the camera sensor or film, and this ‘image circle’ must be at least large enough to cover the full film/sensor area. Different lenses designed for different sensor sizes and formats have different-sized image circles. Lenses designed for APS-C format cameras, for example, have a smaller image circle than […]
The lens is a fundamental part of any camera. It's what creates the image on the camera sensor (or film). Some cameras have a fixed, non-removable lens while others offer interchangeable lenses. Your choice of lens has a major impact on the appearance of your pictures, including the lens's focal length (angle of view) and its aperture setting (which you may or may not be able to adjust). At a simple level the lens is just the thing on the front of the camera, but on a more advanced level lenses open up a whole world of photographic choices, buying decisions and technical comparisons.
Here's a selection of further lens-related topics
Camera lenses used complex configurations of different optical elements, often cemented or fixed together in ‘groups’. Lens groups may be designed to counteract common optical aberrations and you may have autofocus ‘groups’ and zoom groups. Lens elements and groups often move relative to each other in complex ways as the focus and zoom settings are […]
STM stands for stepper motor lenses, a new type of autofocus motor used by Canon in some of its lenses. Stepper motors offer fast, precise and quiet focus adjustments, so these lenses are well suited both to regular stills photography and to video, where autofocus noise can be picked up very easily by the camera’s […]
The lens is a fundamental part of any camera. It’s what creates the image on the camera sensor (or film). Some cameras have a fixed, non-removable lens while others offer interchangeable lenses. Your choice of lens has a major impact on the appearance of your pictures, including the lens’s focal length (angle of view) and […]
Camera lenses are made up of not just one single lens but many different lens ‘elements’, sometimes cemented or fixed together in ‘groups’. A comparatively simple prime (non zoom) lens may have 6-7 elements while a complex zoom lens might have 17 or more. The different lens elements are needed to compensate for a variety […]
Aspherical lenses offer better correction for many common lens aberrations than regular spherical lenses. Lenses with a spherical profile are easier to grind into the correct shape, but aspherical lenses have a more complex profile that’s more difficult and more expensive to make. Many modern lenses use moulded aspherical elements instead to get round this. […]
Reproduction ratio is a term used in macro photography to indicate the degree of magnification. A ratio of 1:1 is usually considered the minimum for ‘true’ macro photography. This means that an object is reproduced at exactly the same size on the sensor or film surface as it is in real life. If the first […]
An apochromatic (APO) lens is designed to offer improved correction of chromatic aberration and spherical aberration using specialised materials and combinations of lens elements. It’s a selling point for lenses, though only indicates the lens design used and isn’t really a guarantee of good performance on its own.
A system introduced by Nikon for some of its lenses where the lens aperture diaphragm in the lens is controlled electromagnetically rather than by the traditional mechanical linking. This gives more accurate and consistent exposures, especially during continuous shooting, where the lens diaphragm may be adjusted many times a second.
A lens with a fixed focal length, as opposed to a zoom lens. Prime lenses are more restrictive, but they tend to produce better optical quality with fewer aberrations and offer a wider maximum aperture. They also tend to be lighter and smaller, and many photographers find that having to change position to get the […]
A lens which can be adjusted to give a range of different focal lengths. Most lenses in use today are zooms because they’re so much more versatile than fixed focal length (prime) lenses – you can adjust the framing without having to change the camera position. The disadvantages of zoom lenses are increased distortion and […]
The difference in magnification offered by a zoom lens and its widest and longest focal lengths. The average kit lens has a zoom range of 3x, so at full zoom objects appear 3x larger than they do when you’re zoomed right out. The Nikon P900 has a record-breaking 83x zoom.
A zoom function produced by changing the magnification of the lens rather than by simply blowing up a central part of the image (digital zoom). Makers will always specify optical zoom and digital zoom separately in their specifications.
Image stabiliser which moves physical elements within the lens, or the sensor itself, to keep the image steady during the exposure. This is superior to ‘digital stabilizers’ which use image processing techniques to reduce blur, but which also lead to a loss in quality.
The maximum light-gathering power of a lens and a major selling point.It lets you use faster shutter speeds or lower ISO settings in poor light.This lens has a maximum aperture of 1:2.8. This is the same as f/2.8 – different makers use slightly different terminology.
Lens hoods can reduce lens flare and improve contrast when there’s a bright light source just outside the edge of the frame, but they won’t help if the sun, for example, is in the frame. Lens hoods are usually ‘petal’ types that allow for the fact the image frame is rectangular.
Lenses aren’t perfect – they all have optical aberrations of one sort or another. Now, though, many software applications have lens correction to
A switch found on some telephoto and macro lenses to restrict the autofocus to a specific range. This speeds up the autofocus for situations where you know you won’t need the lens’s full focus range.
This tells you a lens’s magnification or angle of view (it’s the same thing really) and it’s quoted in millimetres. Sometimes the makers quote actual millimetres and sometimes they quote the ‘effective’ focal length, which is what the lens would be equivalent to if it was a 35mm camera.
This is a fine screw thread cut into the front of almost all DSLR and mirrorless camera lenses. This is where you screw in glass filters, or the adaptor rings for square filter holders. The size of the filter thread varies, so make sure you buy filters or adaptors the right size for your lens.