Want to elim­i­nate that grainy look in your pho­tos? Hans We­ich­sel­baum runs you through the causes of noise in your images and how to make it go away

No, by ‘noise’ I don’t mean the an­noy­ing click your DSLR makes when you shoot in a quiet con­cert hall. I am talk­ing about ‘image noise’, the grainy-look­ing arte­facts that be­come vis­i­ble, es­pe­cially in the shadow ar­eas, when you push the ISO set­ting hard enough. Noise is al­ways some­thing un­wanted, whether it comes through your ears or through the eyes. Noise in pho­tog­ra­phy is de­scribed as a phe­nom­e­non which wasn’t part of the orig­i­nal scene when you took the shot. Image noise has al­ways played a role in pho­tog­ra­phy — just re­mem­ber the days when we pushed our colour film to ISO 800. It boasted a 1.3-megapixel sen­sor, weighed in at 1.6kg and stood over 18cm tall — all for a cool US$17,950. Image 1 shows you this cam­era in ac­tion at ISO 1600. In those early days, Ko­dak re­ferred to these sen­si­tiv­ity/ noise lev­els as ‘very ag­gres­sive’; oth­ers la­belled them as ‘bo­gus’.

This was barely a gen­er­a­tion ago, and we have come a long way when you think of the pic­tures you get out of your mo­bile phone. On the other hand, not much has hap­pened in the pro­fes­sional full-frame (35mm) mar­ket over the last five years. Cam­eras sport­ing 30-plus megapix­els are be­com­ing more com­mon, with Canon’s 5DS mod­els lead­ing the flock with 50-plus megapix­els. How­ever, note that the na­tive ISO range has dropped back to 6400, com­pared with 25,600 for the 5D Mark III, which has half the pixel count and is more than four years old. Cam­era

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