When this occurs, the area of the sensor is incompletely exposed, causing a dark ring to appear around the borders of the image. Vignetting occurs when the lens format is smaller than the camera format. Doing this will have an effect, either vignetting or cropping, on the resulting image. In the ideal imaging system, a camera and lens would be designed for the same format, however, it is also possible to use camera/lens combinations with different formats. The diagram to the right illustrates the size difference between several standard camera formats. This format designation (e.g., 1/2', 2/3', 4/3') is a hold-over convention from when video was recorded using cathode-ray tubes and refers to the outer diameter of the video tube required for a given image size. Modern cameras that use CCD or CMOS sensors are specified for a camera sensor format, and similarly, lenses are designed to provide optimal imaging for a specific camera format. For details, see the text.Ĭombining Different Camera Sensor and Lens Formats Larger crop factors correspond to more overfilling of the camera sensor.Finally, a lens with a focal length longer than normal is known as a telephoto lens, which has a smaller field of view and a greater magnification of objects in the image.Ĭrop Factors for Different Sensor/Lens Combinations a A wide-angle lens has a focal length shorter than normal, which produces a wider field of view but has a tendency to exhibit barrel distortion effects towards the edge of the image. A lens with a focal length close to the diagonal length of the sensor format produces an image with a near-human field of view and is considered a 'normal' lens for that sensor format. There are three general classifications for lenses related to the image field of view. The table below lists the focal lengths needed to achieve the same field of view as the human eye for different sensor formats. As a general guideline, a 50 mm focal length lens and 35 mm format camera combination produces roughly the same field of view as the human eye (~53° diagonal). For a camera lens, the focal length determines the field of view of the camera system the longer the focal length, the smaller the field of view. The focal length (FL) is roughly defined as the distance from principal plane to the focal plane. Because the images were taken at constant exposure, for each f/# increase (by a factor of ~1.4) the amount of light collected by the lens is reduced by half.Īperture Size Effects (Click Photos to Enlarge) To illustrate the effect of different aperture sizes visually, the table below shows a sequence of images taken with the same lens (MVL12M43 on a DCU224C 1/2' format camera) for increasing f-numbers. While using larger apertures increases light collection, doing so reduces the axial in-focus region of the image, known as the depth of field. For example, a 50 mm focal length lens with a f/1.4 aperture has a bigger aperture and is therefore faster than a lens at the same focal length with a f/2.5 aperture. Where f/# is the f-number, f is the focal length and d is the entrance pupil diameter.Ĭamera lenses that can collect a lot of light (i.e., a low f-number) are known as fast lenses as they can be used with shorter exposure times and are ideal for low-light conditions. As the f-number increases, the aperture opening becomes smaller and less light is collected by the lens. Thorlabs provides the maximum aperture size in the tables below for each lens in terms of the f-number, which is expressed using the symbol f/# (e.g., f/1.4). Because of this, the aperture size affects the exposure time and therefore the speed of the camera. The aperture of the lens controls the amount of light that a lens can collect the more light a lens collects, the brighter the image.

Camera lens distortion of face