HUMITSU CORPORATION – JAPAN

How to choose appropriate desklamp

The guidelines help you choose the best reading light for your eyes

At some point in our childhoods, we were all warned that reading in poor light would ruin our eyes.

Later on when many of us got glasses, we even felt guilty about the time we spent under the covers reading bedtime stories by flashlight. But was poor reading light really the cause of our vision loss?

Contrary to popular belief, the answer is no. Reading in low light does not ruin eyesight. Most eyes worsen simply as an effect of aging.

However, while doctors agree that there is no evidence of poor reading light being detrimental to vision, good reading light can reduce uncomfortable short-term effects such as headaches or eye strain as well as make reading more enjoyable.

The guidelines help you choose the best reading light for your eyes
The guidelines help you choose the best reading light for your eyes

The guidelines below will help you choose the best reading light for your eyes.

Perhaps the most important choice to make when choosing a reading light is the kind of fixture you should use. Is overhead lighting, or reading next to a window, enough? Or would a more concentrated light be preferable?

Here’s what we recommend.

While reading in dim light will have no long-term effects on your vision, it does place an uncomfortable strain on your eye muscles.

Your visual muscles will want to relax to collect the most light, but at the same time they will try to contract to keep the words on the page focused on the retina.

Therefore, to reduce the conflict in your eye muscles when you’re completing a high-concentration task such as reading, it’s important to focus bright light directly where it is needed.

We recommend using a desk lamp. Desk lamps are small lamps that can swivel and be raised or lowered to help direct the light.

But while desk lamps are best due to their multi-directional capabilities, a table lamp with a lampshade that directs light downward (rather than out into the room) would also be a suitable option.

Is the LED desk lamp safe?

At present, LED lighting technology is mature enough to take over the market previously dominated by the conventional incandescent and fluorescent lighting.

Task lighting fixtures are increasingly using LEDs as the light sources for visually demanding tasks. Theoretically LED lighting is safe if this technology is implemented in a correct way.

However, the lighting industry is in a rush toward the cutdown of manufacturing cost for maximum market penetration. Lighting manufacturers aggressively ‘optimize’ their BOM sheets by every possible means.

As a result, the economics of LED lighting in terms of operating cost and initial purchase cost is so attractive that nearly every lighting application is shifting to this technology regardless of its potential negative impact on human health.

Which light is good for the eyes?

Just as it’s important to have a desk or table lamp concentrating light onto your book, it’s also important to couple this with comfortable, evenly distributed lighting throughout your room.

A common mistake people make when choosing light for reading is turning on a bright lamp in a dark room. Your pupils dilate from the dark when they wander off the page, which can make your eyes become easily fatigued – a reason many of us quickly become tired when reading in bed at night.

It’s also helpful to avoid reading by light that reflects a lot of bright glare, such as from a computer screen.

The constant shifting of pixels from reading off a computer or any screen with glare can put a lot of strain on your eyes. Doctors term this Computer Vision Syndrome.

Avoid reading from a computer whenever possible during your leisure time, or at least dim down your screen to lessen the glare.

Reversing the color scheme, such as white text on a black background, also mitigates eye strain.

Desk lamps are equipped for high intensity illumination in short distances and small areas.

The close, consistent engagement between the light source and human eyes attach great importance to color quality.

Unfortunately, color quality has been one of the major challenges facing LEDs as an artificial light source.

The American Medical Association (AMA) last year issued a report regarding the human and environmental effects of LED lighting.

While we think the report exaggerated the health risks associated with LED lighting, we have sufficient reasons to magnify the attention to the health concerns raised from using LEDs as the light sources for visually demanding tasks.

We’ll try to describe our concerns from an industry insider’s perspective.

a. Blue Light

The hazard of blue light is widely acknowledged. The blue light at a peak wavelength value between 460 to 480 nm may suppress melatonin, an anti-oxidant and suppressant of tumor development.

Reduced melatonin levels may increase likelihood of developing cancers and circadian rhythm disorders.

Repeated exposures to blue light will cause a photochemically induced retinal injury, permanent blue blindness, or irreparable degenerative tissues.

The color emitted by an LED is basically defined by the materials from which it is formed. White light is produced by using the principle of color mixing in which a phosphor coating serves as a wavelength converting element to mix with the blue light emitted from the light emitting diode to generate white light.

The phosphor based white LEDs are currently the dominant light sources for general purpose lighting because they’re relative easy to manufacture.

However, phosphor based white LEDs require carefully designed encapsulation to avoid premature degradation of the phosphor layer so that color-mixing equation is maintained and the excessive blue light will not leak through the entire LED package.

In general, phosphor based white LEDs are very safe and have tremendous successful applications in every sectors.

So it’s rare that LEDs will pose direct exposure of excessive blue light if they’re manufactured by reliable companies.

The problem lies in the side of some luminaire manufacturers. For manufacturers who’re constantly seeking cost optimization in whatever means possible, fake brand LEDs are a realistic concern.

These cheap LEDs are generally fabricated for initial functional similarities with other brand name LEDs and may seldom take the product stability factor into their design, formulation and manufacturing process.

Another concern is that LEDs generate heat during the electrical-opto conversion.

Poorly designed or low cost thermal management systems may lead to the premature deterioration of key LED packaging components.

Either the congenital instability of cheap/fake LEDs or the premature deterioration caused by poor system design might produce an excessive amount of blue light leakage.

b. Extremely High CCT

Correlated color temperature (CCT) is intended to characterize the human perception of a white light source by comparing its hue with a black-body radiator.

For a general consumer, CCT is just a feeling of warmness versus whiteness of the light source. Hence we see the classifications such as “Warm White” (2700-3500K), “Neutral White” (3500-5000K), and “Cool White” (5000-6500 K).

The phosphor composition incorporated in the LED defines the CCT of a white LED. While it’s true that high CCT LEDs emit proportionally more blue light than low CCT LEDs, the amount of blue emission in LEDs with CCT below 6500 K does not reach hazardous levels.

c. One thing is for sure – LED light sources with low CCT (warm white) are safe to use.

Unfortunately there’s an ignorant preference for high CCT lamps among the general consumers who think the whiteness of light sources is positively proportional to the level of visibility in a space illuminated by the light sources.

This preference will most likely influence their decisions in buying LED desk lamps.

On the other side, many lighting manufacturers are terribly irresponsible on this issue. In fact they are literally no more knowledgeable than the general public.

d. Glare

Glare is the single biggest issue for LEDs to be used as the light sources for LED desk lamps and other demanding applications.

LEDs, unlike fluorescent lights which emit light that spreads out very much over a wide area, are point light sources by nature. The concentrated light-emitting spots may cause discomfort glare or disability glare.

This is why most LED luminaires use secondary optic systems to achieve optimal luminance levels and light distribution uniformity.

LED desk lamps are probably one of the most challenging lighting systems for industrial designers of LED secondary optics.

A good optical design for LED task lights starts from effectively mitigating the harsh, concentrated beam to obtain a soft and pleasant light distribution.

Glare control usually involves a huge investment in sophisticated industrial design and proprietary optic systems, which is impossible for low end LED desk lamps to be equipped with expensive but indispensable optical components.

There’re rating systems to evaluate the discomfort from glare – Visual Comfort Probability (VCP) developed by IES and the Unified Glare Rating (UGR) developed under the aegis of the CIE (Commission Internationale de I’Eclairage).

IES recommends that office lighting systems should have a VCP of 80 or greater. We suggest the UGR value of LED desk lamps to be limited to 19 or less.

But these suggestions are meaningless as virtually no manufacturers will do complicated simulation and evaluation of psychological direct glare from LED desk lamps.

The most critical quality parameter of such a visually demanding lighting system remains uninformed to consumers.

e. Flicker

The flicker phenomenon is in fact directly associated with the industry’s focus to produce cost effective LED lighting products.

Flicker in LED lighting is typically of the imperceptible type which is the invisible modulation of light at frequencies above those at which flicker is perceptible (visible flicker, generally within the range 3-70Hz).

Flicker is caused by the temporal variation or ripple in the power supply (in the industry it’s more commonly called a driver) to the LEDs.

This ripple may be reduced by using an electrolytic capacitor or equivalent electronic component as an energy storage component to bridge the fluctuation in the instantaneous input power.

However the LED lighting industry is moving toward simplifying the LED electronic circuits for reducing the manufacturing and maintenance costs as well as improving design flexibility by eliminating bulky electronic components such as capacitors, rectifiers and transformers.

And because of this we see more and more slim and compact LED desk lamps on the market.

The truth is that as of this writing there’re no effective alternatives to constant current drivers which use a capacitor across the diode bridge for reducing ripples and alleviating flicker problems.

The simplified LED driver solutions such as linear drivers and driver-on-board designs do significantly reduce both the cost and form factor of LED lighting systems, but they sacrifice some key performance parameters with one of them being flicker removal.

Long-term exposure to invisible or imperceptible flickers may cause malaise, headaches and impaired visual performance.

f. Low CRI

Color rendering index (CRI) is a quantitative measurement of how the color reproduction of a light source compares to a reference light source.

High CRI LEDs reproduce colors in an appealing and natural way. Low CRI lighting leads to loss of color fidelity and may cause eye fatigue.

The Energy Star V2.0 requires the average color rendering index (CRI Ra) of indoor luminaires to meet or exceed 80. For reading, writing and other visually strenuous works, it’s highly recommended that the CRI Ra should be greater than 90.

Nonetheless, some manufacturers were found in the aforementioned quality inspection case to have used low CRI (<80) LEDs. We have no expectation that high color rendering LEDs (CRI 90) will be widely used in LED desk lamps because these LEDs are expensive.

Ironically, the obsolete incandescent lighting has an excellent color rendering ability (Ra greater than 95).

Is There a Product that Doesn’t Adversely Affect Your Eyesight?

We can’t be looking backward to the past and use the extremely inefficient but healthy incandescent bulbs for desk lamps.

LED lighting is theoretically viable for task lighting. It’s just that too many consumers and manufacturers are crazy to reap the utmost economics of the new technology.

Practically it’s difficult to find an LED desk lamp manufactured with eyesight protection in mind. Do not simply look at the price tags if you really care about your or your kid’s health.

If you have trouble finding a high quality LED desk lamp, OLED lighting is your safe resort. OLED lighting features superior color temperatures and excellent color characteristics.

Unlike LEDs that produce high intensity light with an unpleasant sharpness, OLEDs are surface emission light sources that use thin layers of organic semiconductor material to generate a soft, natural and glare-free light.

The organic lighting technology eliminates the health risks associated with other artificial light sources such as blue light, ultraviolet (UV) or infrared (IR) emission.

At the moment OLED desk lamps have a very low market penetration and are 5-10 times more expensive than a moderately priced LED desk lamp, but it’s definitely worth the investment.

We all know health is the greatest wealth, and yet health is often not valued till health problems come. Do not let low quality lighting steal your greatest wealth.

How many lumens does the table lamp need?

Since eyes vary with age, it makes sense that as your eyes get older, you will need more light to read by.

The eye’s need for more light to read by increases 1 percent a year. When you’re 10, you can read by 40 watts or hardly any light. By the time you’re 60, you need around 100 watts.

As brightness is measured in Lumens, the following will help you choose a bulb with the wattage (or equivalent wattage) that you need.

  • 40 Watts: Look for at least 450 Lumens
  • 60 Watts: Look for at least 800 Lumens
  • 75 Watts: Look for at least 1,100 Lumens
  • 100 Watts: Look for at least 1,600 Lumens

That being said, keep in mind that too much light or glare can be just as bad as too little light.

When light glares from highly reflective surfaces, it’s fatiguing and especially disturbing for older people with cataracts and retina problems.

So if bright light gives you grief, use a shaded lamp rather than a desk lamp to cut glare and moderate light.

Light in a warmer color temperature will also be easier on your eyes than in a cooler color temperature.

But all in all, when considering the right light for your eyes, remember: your eyes will tell you what they want. If the light isn’t comfortable, they will show signs of fatigue, like burning, redness, brow-ache, headache, or squinting.

Are LED desk lamps good for the eyes?

At present, most work or study has to be done at night, so a light that can focus a lighting shade on the book or device you’re working on is prevalent these days.

As for desk lamp, LED desk lights become the first choice of most people instead of incandescent light or halogen lamp because of high illuminance and fewer eye harms as advertised.

Though they know reading or working on computer for a long time under dim light is easy to make eyes discomfort and even red or fatigued, people are also concerned about a question whether the LED desk lamp can cause eye problems.

Actually, whether LED desk light is bad or good for your eyes depends on what LED light you have and how you use it.

A real high quality LED desk light itself is not harmful to your eyes

There are many LED desk light manufacturers in the market and claim that their LED desk lamps are eye-protective.

A real good eye-protective LED desk light should be equipped with the following features:

  1. No flash or flicker;
  2. No infrared ray or ultraviolet ray;
  3. No electronic wave or radiation interference.

To judge a LED desk lamp whether it is good or poor, you also need to consider some other factors including spectrums, color rendering index, illumance and color temperature. You can find those parameters in a product specification.

Though you may choose a desk light that should be eye-protective, some people are also afraind of using LED light because LED eye-protective lamp is related to blue-ray technology.

The blue-ray belongs to Optical Damage. In fact, retina light adaptability is poor when blue ray is within 400-500mm but become 2~3 times stronger when blue ray is within 450`480mm.

LED peak spectral emission commonly ranges from 450mm to 480mm.

therefore, the LED light is not harmful to your eyes as long as it works normally.

Among so many LED lights, you should first of all choose a real eye-protective LED desk lamp.

Use it properly to avoid potential harms

LED desk lamps are widely used not only for businessmen but for students.

It is harmful to read or work under a lighting shade which is too bright or too dim. The illuminance is up to the light itself but also related to the way you use it.

Many people become confused that sometimes eyes become red or fatigue after all day long learning or working though they’re using a real eye-protective light.

That is because they’re using it in improper way.

So, how to use a LED light properly and protect your eyes?

1. Placement of the light
When you’re about to reading or working on computer, you’d better put it in front left of the table for fear that your right hand blocks the lighting.
2. Light types
You should choose a suitable lamp type that won’t flood light directly to the eyes. You can fix the light in a right view or buy one with an extra light cover.
3. Keep background light on
Some people prefer to turn other lights off when starting using LED light for reading or working, but that will make illuminance difference greater between desk light and background light, which will invoke larger pupillary constriction and make eyes tired, even short-eyesight.
4. Avoid glare of computer screen
If you have to work on computer, you’d better let the desk light illuminate the computer screen forward and backward to supply enough lighting for your eyes. Besides, don’t sit back to the window. The sunlight will exposure to the screen and reflect to your eyes, which will be bad for the eyes.

No matter you have to spend much time working on computer or learning at night, a real high quality LED light can protect your eyes from red or fatigue.

But your improper usage of desk lamp will also be harmful to your eyes.

So, you should choose a high quality LED desk light that can really protect your eyes and use it properly.