Apr 05, 2018 Written by SAMIUL ANSARI Lens
A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.
There is no major difference in principle between a lens used for a still camera, a video camera, a telescope, a microscope, or other apparatus, but the detailed design and construction are different. A lens might be permanently fixed to a camera, or it might be interchangeable with lenses of different focal lengths, apertures, and other properties.
Aperture and focal length:- The two fundamental parameters of an optical lens are the focal length and the maximum aperture. The lens' focal length determines the magnification of the image projected onto the image plane, and the aperture the light intensity of that image. For a given photographic system the focal length determines the angle of view, short focal lengths giving a wider field of view than longer focal length lenses. A wider aperture, identified by a smaller f-number, allows using a faster shutter speed for the same exposure
Number of elements:- the number of elements and their degree of asphericity — depends upon the angle of view, the maximum aperture, and intended price point, among other variables. An extreme wideangle lens of large aperture must be of very complex construction to correct for optical aberrations, which are worse at the edge of the field and when the edge of a large lens is used for image-forming. A long-focus lens of small aperture can be of very simple construction to attain comparable image quality: a doublet (two elements) will often suffice.
Lens mounts:- Lens mounts are designed for compatibility between cameras and lenses.There is no universal standard for lens mounts, and each major camera maker typically uses its own proprietary design, incompatible with other makers. The most common interchangeable lens mounts on the market today include the Canon EF, EF-S, EF-M, Nikon F manual and autofocus mounts, the Olympus/Kodak Four Thirds, Olympus/Panasonic Micro Four Thirds digital-only mounts and he Sony Alpha mount (derived from the Minolta mount) and the Sony E digital-only mount.
Types of lens,
Standard Lenses (~50mm):- A standard lens is the usual lens supplied with an SLR. They are good general purpose lenses having an angle of view close to the human eye. They are sharp, compact and lightweight.
Wideangle Lenses (<50mm):- The natural choice for landscapes, sweeping panoramas and other outdoor scenes, group shots and generally anything requiring strong perspective. In some situations a wideangle might be the only way to capture the entire scene without excluding an important element in the frame.
Medium Telephoto Lenses (85-135mm):- These lenses are perfect for portraits. Compared to a 50mm lens they isolate the subject from the background more and the increased focal length slightly flattens the image and gives more a natural and flattering perspective. Popular for candid photography.
Long Telephoto Lenses (>135mm) :- Used for sports, nature or other types of documentary style photography that requires you to be close to the action but cannot be close physically be it dangerous or timid. Like portrait lenses they are great for picking out the subject from the background.
Macro Lens:- Macro lenses can focus very close allowing real size, 1:1 image ratios, ie an object 10mm in size will appear 10mm on the 35mm frame. Excellent for nice close ups of insects or flowers.
Fisheye Lenses:- Distort the perspective to create a circular “fisheye” 180° image. A very specialised lens. Picking the correct subject is necessary but when you do can produce some memorable images. Focal lengths vary, 7~16mm.
Super Wideangle Lenses (<24mm):- Like wideangle but more so, but not as much as the fisheye. Great for exaggerated perspective or scenes from restricted vantage point. Favoured lens of the estate agent!
Super Telephoto Lenses (>300mm):- Longer telephotos and an eye-watering price tag to match. Can be heavy due to the amount of glass they contain. Often they have a tripod mount on the lens.