Pol arisers

A cir­cu­lar po­lariser is with­out doubt the one fil­ter that every pho­tog­ra­pher shoot­ing land­scapes needs to own

Digital SLR Photography - - The Beginner ’s Guide -

iT can be ar­gued that, with ad­vance­ments in sen­sor tech­nol­ogy, dig­i­tal tech­niques, and edit­ing soft­ware, the ef­fects of some fil­ters such as nd grads and, to an ex­tent, nd fil­ters them­selves, can be re­placed dur­ing post- pro­cess­ing. brack­et­ing and ex­po­sure blend­ing can sim­u­late grad­u­ated nd fil­ters, whilst mul­ti­ple ex­po­sures over time can cre­ate an ef­fect re­mark­ably sim­i­lar to that of us­ing an nd fil­ter to achieve a long ex­po­sure. How­ever there’s one fil­ter that sim­ply can­not be repli­cated – the cir­cu­lar po­lariser ( CPL).

In order to fully un­der­stand how a po­lar­is­ing fil­ter works, we need to ex­plain a lit­tle bit about how light works, and the dif­fer­ent types of po­lar­is­ing fil­ters avail­able. Light con­sists of both elec­tric and mag­netic waves and, in un­po­larised light, these waves are trav­el­ling in chaos, os­cil­lat­ing on mul­ti­ple planes. Di­rect light waves that are re­flected off non­metal­lic sur­faces, such as glass, wa­ter or fo­liage, are par­tially po­larised and re­flected largely across one plane. a CPL fil­ter blocks these light waves from reach­ing your sen­sor at cer­tain an­gles, depend­ing on the fil­ter ori­en­ta­tion, ef­fec­tively sort­ing out the chaotic and per­pen­dic­u­lar waves, al­low­ing only light waves on a sin­gle plane to pass through. Why does all of this mat­ter? be­cause, in do­ing so, a po­lar­is­ing fil­ter can be used to block glare and reflections, to cut through haze and to sat­u­rate the colours in your im­ages. not to men­tion the two- stop light loss of­fers added cre­ative ben­e­fits.

There are two types of po­lar­is­ing fil­ter – a lin­ear po­lariser and a cir­cu­lar po­lariser. When it comes to dig­i­tal cam­eras, only cir­cu­lar po­laris­ers should be used; us­ing a lin­ear po­lariser can play havoc with me­ter­ing and aut­o­fo­cus sys­tems. a cir­cu­lar po­lariser com­prises two fil­ter rings that can be ro­tated in­de­pen­dently of one an­other – the front ring con­tains the po­lar­is­ing fil­ter, whilst the rear- most ring holds a quar­ter- wave plate. Ro­tat­ing the po­lar­is­ing fil­ter al­lows you to con­trol the di­rec­tion of po­larised light, ef­fec­tively like an on- off po­lar­i­sa­tion dial. The quar­ter- wave plate then con­verts this lin­ear light into cir­cu­lar po­larised light, al­low­ing your cam­era’s aut­o­fo­cus and me­ter­ing func­tions to op­er­ate prop­erly.

no Po­lariser

with Po­lariser

Above: A cir­cu­lar po­lariser is the per­fect tool for the dis­cern­ing out­door pho­tog­ra­pher, what­ever the weather.

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