Human eye is better adapted to incandescent lamps; Expert makes argument for energy efficiency and ergonmics with modified lights.While much of the debate about the contentious white LED streetlights installed on Marine Drive has been confined to the realm of politics, a scientific study conducted by an associate professor at IIT Bombay has shown that the human eye prefers yellow luminescence. “The old incandescent lamps are close to the solar spectrum our eyes are evolved to be comfortable with,” said Dr Chetan Singh Solanki, of IIT’s Energy Science and Engineering department. “They also appear familiar because yellow lights have been used by society for hundreds of years. While the light they give naturally diffuses in all 360 degrees, the downside of it is that a lot of light is sent towards the sky and electricity wasted.”Solanki clarified that he is a votary of LED technology and that with “proper coating of phosphorous around the tube, an LED light can come very close to the yellow spectrum that old style incandescent lights have”. These fixtures, which use diodes to produce incandescence rather than filaments, can cause daily savings of “lakhs of volts of electricity,” he said.Dr Solanki was of the opinion that the debate should focus on distribution of light and mounting of LEDs. “The important thing is to design the distribution and angle of LED streetlights properly in order to give as much light even while spending a tenth of the electricity,” he said.The professor’s argument hinges on the Colour Resolution Index, an indicator that compares light spectrums and the solar spectrum to which the human eye has become accustomed. “Today, good quality LED lights in the market have a CRI that is higher than that of domestic appliances like tube lights,” he said, making an argument for both energy efficiency and ergonomics. “Perhaps an academic institution could study if the cause of residents’ ire [against white LED streetlights] is related to technical issues related to distribution and mounting of the lights. It would be a simple matter to check for any design inefficiencies.”Meanwhile, the political wrangling over the decision to switch from yellow lights to white LEDs has mostly involved the state being criticised for arbitrariness. “We are not against the concept of LED lights or new technology. However, this decision was taken without consulting residents or corporators. It is unfair to impose such decisions. You can't experiment with the city's most iconic road like this. We want the lights restored to yellow,” Shiv Sena’s south Mumbai MP Arvind Sawant told this paper recently. The leader of the youth wing of his party, Aditya Thackeray, joined the chorus with this tweet: “…Marine Drive is a pride and heritage road of Mumbai, the Queen's Necklace. It has to shine as yellow lights. We aren't against LEDs. Fully support energy saving and renewable energy, but options like Yellow LEDs cld have saved the charm from ruin. The light has made Marine Drive dull and dark, and we need to find a better alternative than the LEDs to save power.”Dr Solanki’s work is removed from such squabbles. He is known outside academia for designing the “glowing street” streetlight that runs on 6 watts of electricity and is being used in parts of Madhya Pradesh. According to him, complaints regarding dark spots and lack of safety at night on Marine Drive originate in inefficient design and distribution of bulbs. “The power LED tends to be more targeted, but with the use of diffusers and proper mounting, the emergence of dark spots can be prevented. In fact, targeted LED lights, if used efficiently, allow one to make particular unsafe spots brighter for certain hours of the night without inconveniencing residents living next door,” he said.