An SLR lens includes many glass elements arranged in groups.
A single-lens reflex (SLR) camera includes a mirror system that allows you to see accurately what the camera will record. By viewing through the lens, you can control the focus on certain areas of the image. An SLR camera system allows you to interchange your camera's lenses to suit your photography needs. Unlike compact cameras with a fixed lens, the SLR camera can give you a range of views from wide-angle to telephoto according to the focal length of the lens.
Viewing the Light
One SLR lens consists of multiple lenses or glass elements of different shapes that help produce a clear image. The light rays enter the front of the lens, travel through the lens barrel and reach a small reflex mirror in the camera body. This angled mirror reflects the light up to the pentaprism near the roof of the camera body. The five-sided glass prism allows the image seen by the lens to be viewed through the viewfinder at the back of the camera. This pentaprism lies in the optical path between the reflex mirror and viewfinder.The light reflects many times in the pentaprism's interior. The light then aligns with the viewfinder where you can see the scene the camera will record.
As you press the shutter to take the photo, the reflex mirror shifts to allow light to reach the film plane of a film camera or a light-sensitive imaging sensor on a digital camera. As the mirror moves out of the light path quickly, the scene in the viewfinder turns black briefly.
SLR Lens Mount
Each camera manufacturer designs a specific lens mount that connects the camera body with the lens. Even one manufacturer can develop different lines of camera bodies with a specific lens mount for a specific line of lenses. For example, one manufacturer created different lens mounts: the old screw-in mount in which the lens to attached by rotating into the camera; and the quick-release bayonet mount in which a button on the camera body was pressed to help detach the lens with a slight twist.
When you select a new lens, you need to make sure the lens matches the camera body's lens mount, as indicated in the user manual. SLR lenses are not interchangeable with different brands.
A third-party manufacturer of lenses can produce more economical lenses with different mounts specific to different camera companies. For example, if you plan to purchase a 28- to 70-mm zoom lens from a third-party manufacturer, you need to purchase the lens with the lens mount that matches the brand of the camera body.
Controls
These lenses show the distance scale and aperture scale.
Modern SLR lenses include an electronic connection that allows communication between the camera body and the attached lens. Adjusting the camera body's controls will adjust the lens settings. For example, an SLR with auto-exposure (AE) can set the lens's aperture and the camera's shutter speed to produce a correctly-exposed image. With the camera set to manual (M), you can manually adjust the lens aperture and shutter speed to suit the lighting conditions of your subject.
The lens barrel will indicate a distance scale with distances marked in feet (ft) and meters (m). The minimum focusing distance shows how close the subject and lens can be positioned and still achieve sharp focus. For example, if your lens indicated a minimum focusing distance such as 1.55 ft or 0.45 m, you can still achieve a sharp image with your subject standing two feet away from your lens.
The lens barrel will have a focus ring that rotates until your subject comes into focus. Modern SLR lenses include autofocus that allows the camera body to the focus the lens automatically. You can also opt to focus the lens manually by rotating the focus ring with your fingers to achieve focus.
Focal Length
According to Photokina, the growing market for SLR system cameras results in more development of lenses with a variety of focal lengths. For example, an ultra-wide zoom lens with a focal length ranging from 10 mm to 22 mm can capture landscape and cityscape shots to show a feeling of expansiveness. An SLR telephoto lens with a fixed 300-mm focal length can make distant wildlife subjects appear much closer in a compressed space. A 100 mm macro lens works well for close-up photography to magnify small objects such as flowers.
Tags: camera body, lens with, lens barrel, lens mount, reflex mirror
