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    Decoding the lens jargon

    The almost sentence-long collection of letters and numbers on the side of a lens barrelcan tell you all sorts of things about a lens. But the details which you should probably paythe most attention to are those which detail the focal length, maximum aperture, lensmount and format type.

    Focal length

    Focal length is expressed in mm and a higher number means a bigger zoom, while alower number mean the lens can be used for wider shots. As a rough reference, thehuman eye is said to see about the equi alent of !"-#" mm on a full frame camera $moreon that later%. A number lower than !"-#" mm will ta&e in a bigger iew than younaturally see, while higher numbers mean focus will be on a smaller aspect of your iew.

    http://www.gizmag.com/camera-lens-buying-guide/29141/pictures#20
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    'f the lens has a focal length range with two numbers $say ()-*" mm% this means it+s azoom lens and is capable of zooming and being used at any point across that range.

    owe er, if there is a single focal length number $#" mm for instance% it+s a prime lens,so ta&ing in more or less of the iew will require you to get closer or further away fromyour sub ect. Traditionally, primes ha e been considered to be optically superior tozooms, because trade-offs ha e to be made when producing zoom lenses. But that+s not tosay that some zooms are not better than some prime lenses.

    To ma&e understanding focal length more difficult, the same focal length lens gi esdifferent iews on cameras with arious sensor sizes, because of the crop factor $thesensor only ta&es up part of the pro ected image%. As a result, many manufactures gi e a!# mm-format equi alent on lenses designed for cameras with smaller sensors and in thisarticle descriptions are based on on !# mm-format. Therefore, if your camera has asmaller sensor, and there+s a good chance it does, you+ll need to consider this whendeciding which lens you need.

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    'f you+re using a full frame camera there+s no calculation needed, a lens will gi e you thefield of iew you+d expect from its number. 'f your camera has an A /-0 sensor $1i&on23 2/45s, /ony 1637% it has a crop factor of 8.# - meaning you multiply the lensfocal length by 8.# to get its equi alent !# mm-format focal length. For 0anon A /-0cameras that number is 8.9, for :icro Four Thirds cameras it+s (." and for the 1i&on 8

    series it+s (.;.

    That means a !# mm lens would gi e a field of iew equi alent to #9 mm on an A /-0camera li&e a 0anon ;"2 and equi alent to ;" mm on a :icro Four Thirds camera li&ethe

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    /ome zoom lenses ha e a ariable maximum aperture meaning that it changes dependingon focal length. /o, while a 8*-("" mm F!.#-#.9 lens would ha e a maximum aperture ofF!.# at 8* mm, it would be be F#.9 by the time you zoomed to ("" mm.

    Lens Mount

    't goes without saying that you want to buy a lens that will attach on your camera, andthis is &nown as the lens mount. 0amera manufacturers generally ma&e lenses with

    proprietry mounts which will only fit their de ices, sometimes ha ing multiple lensmounts for different camera lines. The ma or exception to this is :icro Four Thirdslenses which can be used on respecti e

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    these are things li&e the 0anon 6F-:, Fu ifilm 3F, 1i&on 8, /ony 6, /amsung 13 andentax . As mentioned earlier,

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    What they are: ltra Cide angle lenses ha e a focal length of around less than () mm$in !# mm-format%, this means they can ta&e in a wider scene than is typical, thoughthey+re not only about getting all of a sub ect into a shot. 5ectilinear ultra wides help &eepstraight lines, ust that, while fisheyes will reproduce buildings with cur ed walls.

    Image characteristics: Because of the wide field of iew, shots with ultra wide anglelenses typically feature a large depth of field. 'mages tend to pull in sub ects that are

    close, and push away more distant ones ma&ing them appear further apart. erspecti edistortion of ultra wides can gi e falling-building-syndrome $where ertical linescon erge% but this can be corrected in post-processing, or minimized with goodtechnique.

    What they are used for: Chile often seen as a specialist lens, ultra wide angles can beused in a number of ways. Typical uses include landscape, architecture and interior

    photography. 6 en the distortion can be used creati ely, especially when using fisheyelenses.

    Wide Angle

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    What they are: Typically co ering a focal length between () mm and !# mm, CideAngle lenses are a ailable as primes or zooms and come with either ariable or fixedmaximum aperture.

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    What they are: Telephoto lenses are those with a focal length in excess of ;" mm,though many people would argue that EtrueE telephoto lenses are ones which exceed 8!#mm. They focus on a much narrower field of iew than other lenses, which means theyare good for focusing in on specific details or distant sub ects. They are generally largerand hea ier than equally specified wider lenses.

    Image characteristics: Because they ha e a narrower angle of iew, telephoto lenses bring far away sub ects closer. They can also ha e the effect of compressing the sense ofdistance in a scene and ma&ing ob ects appear closer together. A narrow depth of fieldmeans that a sub ect can be in focus with a blurred bac&ground and foreground.

    What they are used for: 'n addition to being used to photograph sub ects you can+t $ordon+t want to% get close to - li&e sports or wildlife - telephoto lenses can be used forshooting portraits and e en landscapes where their normalization of relati e size can beused to gi e a sense of scale.

    Super#oom

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    What they are ? /uperzooms are do-it-all lenses which co er focal lengths from wide totelephoto. They can be good for uses in situations where you can+t or don+t want to bechanging lenses and they normally change in length as you zoom.

    Image characteristics: Because compromises ha e had to be made producing a do-it-all

    lens, superzooms do not ha e the same image quality of more dedicated lenses and oftenha e slower and ariable maximum apertures.

    What they are used for:

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    What they are ?

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    Cith changes in focal length and maximum aperture come another set of lens changes,namely size, weight and price. 'deally we+d all be wielding a 89-9"" mm F8.* lens.

    nfortunately, not only does physics dictate that such a lens would need to be huge andery hea y, it would also cost a fortune to produce, if it was e en possible.

    As such, any lens is going to ma&e compromises to fit into a pac&age of a size and weightwhich suits its users. 6xtreme focal lengths and larger apertures mean bigger and hea ierlenses, which along with the bigger price-tags is why they are typically used by

    professionals who can ustify purchasing them.

    Image sta(ili#ation% (uild )uality and *ideo

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    There are a number of other features which you may want thin& about, regarding yournext lens. 'mage stabilization allows for use of slower shutter speeds without sufferingcamera sha&e $though some brands incorporate this into camera bodies rather than thelens%. /tabilization is also ery handy if you+re shooting lots of ideo, in which case youmight also want to thin& about lenses with power zooms which can zoom at ad ustablespeeds.

    Ceather-sealing means you can use your lens $assuming your camera is equally weather-sealed% in extreme weather conditions and normally also means a higher le el of buildquality.

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    Below are a number of typical situations that &it-lens-toting photographers often findthemsel es in. For each example, we+ e highlighted some of the factors that should beconsidered when trying to find the right lens for the ob. Chile these are factors whichare rele ant whate er camera and lens system you+re using, in each case we+ e alsohighlighted a couple of lenses that would be a good choice for specific set-ups without

    blowing the budget.

    I &ant an all,day tra*el lens

    Chen you+re on holiday or tra eling, you probably don+t want to be lugging se eral lensesand cameras around with you G unless you+re the most dedicated of photographers, that is.'t+s often the same if you+re trying to en oy a day with the family and don+t want to spendall day changing lenses and moaning about your bac&.

    As such, a good all-day or tra el lens would be one that was easy enough to carry around, but still offered you the freedom to capture shots from landscapes to portraits, and zoomin on distant ob ects. For :icro Four Thirds shooters, that could be something li&e the

    anasonic 4umix H Iario 8)-8)" mm f>!.#-#.9, or the AF-/ 23 1'@@!.#-#.9H 62 I5 '' if a 23 1i&on is your 2/45 or choice.

    I &ant to do street photography

    http://www.gizmag.com/camera-lens-buying-guide/29141/pictures#27
  • 8/14/2019 DSLR lens.doc