http___m.metro-portal.hr_ipad-izaziva-nesanicu-kindle-puno-blazi-za-oci_38950_1.xml
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The bright light emitted by an iPad could give some people reading before bedtime a bout of insomnia, researchers suggest. This is because the iPad uses a back-lit display rather than the "e-paper" found in other popular e-readers such as the Kindle that mimic the printed, duller page by reflecting light from elsewhere. "If you're using a Kindle – which doesn’t use a significant light source – that may potentially have less of an impact compared to a device like a laptop or an iPad with more significant light exposure," said Alon Avidan, a neurologist and associate director of the Sleep Disorders Center at the University of California, Los Angeles (UCLA). Sleep researchers have long known that light inhibits the release of melatonin, a hormone that settles the body into sleep mode toward evening time. "Melatonin is pro-sleep," said Frisca Yan-Go, director of the UCLA Sleep Disorders Center. Any artificial light source at night, whether it be from a television or a bedside lamp, can mess with the body's melatonin production, Yan-Go said, which rises when darkness falls, then tapers off toward morning as part of a natural cycle called the Circadian rhythm. According to Yan-Go and other sleep researchers, the reason for concern with the iPad over other forms of late-night light is that readers hold the device relatively close to their face. In theory, this could mean that the iPad affects the body's melatonin cycle more than watching late-night reruns on a television that is clear across the room, Yan-Go said. The fact that the iPad has a full-color screen – blue light in particular sparks alertness – and offers Web browsing and other engaging computer activity, unlike other dedicated e-readers, could also keep people from getting a good night's rest, scientists say. Yan-go said that she has not yet had patients complain about iPad-induced insomnia – perhaps because the device is so new – but she nevertheless recommends against using it as an e-reader given past cases of patient restlessness related to laptops and television. "You really want the [sleep] environment to be quiet and dark," Yan-go said. E-reading before bed The centuries-old tradition of reading a paperbound book before retiring has been going digital recently. Sales of e-readers continue to boom and are expected to nearly triple from about four million sold last year to over 11 million in 2010, according to a new report by Digitimes Research. Massachusetts-based E Ink Corp, which makes the e-paper used by major e-readers including Amazon's Kindle and Barnes & Noble's Nook, aims to provide a "true book-like experience" for its customers, according to the company's Web site. E-paper technology simulates the look of ink on paper on a screen by electrically arranging little charged capsules filled with black- or white-pigmented particles. Rather than emitting light of its own, like traditional computer screens and the iPad, an e-paper screen reflects ambient light in a room or outdoors, just as a real book would. This makes e-paper devices easy to view even in direct sunlight, a big plus for consumers with the summertime reading season right around the corner. The iPad, meanwhile, uses a 262,000-color, liquid crystal display (LCD) that must be back-lit because these liquid crystals do not shine on their own. Using an iPad to read at night does avoid the complication of waking a partner by turning on the bedside lamp or having to use a flashlight under the covers. Yet because the iPad beams light directly into a user's eyes, reading on it is similar to working on a computer late at night – another practice that sleep experts advise against when it comes to preparing for imminent slumber. Seeing blues while racking up Web views Beyond light emission, the iPad's colorful display could also contribute to insomnia when compared to the black-and-white screen of a Kindle, said Avidan. Cells in our eyes are more sensitive to blue light than other colors, a characteristic that has evolved in humans to triggers wakefulness upon the sight of an azure sky in the morning. "When you look at an LCD screen that has more rich colors in the blue range, that could conceivably have an additive effect" on insomnia, Avidan said. The temptation to do work on an iPad could also keep people from snoozing. "The problem with someone surfing the Web with an iPad is that it's engaging," Avidan said, whereas "the Kindle is more for someone who is just reading." Lights out Overall, Avidan thinks that the risk to most people losing sleep from e-readers is minimal. "For a typical person who doesn’t have problems falling asleep, if they're using a Kindle or an iPad or whatever, they probably don’t need to worry," Avidan told TechNewsDaily. "But if they suffer from insomnia and have difficulty falling asleep . then using artificial light from, say an iPad or a laptop, that certainly can have a detrimental effect." Other researchers are skeptical, however, that the iPad and other electronic devices pose all that much of a hindrance to getting some shut-eye. "The amount of light coming off a computer or an iPad is not anywhere near bright enough to set Circadian cycles," said Michael Marmor, a professor of ophthalmology at Stanford University. "Outdoor light is many thousand-fold brighter than any indoor computer or ordinary room light," he said, which is why jet-lagged travelers are told to get outside to help reset and gauge their internal clocks to the local day-night norms. "I think people should not worry about lighting effects from either the Kindle or the iPad," said Marmor. "What will keep you awake is the news of the day . or a really good book." • Nook Outnumbers Kindle, Analyst Says • eBook-Reader Reviews • The E-book Battle: You Win
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iPad izaziva nesanicu, Kindle puno blaži za oči Danas je stoljetna tradicija čitanja papirnatih knjiga i novina poprimila digitalnu dimenziju - a to ima svoje posljedice Jarko svjetlo koje emitira iPad kod nekih ljudi može izazvati nesanicu, naročito ako u njega gledaju prije spavanja. Razlog tome je sasvim jednostavan - iPad ima drugačiju pozadinu na zaslonu od ostalih e-čitača kao što je Kindle koji pak imitira papir i čije je osvjetljenje malo blaže. Laptopi i iPad imaju jače osvjetljenje ekrana, objašnjava Alon Avidan, neurolog i jedan od direktora Centra za poremećaje u spavanju Sveučilišta Kalifornija. Istraživači već neko vrijeme znaju da svjetlost često ometa lučenje melatonina, hormona koji priprema tijelo za san. To potvrđuje i Frisca Yan-Go iz istog Centra. Yan-Go kaže da je problem s iPadom u tome što ga čitatelji drže relativno blizu lica i očiju. U teoriji, svjetlost iPada zato prekida normalne procese vezane uz melatonin čak više nego što je to slučaj s kasnim gledanjem televizije. Obzirom da iPad ima ekran sa svim bojama - plava boja potiče budnost - i nudi mogućnost surfanja internetom i ostale računalne zanimacije - Yan-Go iznosi argumente protiv korištenja iPada za čitanje prije spavanja; već se zna kako djeluju televizija i računala. „Želite da vam okolina u kojoj spavate bude tiha i tamna", kaže ona. Danas je stoljetna tradicija čitanja papirnatih knjiga i novina poprimila digitalnu dimenziju. Prodaja iPada i ostalih e-čitača raste velikom brzinom; prema izvješću Digitimes Researcha, prodaja će se ove godine utrostručiti i dosegnuti čak 11 milijuna primjeraka. Zbog spomenutih problema s jakom svjetlošću zaslona, Kindle i Nook bi mogli profitirati nauštrb iPada jer oni koriste tehnologiju takozvanog e-papira kojemu je cilj stvoriti dojam da na čitačima čitate tiskani tekst. Tehnologija e-papira simulira tintu na papiru preko specijalno određene raspodjele nabijenih kapsula s česticama bijelog ili crnog pigmenta. Umjesto da emitira vlastitu svjetlost kao iPad, laptopi i monitori računala, e-papir reflektira ambijentalnu svjetlost, bilo u zatvorenoj sobi ili u parku na klupi, baš kao što je slučaj s čitanjem prave knjige.Zbog toga ga je lako čitati i na izravnoj Sunčevoj svjetlosti, a to je velika prednost, naročito kad se uzme u obzir da je broj ljetnih čitatelja na plaži sve veći. iPad s druge strane ima LCD ekran s 262,000 boja koji mora imati pozadinsko svjetlo jer kristali ne svijetle sami od sebe. Njegova jedina prednost je u tome što navečer ne morate paliti lampu kako biste čitali i tako ometali partnera dok spava. Ali svjetlost iPada udara izravno u oči čitatelja kao što je slučaj s računalima, a stručnjaci savjetuju da se to što više izbjegava kako ne bismo imali problema sa spavanjem. I to plavo svijetlo koje dominira, kaže Avidan, jače djeluje nego crno-bijeli izgled Kindlea. Stanice u našim očima puno su osjetljivije na plavu svjetlost nego na druge boje; evolucijski rečeno, to je zato kako bismo se lakše razbudili ujutro kad vidimo plavu zoru i kako bi naše tijelo znalo da je vrijeme spavanja gotovo. LCD ekran iPada s raznim nijansama plave i ostalih boja samo može pogoršati stvar i držati vas budnima kad ne treba. Ipak, Michael Marmor, profesor oftalmologije sa Sveučilišta Stanford, poprilično je skeptičan. Po njegovim riječima svjetlost iPada i ostalih sličnih uređaja nije dovoljno jaka da poremeti cirkadijski ritam. Osim toga, svjetlost dana je nekoliko tisuća puta jača od računala; upravo se zbog toga zrakoplovnim putnicima savjetuje da uzađu na otvoreno i prilagode se vremenskoj zoni. „Mislim da se korisnici Kindlea ili iPadane bi tgrebali brinuti oko učinaka njihova osvjetljenja. Ono što će vas držati budnim je vijest dana... ili jako dobra knjiga", zaključuje Marmor.