2

With recent research suggesting melatonin levels linked to blue wavelengths of light via the melanopsin, a plethora of phone screen dimming apps have been released.

My sister claims they can damage the screen: they flicker the LEDs more than the manufacturers brightness controls. Is such a claim true? Can they really damage the screen?

5

The short answer is NO. Unless you try to go over default brightness (which could potentially burn the LED), your screen leds are desgined for changing brightness and colors.

Leds work differently than most lightbulbs and flicker has much smaller effect on them.


Longer version of explanation

First of all, leds do not "flicker" the way fluorescent light bulbs do when they glow. LEDs glow by steadily releasing energy (photons) from electrons whereas most other light bulbs rely on heat to release light.

  • Incandecent - These bulbs are literally a wire that's being heated and the light from that same wire.
  • Fluorescent tubes - A bit too complex to explain in once answer, but in short, they rely on electricity to heat (basically) a wire that heats gas which in turn activates phosphor emitting the light.

A point to note here that both lamps heavily rely on heat to shine and in turn, breaking current could result in heating elements getting damaged

  • LEDs light is emitted a little differently. Diode (the glowing bit of LED) consists of positive charged and a negative charged plates. When affected by electricity the charges are forced to mix, which causes electrons to release energy (light).

Flicker on most heating light bulbs damages their components

Now the reason I say LEDs don't flicker the way other light bulbs do is because other light bulbs mostly heat-up and cool rapidly during each flash. In addition to that additional heat may be inflicted on the heating component during a short reverse of phase occasionally happens on power breaks. To summarize, flickering causes the heating component to crack or burn out on standard light bulbs.

LED light emission doesn't rely on heat, also, if current is reversed (like it unusually gets on power cuts or breaking current) on LED it doesn't simply shine the way most other lights do - as in fact it pulls the positive/negative charge away from each other preventing a glow.

Flicker on LEDs

As far as i know LEDs can only flicker when electric current is too low to maintain constant mix of charges between the 2 semiconductors, which would result in burst exchanges every time diode is "charged" with enough electricity.

Flickering as well as dimming by itself is known to reduce the lifespan of an standard (room-lighting and small) LEDs by 30-60% (according to various sources).

Anyways, phone screens are designed to last while being dimmed and under changing current, so even if your screen suffers it will probably outlast the phone.


Summary

With that in mind an led with lower current might glow dimmer or change color, but the light-stream should remain steady - at least on screens.

If they DO flicker (I could not produce the flicker on 3 of my android devices), they are technically getting their lifespan reduced, but still not enough to matter.

LED screens (with everything they contain) are designed to be dimmable and most apps you see on the market are most likely just exploiting device settings.

Side Notes If you can perceive a flicker it will reflect on your health more than it will on the phone. Be wary of unusual headaches or dry/tired eyes.

Easiest way I found to detect display changes on screen is filming the screen as you're changing the settings. If flickering DOES occur you should see it quite clearly in the video.

  • I know for a fact it is flickering, because if i am in a dark room, and i move the phone quickly, i see discrete areas of light, like rectangles, where the phone was moved through – Jonathan Jun 2 '15 at 23:18
  • I've updated my answer, also, what app are you using? I've got Samsung Galaxy S4, S4 mini and Trend 2 (all different price ranges) I was unable to produce flicker with Screen Filter Module (xposed). – Zero Jun 3 '15 at 10:17
  • The flicker is not noticeable to the human eye, unless you do a trick. Go to a completely dark room, and take your phone, and pass it left and right across your face as fast as you can You will noticed slight discrete squares. If not, your screen may not be dim enough. To dim more: Download the twilight app. Put it on max dimness. Set your phone to max dimness. Now try. Let me know if that works for you. Tested on Samsung Galaxy S6 – Jonathan Jun 4 '15 at 22:13
  • I have tried it, and while the dimming transition was too smooth (fairly distinct steps from dim to bright and the other way around) I did not experience any flicker on dimmed screen in my dark closet - will try my room at night. If you have the option try using 'screen filter' module on xposed framework (requires root). It allows going much dimmer than 'twilight' (almost to the point where screen is too dim to see in day light) and still no flicker. – Zero Jun 5 '15 at 9:07
  • LEDs /can/ flicker... if they are dimmed with PWM instead of a constant-current driver. – nmz787 Jan 5 '18 at 19:16
3

Please note that screen dimming apps apply a filter over the phone's screen. It's an overlay, so I don't think it will cause any damage the screen. But it will decrease the brightness just by applying a filter over your LED brightness (just like applying sun protection in a car window). Some screen dimming apps provide different colors while applying filters like blue, black, yellow etc.

On a side note, do remember that these filter apps does not allow installation of .apk files. So you have to disable the screen dimmer app and then install the app.

  • They could potentially change the filter from pure black to light color over and over and over every other frame, flickering. I know for a fact it is flickering, because if i am in a dark room, and i move the phone quickly, i see discrete areas of light, like rectangles, where the phone was moved through – Jonathan Jun 2 '15 at 23:19
3

As developer of a popular non-profit Bluelight Filter app, we can assure you that you can safely use screen dimming and filter apps without any worries that it will affect your LCD/LED display.

Screen dimming apps work in two ways. One, they allow you to change the screen brightness, just as in your display settings. Brighter screens do burn your screen more, but it should not be a problem as the LCD/LED displays generally far outlive the phone. A bigger concern would be that bright light is not good for your eyes or that brighter screens drain your battery faster.

The second way is to apply a semi-transparent color layer on top of your screen. This has no effect on the LCD display. The reason is that, the video display processor calculates the effective pixel color before setting each pixels color. So if you have multiple semi-transparent layers, it just mathematically works out the color and brightness to be applied to the pixel on screen before passing it on to the hardware pixels. So there is absolutely no extra flicker associated with the screen filter other than what would be associated with the normal refresh cycle of the display.

  • What about serving black Frame a intermittently? Does the Android app twilight do that? It seems to be able to dim the screen far beyond OS brightness settings – Jonathan May 26 '16 at 17:17
  • 1
    No, Twilight does not use black frames. You can get any dimness all the way upto 100% opacity. Just think of a fully black layer over your screen. The brightness setting essentially changes the maximum brightness value of the display. But within that range of minimum brightness to maximum brightness, the darker colors emit lesser light while whiter/lighter areas emit more night. The overlay essentially makes the screen darker. That is why apps such as Twilight is able to give more darkness than what the brightness setting alone could achieve. – PANAGOLA May 27 '16 at 15:29
  • I don't know if you know this but the way that LEDs work and dimming light bulbs work is that they only have one brightness. Any amount of dimming is simply caused by strobing. I've wired them myself. Search YouTube for how dimming bulbs work – Jonathan May 27 '16 at 16:14
  • 1
    Guess we are not talking of LED bulbs here. As far as LED displays such as AMOLED, the brightness of a pixel is proportional to the power applied. In the case of LCD screens, backlit by LED or otherwise, it is the transmittance of the Liquid Crystal layer in front of the backlit that is changed by varying the power (voltage & current) supplied to the individual pixels. – PANAGOLA May 27 '16 at 17:15
0

The answer is YES but this happens only with some phones.

I have a Samsung S5 I used twilight App for a while, and after I uninstalled it I got my screen damaged, a random rectangulars with random colors appears in the screen when I reduce the brightness to the minimum.

The same happened to the phone of my friend after using the same App.

  • That's what happened to my sister – Jonathan Nov 21 '17 at 22:46
-1

Perhaps, they can. My sister ran a f.lux like app (Twilight) for a while, now her screen flickers green, shows scan lines, and shuts off randomly while dimming the screen.

However my friend ran it for over a year and had no issue. Proceed with caution.

I have chosen to use twilight most nights, as my eyes are worth more than my phone screen.

Edit: I wrote this in 2015 -- it's now 2017 and I chose to use screen dimming apps every day since. Well, still no problem, phone runs fine. Not sure why my sister's phone had issues. Out of caution I did delete twilight and started using the built in android blue-light filter.

EditEdit: It's now 2019 and screen dimming apps are ubiquitous on all OS's and platforms, I think it's safe to say they do not damage screens. My sisters phone must have been anomalous.

  • 2
    Why do you think the problems are due to Twilight? Perhaps the screen would have failed even without any screen-dimming app. – unforgettableid Nov 27 '15 at 13:56
  • I'll be honest, I don't know. But it only has the screen damage when the screen is dimmed. It is pure assumption on my part to therefore blame twilight. – Jonathan Dec 4 '15 at 7:13
  • If you doubt Twilight, you can try our Bluelight Filter app. It is tiny, ad-free and does not use any black frames for dimming. – PANAGOLA May 27 '16 at 15:37
  • 1
    Just one note (true for older androids): I don't know exact workings of all smartphones, but older android phones can turn on and work without a screen connected. It would generally take a short circuit or a software failure to force a phone crash (like you describe). This is important because LEDs (btw, not the type that are used in screens) are the only screen components are known to be damaged by low currents, but they still only pass current 1 way and can't cause a short circuit. With that said, if an app caused LEDs to fail, the screen might not work, but the phone would not shut down. – Zero Feb 14 '18 at 8:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.