
Eye Strain from LED Backlighting in MacBook Pro (2008) - walterbell
https://discussions.apple.com/thread/1677617
======
pflanze
I think this probably concerns many more people than are aware of it. I could
live with the flickering but I live better by doing what OP did, set screen
brightness to max, on all of my laptops and external LCD screens. I then use
redshift (I'm on Linux)[1] to dim the screen to the desired brightness, i.e.
absorb the excess light in the liquid crystal layer. Sadly this does appear to
lead to some loss in brilliance and color quality, but it's not too bad, and I
like that I never have to see the flickering.

I know someone who puts a foil based filter in front of the screen, that may
work somewhat better, I still haven't tried that myself.

I find it frustrating how almost all LED lighting installed in the UK is PWM
based (if dimmed), or otherwise flickering (AC), too. And it's just a question
of consumer expectation: if you buy an LED light bulb in a standard shop in
Switzerland, it doesn't flicker, if you buy one in the UK, it does. Both bulbs
use the new LED filaments, you can't tell the difference from looking at the
bulbs, the difference is in how the power supply in the base of the bulb
works. I opened up one of the Swiss bulbs and it had a proper switched-mode
power supply (using a switching frequency probably in the 100 KHz range); I
saw a video on Youtube by someone who opened up one of the UK ones, and the
power supply was based on current limiting via capacitors (and then a
rectifier), which leads to a flicker at twice the AC frequency (hence 100 Hz).
There's going to be a cost difference of £1 or so, the Swiss consumers are
apparently ready to pay for that, the UK population not (or the UK shops
possibly pocket the savings).

[1]
[https://en.wikipedia.org/wiki/Redshift_(software)](https://en.wikipedia.org/wiki/Redshift_\(software\))
(actually still using the command-line variant of an older version, e.g.
"redshift -b 1 -g 0.9:0.9:0.9 -l $POS -t 5500:4800")

~~~
yardie
Could this be a difference in the dimmer. I’m in the US (120V vs 240V) and I
had research carefully what dimmers were compatible with the dimmable LEDs in
our flat. Sometimes the dimmer would hum, the LEDs would squeal, or they would
go from 0 to 100% with 20% dimming.

Most LEDs are made in China and I doubt the Swiss are getting a specially
manufactured ones. But old, incompatible dimmers are definitely a thing.

~~~
Zak
It's not the LEDs themselves that are a problem there, but the driver
circuitry in the "bulb"[0]. There are a fair number of these being made in the
US and Europe, not just China. Significant numbers of LEDs are also made
outside China - Cree manufactures LEDs in both the US and China; Nichia
manufactures LEDs in Japan.

[0] Bulb is not really an accurate term here. Maybe bulb-replacement?

------
notadoc
Not sure about the backlighting or a post from 2008, but on the topic of eye
strain... the diminutive text sizes and obsession with low contrast throughout
the redesigned bleached UI certainly causes me eye strain. I've heard similar
complaints from others, and about the new system fonts and anti-aliasing too.

~~~
exikyut
I wonder if turning on accessibility features would help.

------
geofft
Title should have (2008). (Also is there some current relevance that I'm just
out of the loop on?)

~~~
ebbv
Nope, as far as I can see there is no reason for this to get posted. Seems
almost like OP is trolling for karma because it has a controversial title and
links to Apple.com.

~~~
walterbell
The thread is 164 pages long and active through 2017.

~~~
ebbv
So you think we should read 10 years of babbling by cranks who don’t like LED
backlights on a support forum?

~~~
walterbell
A statement from Apple would be best, for an issue that has affected customers
for nine years.

PWM backlighting was introduced on the iPhone X and is affecting some
customers.

edit: s/backlighting/OLED dimming/

~~~
aceoflolo
Why does the iPhone X need backlighting when it has an OLED screen?

~~~
walterbell
Maybe someone who knows more about AMOLED panels can comment about the role of
PWM? It seems to be something other than brightness control, the article at
[1] says:

 _At any level of brightness, modulation with a frequency of approximately 60
or 240 Hz is present ... It can be seen that the amplitude of the modulation
is not very large at the maximum and near to it brightness, as a result there
is no visible flicker. However, with a strong decrease in brightness,
modulation appears with a large relative amplitude, its presence can already
be seen in the test for the presence of a stroboscopic effect or simply with
rapid eye movement. Depending on the individual sensitivity, such flicker can
cause increased fatigue. "_

[1]
[https://translate.google.com/translate?act=url&depth=2&hl=en...](https://translate.google.com/translate?act=url&depth=2&hl=en&ie=UTF8&nv=1&prev=_t&rurl=translate.google.com&sl=ru&sp=nmt4&tl=en&u=http://www.ixbt.com/mobile/apple-
iphone-x.html)

------
KirinDave
To be honest, I'm skeptical that this is a universal feature of the MacBook
line. I don't own one of my own (I'd never!) but I use one for work and I can
see those effects as well if I know how to look at them (I used to have a DLP
and it was easy to reproduce the rainbow effect).

The flickering on this LEDs is not really any different from the CCFL flickers
before.

------
sschueller
Interesting, but don't CCFLs also "flicker" just at a much higher rate?

~~~
exikyut
Yes; I can see the flickering on my CCFL-based ThinkPad, but it's thankfully
not annoying.

~~~
walterbell
Detailed comparison of CCFL & LED flicker:
[https://www.infobyte.hr/blog/134/ccfl-vs-led-screen-
backligh...](https://www.infobyte.hr/blog/134/ccfl-vs-led-screen-backlight-is-
led-really-better/)

CCFL PWM flicker:
[https://youtube.com/watch?v=RHlvgo6b_2s](https://youtube.com/watch?v=RHlvgo6b_2s)

LED PWM flicker:
[https://youtube.com/watch?v=84OCOX9O3PE](https://youtube.com/watch?v=84OCOX9O3PE)

~~~
exikyut
YEOW. OUCH.

I...... I am very glad I'm using a CCFL laptop. This is like going back to
evil 60Hz CRT flicker!!

I've just accepted I might need to rip out the LED driver board in a future
laptop and replace it with my own design. Hopefully not, but if that has to
happen then okay.

Thanks for the reference to the comparison, that was also very interesting to
go through (and bookmark).

------
antirez
Just tested my Macbook Pro (2016 model) with a 120 FPS camera and apparently
there is no flickering in the display, however the keyboard backlight appears
to use PWM.

~~~
systoll
Same for 2017.

I think a lot of it is down to the usage scenario, but the keyboard is the
most obvious ‘flickerer’ I’ve seen... anywhere.

A screen like that [or a mandatory keyboard backlight] would be an instant
dealbreaker to me.

------
dmitrygr
> My research into LED

> technology turned up

> the fact that it is a

> bit of a technological

> challenge to dim an LED.

This is complete nonsense. While pwm can indeed be used, many of the nicer LED
drivers are actually variable current. While adjusting the voltage directly
indeed does not work as expected for LEDs, a constant current driver does
indeed produce a constant brightness. Varying the current varies the
brightness. Only the cheapest displays and lighting installations use pwm for
brightness control.

~~~
modeless
... and many car/truck taillights. I think PWM taillights should be illegal.
The artifacts are distracting.

~~~
ChadMoran
This, so much this.

I have nystagmus which means my eyes move uncontrollably. Primarily on the
horizontal plane. While my brian compensates for this and I don't see a moving
image anything that uses PWD flickers very, very badly.

PWM tail lights are THE ABSOLUTE WORST for this condition. Not only do I see
it on the source but I see it on anything the light projects onto, it's
horrible.

~~~
exikyut
Wait. Contemporary nystagmus == saccades?

I haven't tracked the cause down yet - I know it's a nerve issue of some kind
- but sometimes my jaw, arms or eyes (yup) can occasionally jump. My jaw and
arms jump when I'm nervous (or have a buildup of too much nervous
energy/excitement), while my eyes jump when I'm trying to focus on something
too hard, they drift, and I try to course-correct too hard. (I think half my
brain is aware of the drifting, but the other half, the part that would make
the fine motor movements to keep my eyes locked, is happily whistling away
blithely in a corner somewhere.)

When _my_ eyes jump and I overcorrect when I fail to re-point them where they
need to be, I usually have a second or two where I'm not technically blind but
I need to let my eyes refocus and remember their purpose in life (if you will)
:P

I always thought this was nystagmus (read the term online one day and went
"!!! that's what it's called!")... but now I wonder, is what I'm dealing with
something else?

(An aside: I'm really, really bad at tracking moving objects in space. If
someone else is holding onto something and I'm expected to look at it, I have
to hold it instead. No other alternative.)

------
ksec
I wish there is a Standard where ALL LED, doesn't matter whether they are used
in lighting, backlight, keyboard or what ever, small or big, to be flicker
free. Or Extreme High Frequency.

There are increasingly more shops, shopping mall, or whatever places it is,
and Monitor, billboard etc, especially in China or made in China where culture
are more price sensitive, using cheaper LED, so they could say they are
governmentally friendly. ( There are also some government incentive in doing
so ). And INSANE environmental groups which forces everyone to switch to LED.

Many of these LED has flickering issues, that some people dont have a problem,
some people are little annoyed but are fine with it, or some minority like me
which needs to run away or I would puke or sick.*

I tired LED lighting once, it started have flickering issues two years in. It
was very minor, but enough to irritate me. I have since switch back to good
old light bulb.

*I have also discovered those who are sensitive to these flickering issues are also likely to be latency sensitive, as discussed in the computer IO latency and web latency.

~~~
pathartl
I've always found LED Christmas lights to be the worst offender here. Most of
the time this issue can be solved by buying quality LED bulbs and using the
correct dimmer, if you have one.

Walmart had 100-bulb LED Christmas lights on sale for $6 a string. This is
just around the price of non-LED strings, however these are 120v rated LEDs
that run right off the mains with only a fuse to protect them. Needless to say
these things are tied to the 60hz phase. Since these were being put on my tree
this year, I decided to do something about it. A simple full bridge rectifier
fixed most of the issue. I think now the phase on the string is more around
120hz which is much easier on the eyes.

I can still see the flicker, however it's not nearly as bad. I believe the
thing that would fully rectify the issue (see what I did there) would be to
throw a capacitor in the circuit to further smooth out the DC supply. Really
it comes down to the idea of a diode; current flows in one direction. In an AC
circuit, it flows both directions. Convert it to DC and smooth the supply out
and you're using just as much energy without flicker. Of course this ends up
costing more if the manufacturer were to implement, so there's that.

I really just want DC throughout the house.

------
gargravarr
This is something I noticed as well - I upgraded from a PowerBook G3 to a
PowerBook G4 in 2009, and then to a MacBook Pro in 2010. I bought the fastest
non-unibody machine available, a 2.6GHz A1260. It lasted me very well, five
years of daily use before I upgraded. However, I began to notice the backlight
issue. I'm a writer in my spare time, so staring at a screen is an
occupational hazard. With a CCFL screen, I can stare at it all day at a
comfortable level. With an LED screen, full brightness is astonishingly
bright, so you have no choice but to use it dimmed. I found I could only go an
hour or two at a time in front of my expensive MBP, and for a long time I
couldn't figure out what it was. I considered going back to the G4 many times.

It was only after I started using an LED-backlit external screen that I
spotted the connection. Apparently I'm a little more sensitive to PWM than
average, although perhaps not as much as the OP of the Apple thread. At worst,
after about 45 minutes, my expensive LED-lit monitor would give me migraines
when dimmed, which the laptop didn't.

Either LED technology has improved or I'm no longer sensitive to it, because
my current Clevo laptop is LED (as is just about every screen on the market
now) and I'm okay using it for long periods. I had to learn to tolerate the
external screen on maximum brightness in a well-lit room for a long time.

It's annoying and certainly not ideal, but I can't blame the manufacturers.
CCFLs are power-hungry and toxic, and were always going to lose against LEDs.
The technology is easily superior but lacks finesse. It only affects a
minority of people, which is probably why it quickly supplanted CCFL - either
no study picked it up, or it was such a small number that it could be ignored.
I wouldn't want to keep using CCFLs but I wish they'd figured out a better
solution before bringing LEDs to market.

------
IdontRememberIt
To manually check if the PWM has a low frequency: put your finger in front of
the screen (or the led lamp you want to test), and move it quickly to describe
a paper fan (V). If you see a stroboscopic effect, the frequency is too low.
=> The screen is not flicker free or the screen brightness too low. This is
only a quick test not a bullet proof solution.

------
alt_f4
It is high time for an OLED dispay on the MacBook Pro. And not just on that
horrible touchbar gimmick.

~~~
dijit
OLED has horrible burn in. For phones they’re doing incredible mitigations but
the fact is that the screen isn’t on with static elements for 8hours+ solid
each day.

~~~
duckfruit
I'm not so sure that's true. The mitigations they're doing seems to work very
well for all sorts of form factors. I've been using a dell UP3017Q OLED
monitor as my main display for most of last year and haven't had any issues so
far whatsoever. It's simply the best display I've ever used. Even for my LG
OLED tv, which I've had for a couple of years hasn't exhibited any image
retention issues at all, despite watching a lot of news with scrolling
headlines and logos. I wish OLED monitors would become more generally
available since they're far, far superior to LCDs but for some reason apart
from a limited run of the Dells and some short lived laptop models they're
pretty much nonexistent.

~~~
alt_f4
There's the ThinkPad X1 Yoga with an OLED display. From what I've heard, the
thing is absolutely stunning and a pure joy to code on with a black / dark
editor theme. It just emits way less light than the equivalent LCD setup.

------
derefr
Question: this is a problem because the LED array (as an LED backlight or an
OLED display is) all flickers _in synchrony_ , right? Would it still be a
problem if each LED in the array was hooked up to its own delay line with a
randomized-at-the-factory value?

~~~
monochromatic
That would probably help some. Really, they should just flicker faster.
There’s no reason not to do PWM at a kHz or 10, and nobody is going to see
that flickering.

~~~
CamperBob2
Actually, there is a slight problem, in that many people will be able to hear
the inverter.

It's tough to make a completely silent inverter that works near the peak of
human hearing sensitivity. It can be done, but it's likely to be more
expensive.

Going all the way to 20 kHz+ is probably the best strategy. LEDs can be driven
well into the MHz range, but if you go too high, RF emissions compliance
starts to become a problem.

~~~
monochromatic
That’s a good point. Call it 50 kHz to deal with people who have abnormal
hearing response.

------
RichardHeart
[https://www.notebookcheck.net/](https://www.notebookcheck.net/) always tests
for PWM and otherwise has the best laptop reviews on the planet. Example of
PWM test: [https://www.notebookcheck.net/Lenovo-
ThinkPad-X1-Carbon-2017...](https://www.notebookcheck.net/Lenovo-
ThinkPad-X1-Carbon-2017-Core-i5-Full-HD-Laptop-Review.229966.0.html#toc-
display)

------
7ewis
I use a MacBook Pro all day at work, then at home in the evenings. I can't say
I've ever had an issue with eye strain.

Over the years I've used many different models too.

------
NateyJay
The PWM backlight driver frequency should be much higher. This kind of effect
is only perceptible at sub-kilohertz LED switching. The LEDs themselves are
happy to be cycled into the megahertz, so the only reason for this on the
Macbook is poor electronic design. A low frequency does provide reduced cost,
slightly higher efficiency, and reduced auditory/RF noise emissions, but
visual effect has to be top priority.

~~~
monochromatic
Yep. I wonder if you give up some small amount of power efficiency at higher
frequency, but it shouldn’t be much.

------
twobyfour
It's evident that this sensitivity is pretty rare. But with essentially
everything LED-backlit these days, living with that sensitivity sounds
hellish!

~~~
KirinDave
Most people can see these effects if they know how to look for them. Most
"sensitives" are folks who accidentally figured out how to see them.

It's really not at all clear that they possess some kind of higher clock rate
for sampling optical images.

~~~
wlesieutre
I've noticed this with some LED light fixtures in people's houses before and
deliberately don't mention it because once you see it you can't unsee it.
Particularly evident on things like running water in a bathroom.

I can deal for a few minutes, they have to live there!

~~~
KirinDave
Personally, I think this is like when kids start sticking their tongue through
the slit of a Halloween mask until they cut it. It's just something you can
choose to stop doing but people can't help themselves.

------
noncoml
Not sure if it is the OLED, but after switching from iPhone 7 to iPhone X I
get terrible headaches when trying to watch Netflix on my phone before I go to
sleep.

~~~
walterbell
It's a similar issue. The Samsung display in iPhone X flickers at 60/240Hz due
to PWM brightness control of the OLED. This is more noticeable to the human
eye at low brightness. Options are to use the device at higher brightness
level or switch to iPhone 8.

[https://forums.macrumors.com/threads/eye-strain-while-
using-...](https://forums.macrumors.com/threads/eye-strain-while-using-
iphone-x.2085427/page-31)

[https://news.ycombinator.com/item?id=16088173](https://news.ycombinator.com/item?id=16088173)

~~~
noncoml
It explains it, thanks. It’s a deal breaker for me so if I could I would go
back to 8plus.

~~~
walterbell
Apple will likely prefer a refund/exchange to paying for customer medical
bills.

------
amelius
Isn't the solution to simply turn up the frequency of the flickering?

~~~
Zak
That would be a solution, however flicker-free dimming for LEDs is not
difficult. Linear regulator chips are cheap, but inefficient. Switch-mode
power supplies cost a little more. Both are mature technologies any electrical
engineer should be familiar with.

~~~
monochromatic
LED light output isn’t linear in power input though. PWM allows you to drive
the LED in its most efficient regime no matter how much brightness you want.

~~~
Zak
Efficiency tends to decrease with current. It is rarely more efficient to run
higher current and PWM than to simply run lower current.

It is, however often _easier_ in terms of circuit design.

~~~
monochromatic
That’s interesting, I thought there was an optimal range. Do you have a link
with more info?

~~~
Zak
Well, I can offer an _example_. This is a test of an LED using a bench power
supply. In this test, efficiency drops every time current is increased,
without fail.

[http://budgetlightforum.com/node/51693](http://budgetlightforum.com/node/51693)

------
nukeop
Apple displays are always poor quality.

