Change the Bulbs, Save your eyes!

 Courtesy: Md. Jikrul Sayeed Hossain, Lecturer, Department of EEE, Green University of Bangladesh

Hello everyone. Hope that it's a good day for you. We live in our room, most of the time. It could be your home, office, factory, class or others. What is the crucial need at the time of living? It's the light that you need to see perfectly. Human eyes could see almost everything in lower light. So, most of us don't care about the appropriate lights inside the room. Have you ever faced problems in your eyes? Yes, most of us are facing issues in our eyes at any stage of life. I am also wearing glasses. Is that only for your ages or other factors? No, there is an important factor that you have to visualize something in an appropriate lighting condition. Otherwise, you or your children will face problems soon. Let's start with the general idea or calculation for your room. Remember that we are calculating for everyone so that it will ignore some factors as engineers' calculation at the time of designing is complex to understand.

Photo Courtesy: Colin Behrens at pixabay

Think one minute, how do you buy the lights from the shop?  You and I go to the shop & the shopkeeper suggested a bulb of like 10/12/16/18 Watt; we accept that and fit it to our room. Is the shopkeeper know how and where you are going to use the light? Sometimes they ask for the size of space; what do we say? Medium/big or small room. They even suggest 5-9W light for a room also. Why do we buy that? To save money, we don't want to think about the eyes, which is the most important part of our lives. This same thing I have done a lot of times. After facing difficulties at the time of reading, I have changed my mind, and now I use a simple rule to at least calculate an approximate requirement. 

So, the main factor behind the scene is Lumen (the SI unit of luminous flux, equal to the amount of light emitted per second in a unit solid angle of one steradian from a constant source of one candela). Forget the definition; remember, "Lumen" is just an SI unit to measure the light. So before considering any light, you have to calculate how much lumen light is required in your room. We assume that your room's height is on average 8 to 10 feet, and the light is surface or wall-mounted (before I said, ignore some engineering factors like angle position to make it simple).

Photo Courtesy: LED Supermarket at pexels

Let consider your bedroom is 13x12 feet (length and width); thus, the area is 156 square feet. Forget about the US/UK standard; generally, you need 10-20 lumen per square foot. So, you will need (156x10 – 156x20) 1560-3120 lumen. Most of the technical people suggest going for the average of your lighting requirements. So, in my selection, it will be 15x156 = 2340 lumen. If I select a light from Super Star Electronics Ltd, I will need a (2340/95=24.6W) 24W+ light, and in the market, a 26W lamp is available.

[ Lighting experts recommend the following light levels for different rooms in a home. These recommendations apply to typical room illumination, such as that provided by ordinary ceiling lights or several lamps. Additional, concentrated light (task lighting) would most likely be included in places meant for work or reading to brighten specific regions where light is critical, such as kitchen worktops. ]

Now in table-1, you will get an idea about the general requirements for different rooms.

Room type

Lumens per square foot

Living room

10-20

Dining room

30-40

Bedroom

10-20

Bathroom

70-80

Hallways

5-10

Kitchen (general lighting)

30-40

Kitchen (task areas)

70-80

Laundry room

70-80

Table-1: General Requirements of light levels. [courtesy: Illuminating Engineering Society]

Have you ever checked the box of your light? Just find it in the figure-1. Every standard package will provide the watt lumen ratio or Lumen per Watt in its specification. See the figure-1, and you will get the spec from the box by which you can easily calculate which is the perfect light for your bedroom. 

Figure-1: Typical light specification (Courtesy: left spec. - 5W LED light, Transcom Electronics & Transtec Lighting Ltd; right spec. - 18W LED light, Super Star Electronics Limited)

Figure-2: Typical Lumen values concerning wattage ratings and types of bulbs. [Courtesy: Alcon Lighting Inc.]

In conclusion, you can follow as,

  1. First, you have to calculate the area of your room in square feet. (it's one minute task)

  2. Then find the lumen requirement from a suitable reference like in table-1 (better to go with the average value)

  3. Then go to the shop, you know how many lumens you need, so buy some higher value like you need 2350 lumen then purchase 2400+ Lumen, as we all know that the light performance reduces after some days. Most of the time, we typical Bengali people never change the light until it burns out. But you can observe that most of the LED lights won't burn out so fast but reduce it's efficiency after a certain time.

  4. To save the eyes, please do not look towards the price or wattage rating. If you use a 25W bulb and per unit bill is 6 taka, then lighting up the 25W bulb for 40 hours will cost you only 6 taka. Is that so much costly for you? 

  5. Use any android app to measure the lumen ratings (good quality phones gives almost perfect value or use more than one phone to measure the lumen rating) so that you can change the light when it is time. Please do it for the child and older people in your home. Care for them if you don't care for yourself.

So, it's up to you. I have been suffering from many problems in both my eyes for a long time. Almost every test result is ok, most of the time, but the main problem is my lighting issues and the time I am using the screens (both phone and laptop) with high gamma rays. I am a sufferer, so every time I visit anyone's house, I try to convince them to follow the exact or approximate standard to maintain the light requirements in every room. Thank you a lot, for reading this long story. Hope that you will realize the importance of lights before it's too late. Have a good time. Goodbye for now.

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