Here's the thing - some of us DO experience problems with artificial lights that is NOT related to PWM.
In my company's new office, they chose to use exclusively "eco-friendly" lighting, which is a combination of CCFL (with which I don't have a problem), high-intensity fluorescent (very painful), LED (also very painful) and regular fluorescent (acceptable, but still overbright) lights.
In the areas with high-intensity fluorescents, my eyes IMMEDIATELY become tired, and if I attempt to READ anything - books, magazines, the screen of my laptop which has never given me problems in the years I've used it - I experience eyestrain and headache within a few minutes.
In the areas with CCFL, my eyes are ok if I use a good source. We have a workroom where we build servers and network stacks, and I can be in that room for quite a while without problem. The only issue in there is TOO MUCH light, as they put CCFL cans every couple feet, 9 lights in a room that is only 15x15 which is maybe 4 lights too many.
In the areas with regular fluorescent, my eyes are ok but again it's TOO BRIGHT. They put mirrors, reflectors, and doubled-up light fixtures everywhere. Instead of the normal distribution of light, there's maybe 50% too many fixtures so my eyes quickly get tired.
And in the areas with LED, I literally cannot focus. This is not made up - MANY people have noticed this. The new LED streetsigns that businesses put up to advertise their wares have actually been the subject of lawsuits due to the fact that people are blinded by them, and there are rampant problems in places that have switched to them exclusively.
I suspect that this problem will only get worse - right now it's a very small minority of people affected, but as these lights become more common it will be a much larger percentage and organizations will be forced to act.
For me, a combination of the following has worked out "ok", but not perfectly:
1. I only go to the office every other day most weeks. This week I have to go in 3 days in a row and it's really wearing on my eyes. I'm very lucky that my employer is ok with a 3-day in-office schedule per week, and that I was able to arrange Monday/Wednesday/Friday. The days at home really give my eyes a break most weeks.
2. I have removed the high-intensity fluorescent over my desk and use natural light from the side through a translucent shade as my primary light source. This is imperfect, since 6 feet behind me and 6 feet to the right of me are MORE high-intensity fluorescents, but if I wear a visor the glare from those ones are minimized.
3. I wear Gunnar-tinted glasses over my contacts when I have to be at my desk for long periods. This further cuts the glare. When I walk around the office from light source to light source, the gunnars really help as well. I am currently custom-ordering some gunnar-tinted "computer glasses" optimized for my screen distance (2-4 feet) and tinted with Gunnar (and Crizal Sapphire if I can double up!)
But I still suffer. 9 months ago this wasn't even remotely a problem as I worked under old-style "white" fluorescents.
Is PWM a problem? Absolutely. Even under the best lighting, screens with intense PWM are a problem. But the laptop I am using right now causes me no eyestrain, and it has PWM and LED backlighting.
There is SOMETHING about new LED's - whether it's their light spectrum, their transmission matrix, or SOMETHING - that makes this problem much MUCH worse for most of us.
I'm glad eliminating PWM fixed your problem - it's the easiest thing in here to control! A new monitor solves it! Our other problems are much harder.
Yes, and no in that order. The overall effect is a dimmer screen, but not everyone perceives it the same. 99% of the population just sees a dimmer screen. 1% can see flicker, and maybe 10% of that 1% is in this thread and sees it as pain or strobing.
Everyone has a different sensitivity level.
PWN on a CCFL is less harsh because the light "fades" instead of being instantly off. Kind of like instead of a strobe light you take a flashlight and wave a translucent piece of plastic in front of it. The light never goes OUT, but gets dimmer and brighter. Much less painful.
Some people in this thread claim that the MBP and the latest iphone & ipad dont use PWM. Personally even if i keep the iphone at full brightness, while i feel it is better than having the backlight lower than full, i still get a strange headache. I have tested the iphone and MBP at full brightness even after a long time of adequate rest.
What i can say is that if at full brightness, personally, my eyes recover much faster, but still it makes me think twice to use the phone or laptop. This for me makes the devices unusable. With the older apple laptops (ccfl backlight) i could work without the slightest discomfort for many hours.
I have also tested the same way Lumia 920 and SG3 and i get the same discomfort (i.e. at full brightness and after adequate rest).
Do you also imply that if used at full brightness the eyes in due time get accustomed to the display since there is no flicker?
I can appriciate that you have problems with office LED lights and other lights. You say that your laptop with LED and PWM does not cause problems. This is exaclyt to my point about that we should be as scientific as possible. You should measure the PWM flicker frequency with a camera or oscilloscope and if possible, find out what kind of LED's the display has. If the PWM frequency is the same as with other PWM's that cause problems to you and if the LED light spectrum and intensity is aboutu the same as other LEDs, then it's a strange thing and we should continue to research this, to find another reason why some displays cause eye strain. But you complain about too bright lights, mirrors etc. I'd say that it's quite atypical. Now, this whole problem with PWM is atypical, but the point here is sensitivity to LCD displays, not general atypical sensitivity to bringht lights and office LED lights.
I mean, there are all kinds of problems that people have with their eyes, but those might not be related to the same issue that this discussion is about. As I've understood, many are like me, no other problems with the eyes, except the sensitivity to LCD PWM flicker.
If we want to draw manufacturer attention to this, we can't have people with all kinds of eye problems reporting sensitivity to LCD's, though as problematic their cases might be.
I don't see any flicker, not above about 80Hz. So I do percieve the PWM dimming as dimmer and do not see any flicker, but my optic nerve does register the flicker, which is probably the reason it makes my eyes red and ichy.
I don't think that Christmas lights flicker, as I think they would need to have the PWM for that, but I'm not sure. No data on that.
I have GS3 and since I put the brightness permanently to 100%, I have no problems in using it say one hour or more during the evening, when I'm watching the TV and browsing Facebook etc.
Though, I have not tried to read a book from Kindle the brightness at 100%. So I'm not sure if that would cause problems. But I would think that then it's a more typical issue of switching between looking a bright light and then looking around the room. As such pretty unnatural situation. You seldom have this problem in nature, that your eyes need to constantly adjust between brightness and darkness.
Sorry, I’m thinking out loud here…
Would it be also safe to presume then that people who perceive the flicker also perceive a greater brightness, however the total amount of light entering the eyes of both groups of people would be the same? I would guess that if this was a light intensity issue that the non-perceivers would be in a worse position?
The focus issue, and temporary blurred vision, I’ve noticed appears on screens not only dimmed by PWM and appears on a mixture of AMOLED, AMOLED pentile, LCD, TFT, IPS screens, but seems restricted to LED backlights, but I must stress not all LED backlights, there are LED lit screens that I do not suffer with. There’s too broad a mixture for this to be ‘just a PWM’ issue, or just a ‘blue light intensity’ issue I am experiencing, I think Gurm is correct in saying that there’s ‘something’, perhaps related directly to a problem LED type, it’s this ‘SOMETHING’ as Gurm puts it that could help identify potential problem causing products. I don’t doubt that most of us will benefit from avoiding PWM products, or reducing blue light, but I’m not convinced it’s the only underlying issue for some of the sufferers on here.
I think it could come down to a particular manufacturer(s), or a particular manufacturing process/technology.
I would like to chim in here I love that you are all having such a great debate about PWM VS. Spectrum/wavelength. Great inputs on scientific data, I have to reflect on the fact that we are not scientists who have an understanding of light in it's true scientific form so it does not seem possible for us to form a hypotheses on the direct cause of anyone's issue here. Also, if you read through the posts its very interesting how some people can tolerate this or that and there is no baseline for accuracy in our findings. When you begin to research medical conditions that cause light sensitivity you will find no end in your search as well however the only common theme here is that everyone is bothered by LED backlighting, so why is that? Yes, we are sensitive however why is the only constant result LED light? We'll there is something about the technology that bothers us, we cannot say for certain it is PWM only or spectrum only and the reality of why it is so confusing could be that they are both contributing factors. My pellet stove fireplace flickers and gives me a headache while viewing through the glass door as well, fire is full spectrum light. It's not as bad as an LED light however add flicker AND blue light and I am one sick dude!
Here is my experience with spectrum VS. PWM/HZ: I cannot tolerate any of the monitors I have tried at 100% brightness (Including several Apple products), in fact at that brightness I get so sick I cannot stand on two feet and need to lie down in minutes. For me I can tell that the brightness and whiteness/blueness of a light is part of my problem, high pressure sodium lights are also more intense than regular fluorescent lights for me because they are so bright and white.
I would also like to state that each device is not the same, the technology can be of lesser or greater quality, some LED lights are at different spectrums. There is the possibility there is more harmful blue light in one light VS. another, this is not regulated in any way!!!!!!!! An LED light at 5000K is much different than one at 3200K however both make myself very sick.
In addition to this there are scientific reports starting to pop up showing LED lights are permanently damaging our retina, one from Spain was posted earlier in this forum. Also, in my work with an Anti-glare coating company I have heard their scientist believes from her testing on animal retina's she is close to showing scientific data that LED light can damage our eyes.
The truth is this technology isn't proven yet and there were no epidemiology studies before we started using it, such is the way of the world and big business at the expense of the consumers health.
My prediction is that there will be a solution with either a coating for glasses for us who are sensitive or the technology will change in the next 5-10 years due to greater discomfort from the general public as a whole during a massive adoption of overhead LED lighting in our homes and business's.
David i think you are right.
As mentioned before. From 2008 onwards
Problems with CRT i.e. iMac
Then 2005 powerbook LCD so had buy new machine.
LED 2008 macbook pro, not bad all day working very minimal effects i.e. red skin / prickly slight dry eyes.
LED 2010 macbook pro more of a effect Prickly skin red face dry eyes.
LED 2013 macbook pro Retina Very bad on all accounts, sent it back.
LED macbook pro Non Retina Bad to the point of sending this one back.
Whats was the screen technology in the 2008 model? Which i can only use.
( All this with all wifi turned of as it give me headaches and dizzy spells )
Ive just recently calibrated both 2010 and 2008 screens using a Pro spider a tool used by photographers to get a perfect screen. which on both screens dialled out a lot of blue from the spectrum. So we shall see what happens.
Please look into crypto-chromes, found in humans, help us detect light and therefore have a vital effect on our secretion of melatonin, the hormone that plays an important role in bolstering the immune system.
GKphone, it sounds like your getting skin reactions? That's interesting and something we have not covered much here. I have read a little bit about that during my searches, there are a lot of people out there who cannot even enter a store because their skin breaks out in rashes from fluorescent lighting, I have not found much info on this and LED lighting yet.
Hard to find any link to screen dermatitis and LED monitors, I was actually wondering if LED would be better for this condition. There are so many manufacturers stating that because LED lighting is a "Solid state" lighting it will not cause eye strain and I was wondering if this was also a perception with dermatitis issues that is untrue.