A camera lens


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A camera lens

  1. 1. A camera lens (also known as photographic lens, objective lens or photographic objective) isan optical lens or assembly of lenses used in conjunction with a camera body andmechanism to make images of objects either on photographic film or on other mediacapable of storing an image chemically or electronically.While in principle a simple convex lens will suffice, in practice a compound lens made up of anumber of optical lens elements is required to correct (as much as possible) the manyoptical aberrations that arise. Some aberrations will be present in any lens system. It is thejob of the lens designer to balance these out and produce a design that is suitable forphotographic use and possibly mass production.There is no major difference in principle between a lenses used for a still camera, a videocamera, a telescope, a microscope, or other apparatus, but the detailed design andconstruction are different.A lens may be permanently fixed to a camera, or it may be interchangeable with lenses ofdifferent focal lengths, apertures, and other properties.At first glance, digital photography would seem not to affect lenses, since it is a cameratechnology for the capture and storage, but not the creation, of images. However, electronicimage processing provides an opportunity to improve lens images far beyond a simplecontrast boosting Unsharp Mask.In 2004, the Kodak (Sigma) DSC Pro SLR/c (USA/Japan) digital SLR was loaded with opticalperformance profiles on 110 lenses so that the on-board computer could correct the lateralchromatic aberration of those lenses, on-the-fly as part of the capture process. Also in 2004,DO Labs DoX Optics Pro (France) computer software modules were introduced, loaded withinformation on specific cameras and lenses, that could correct distortion, vignetting, blurand lateral chromatic aberration of images in post-production.Lenses have already appeared whose image quality would have been marginal orunacceptable in the film era, but are acceptable in the digital era because the cameras forwhich they are intended automatically correct their defects. For example, onboardautomatic software image correction is a standard feature of 2008s Micro Four Thirds digitalformat. Images from the 2009 Panasonic 14-140mm f/4-5.8 G VARIO ASPH. MEGA O.I.S. andthe 2010 Olympus M. Zuiko Digital 14-150mm f/4-5.6 ED lenses (both Japan) have theirsevere barrel distortion at the wide angle settings automatically reduced by a PanasonicLUMIX DMC-GH1 and Olympus Pen E-P2, respectively. The Panasonic 14-140mm lens alsohas its chromatic aberration corrected. (Olympus has not yet implemented chromaticaberration correction.)In photography, a lens hood or lens shade is a device used on the end of a lens to block thesun or other light source in order to prevent glare and lens flare.The geometry of the lens hood can vary from a plain cylindrical or conical section (much likea lamp shade) to a more complex cut sometimes called a petal, tulip or flower hood (asshown in some of the pictures), which produce a reasonable good shade without blockingthe field of view of the lens and thus producing vignetting. Properly petal shaped lens hoods
  2. 2. produce more shade than normal lens hoods with the same end diameter. Square lenshoods may be even better.Lens hoods are more prominent in long focus lenses because the field of view has a smallerviewing angle than of wide-angle lenses. For wide angle lenses, the length of the hood (awayfrom the end of the lens) cannot be as long as those for telephoto lenses because of theviewing angle.Lens hoods are often designed to fit onto the matching lens facing either forward, fornormal use, or backwards, so that the hood may be stored with the lens without occupyingmuch additional space. Some lens hoods are flexible and collapse for storage.In addition, they offer some physical protection for the lens due to the hood extendingfarther than the lens itself.In photography and videography, a filter is a camera accessory consisting of an optical filterthat can be inserted in the optical path. The filter can be a square or oblong shape mountedin a holder accessory, or, more commonly, a glass or plastic disk with a metal or plastic ringframe, which can be screwed in front of or clipped onto the lens.Filters modify the images recorded. Sometimes they are used to make only subtle changesto images; other times the image would simply not be possible without them. Inmonochrome photography coloured filters affect the relative brightness of different colours;red lipstick may be rendered as anything from almost white to almost black with differentfilters. Others change the colour balance of images, so that photographs under incandescentlighting show colours as they are perceived, rather than with a reddish tinge. There arefilters that distort the image in a desired way, diffusing an otherwise sharp image, adding astarry effect, etc. Supplementary close-up lenses may be classified as filters. Linear andcircular polarizing filters reduce oblique reflections from non-metallic surfaces.Many filters absorb part of the light available, necessitating longer exposure. As the filter isin the optical path, any imperfections—non-flat or non-parallel surfaces, reflections(minimized by optical coating), scratches, dirt—affect the image.There is no universal standard naming system for filters. The Written numbers adopted inthe early twentieth century by Kodak, then a dominant force in film photography, are usedby several manufacturers. Colour correction filters are often identified by a code of the formCC50Y—CC for colour correction, 50 for the strength of the filter, Y for yellow.Optical filters are used in various areas of science, including in particular astronomy; theyare essentially the same as photographic filters, but in practice often need far moreaccurately-controlled optical properties and precisely-defined transmission curves thanfilters exclusively for photographic use. Photographic filters sell in larger quantities atcorrespondingly lower prices than many laboratory filters. The article on optical filters hasmaterial relevant to photographic filters.
  3. 3. There are a wide variety of digital SLR camera cases for you to choose from.Camera cases come in all shapes and sizes, from the simple form-fitted case to a backpackwith pouches galore.So how do you select the right one?It comes down to one important question: how much gear do you need to take the photosyou love?The Case for a CaseIf youve just spent 500+ dollars (or any significant amount of currency) on a digital SLR itmakes sense to protect it.Heres the thing: digital SLR cameras are accident-prone.Most compact cameras can take a beating. The lens is enclosed in the camera body whennot used, and the camera doesnt have a lot of joints where water and sand can sneak in.Digital SLR cameras have lots of openings: one for the lens, one for the battery, and one forthe memory card...the list goes on.Each one of these opening presents an opportunity (although slight) for your cameraselectronics to get affected by wind and weather.It doesnt help that SLR lenses extend from the camera body at all times, and are easy tobang and scrape on rocks and other sharp objects.Digital SLR camera cases are designed to prevent these kinds of mishaps.Types of Cases:There are 3 basic types of digital SLR camera cases for the average photographer:Form-fitting casesSmall bags and camera packsBackpacks and sling packsForm-fitting digital SLR camera cases are designed for specific cameras.Since they are designed to fit snugly around the camera body, you cant use them withcameras that have different shapes. They arent one-size-fits-all solutions.Small bags and fanny packs are best suited for one camera with several lenses. Theyreversatile: these digital SLR camera cases can carry a variety of camera models.They are great for hiking trips and other times where you dont need to pack a lot of gear,but want your camera along for the ride.
  4. 4. Backpacks and sling packs are for photographers who want to carry lots of gear all the time.Theyre designed for longer trips (not day hikes) when youre not sure exactly what type ofphoto opportunity might present itself.Which One to Get?Now Ill get back to that question about digital SLR camera cases.How much gear do you really want?One Camera and LensA form-fitting digital SLR camera case is a good option if you dont think youll ever use morethan the camera and lens that you purchased.If the camera and lens takes the photos you love, then get a case that fits it well. This willkeep it covered and protected when not in use.The only trick is finding the right case for your camera: heres a list of digital SLR cameracases fitted for specific camera models.One Camera plus ExtrasIf you think that you might branch out in the future and get an extra lens or a flash for yourcamera, the form-fitting case wont work.Instead, opt for a small bag that has enough room for your camera plus a few accessories.A camera case like this gives you some room to grow so that you can explore more styles ofphotography in the future.Skys the LimitFor all of you with impulse-control issues (like me) a backpack or sling pack is probably agood idea.I started out with one camera and one lens.Today I have 2 camera bodies, 4 lenses, three external flashes, a tripod, filters...you get thepicture.The nice part about having a digital SLR camera case large enough to store all of this gear isthat its all in one place.If I have to run out the door quickly to take some photos I can do it without worrying aboutwhere Ive put all of my camera gear.Recommendation:The only digital SLR camera case that I can personally recommend is one that I have usedextensively: the Adorama Slinger Bag.
  5. 5. This bag is definitely for anyone with a lot of gear (or who expects to have a lot).Here are some of the reasons why I chose it:Main compartment closes off with a clip instead of a zipper, allowing quick access to theinsideIncludes both shoulder strap and waist strap and is quite comfortable when carrying 10pounds of gearPlenty of pockets allow me to carry extra memory cards, batteries and other smallaccessoriesAll my stuff fits into one bag - great for travel, when I want to keep everything with meFor the style conscious, it comes in Black, Green, Gray, Maroon, Navy and Camouflage