LCD and your eyes

[JSWolf]

Originally Posted by Cinisajoy

I am going with HarryT. It totally blows my mind how bright some people keep their screens.
I can't count the number of times I have read here that people can't see the screen in a bright room but it is blinding in a dark room because they turn the light way up before going into a dark room. This is both tablets and ereaders and a few computers. I keep my lights as low as I can. My husband on the other hand keeps his screens brighter. I am nearsighted with bifocals. He is farsighted with trifocals.

What I don't get is when some say that they cannot read from an LCD screen because it bothers their eyes and yet on an eInk screen with a front light, they keep the light way too bright. So how is that overly bright front light not bothering their eyes? I think it could be psychosomatic because they think LCD is not good so they say it's not good yet eInk with too bright a light is not good.

[JSWolf]

Originally Posted by Gotadimple

A dedicated ereader is designed for reading at close range with screen graphics that do not cause you to squint, and includes a non-glare surface.

A dedicated eInk reader can very much have graphics that cause you to squint to try to see what's there because the problem is that if the graphics in the book are too low a resolution foe the screen, then the graphics become hard to see. Maps are a very good example of this.

[salamanderjuice]

Originally Posted by JSWolf

What I don't get is when some say that they cannot read from an LCD screen because it bothers their eyes and yet on an eInk screen with a front light, they keep the light way too bright. So how is that overly bright front light not bothering their eyes? I think it could be psychosomatic because they think LCD is not good so they say it's not good yet eInk with too bright a light is not good.

Because a front light by it's very nature works differently from a back light? A back light is basically shining light straight at you. A front light is shining light across the screen like a lamp behind you. One has the source of the light shining directly into your eyes, the other is reflected light. It's not quite the same. You're probably OKAY to look at stuff lit by a 100W light bulb in a small room, looking at even a 40W light bulb directly is a different story. Also since the eInk screen can reflect ambient light as well it doesn't need to be cranked as high to appear as bright as an LCD in the same room.

[HarryT]

Originally Posted by salamanderjuice

Because a front light by it's very nature works differently from a back light? A back light is basically shining light straight at you. A front light is shining light across the screen like a lamp behind you. One has the source of the light shining directly into your eyes, the other is reflected light. It's not quite the same. You're probably OKAY to look at stuff lit by a 100W light bulb in a small room, looking at even a 40W light bulb directly is a different story. Also since the eInk screen can reflect ambient light as well it doesn't need to be cranked as high to appear as bright as an LCD in the same room.

It's really not different. You're talking about light intensity and yes, looking at a 40W bulb can be uncomfortable because it's essentially a point source of light. Spread that same amount of light out over a larger area, and it's no longer uncomfortable to look at, because the light intensity per unit area is lower.

There's no reason to have an LCD screen emitting more light than the frontlight of an eInk reader does, and if both are set to emit the same amount of light, they will be equally comfortable to use.

As I said at the start of this thread, the problem is that many people have LCD backlights set far too high.

[Cinisajoy]

Originally Posted by HarryT

Your eyes certainly don't "know" if a photon hitting your optic nerve has been emitted by, or reflected from, a screen.

All they know is a photon hit them.

[DiapDealer]

But again ...lumen for lumen, your eye does not know the difference between photons that were reflected vs photons that weren't. Which only further strengthens the intensity argument. It's not what happens to the photons before they get to your eyes. It's the intensity of the light when it DOES get there.

Light shined into someone's eyes at the same intensity as light that is being reflected into someone's eyes should generate the same level of eyestrain in an individual (ignoring pixel density of the screen technology for the moment).

Hence most claims of eyestrain from backlit screens HAVE to be because of intensity differences. Whether that is because people don't dim their LCD screens enough when reading, or LCD screens cannot be dimmed enough is a different story.

All I can say is that the brightness on my tablet (which is only ever utilized indoors), is nearly all the way off at all times. I use it exclusively for reading (be it books, websites, email or social media).

I have no trouble believing that many phones/tablets don't provide a way to dim the screen enough for comfortable extended reading periods. But I just don't buy the inherent superiority of reflected vs direct light with regard to eyestrain. At the same intensities, there can be no difference. Therefore: finding the right intensity (given equal pixel-density) is the whole of the issue.

[salamanderjuice]

Originally Posted by HarryT

It's really not different. You're talking about light intensity and yes, looking at a 40W bulb can be uncomfortable because it's essentially a point source of light. Spread that same amount of light out over a larger area, and it's no longer uncomfortable to look at, because the light intensity per unit area is lower.

There's no reason to have an LCD screen emitting more light than the frontlight of an eInk reader does, and if both are set to emit the same amount of light, they will be equally comfortable to use.

As I said at the start of this thread, the problem is that many people have LCD backlights set far too high.

An LCD isn't spreading light out though. It's literally got a layer of tiny-ass lights behind it. That's how it works. On older models it was basically a CCFL light box instead of LEDs. There's no "spread". It's still all a single point of light. Some models don't even dim, they just refresh less frequently and it appears less dim. It's always the same intensity of light for those, just strobing faster than the eye can see.

A backlit LCD always has to be emitting light to be seen. Even to achieve the same visible brightness as a frontlit eReader it has to be putting out more light because it has to compete with the ambient brightness in the room. A frontlit eReader can use the ambient light to appear brighter as it's reflective.

Unless you are reading in a completely dark room, an LCD is going to be putting out more light directly even if it appears just as bright.

[Cinisajoy]

Originally Posted by JSWolf

What I don't get is when some say that they cannot read from an LCD screen because it bothers their eyes and yet on an eInk screen with a front light, they keep the light way too bright. So how is that overly bright front light not bothering their eyes? I think it could be psychosomatic because they think LCD is not good so they say it's not good yet eInk with too bright a light is not good.

I have heard many people say the light on their ereader is too bright and uncomfortable. Upon farther questioning, they have the setting way too high.
This is usually caused by one of two things.
1. Trying to prove a point about the lighting
2. They haven't learned how e-ink lighting works.

Now while typing this I have my tablet on my leg, at a slight angle away from my face.

[4691mls]

Maybe the app used for reading makes a difference too. I read mostly library books, and the Overdrive app has minimal color and brightness adjustments. The Sepia background is a pretty light color. It's better than the white background option, but I would like it a little darker. Also, there's no contrast adjustment. Maybe apps that people are using for purchased books have more options?

[AnemicOak]

Originally Posted by 4691mls

Maybe the app used for reading makes a difference too. I read mostly library books, and the Overdrive app has minimal color and brightness adjustments. The Sepia background is a pretty light color. It's better than the white background option, but I would like it a little darker. Also, there's no contrast adjustment. Maybe apps that people are using for purchased books have more options?

I know for me I've used some weird color combos like a dark grey with light blue, orange or lime green text. Other times it's an image file of old parchment as the background with brown text, etc., just depends.

[graycyn]

Originally Posted by Alohamora

Nearsighted here. I read very happily on a 5 inch LCD phone screen in smallish font with my glasses off. I do keep the brightness low and low room light on.
Not all the devices I use will even go dim enough for reading at night.

I do need the screen resolution to be about 300 ppi or better to be happy with reading on LCD.

Also near-sighted, couldn't read at all on some of the first low resolution tablets that came out, could see pixels, and letters all had a yellow halo around them! Instant headache! But things got better when the 300ppi Nexus 7 came out.

I usually read with my glasses off as well, but that is changing as I get older and my near sight is going south rapidly. I'm happiest with larger screens and somewhat larger font these days.

Sent from my Pixel C using Tapatalk

[Alohamora]

Originally Posted by salamanderjuice

An LCD isn't spreading light out though. It's literally got a layer of tiny-ass lights behind it. That's how it works. On older models it was basically a CCFL light box instead of LEDs. There's no "spread". It's still all a single point of light. Some models don't even dim, they just refresh less frequently and it appears less dim. It's always the same intensity of light for those, just strobing faster than the eye can see.

A backlit LCD always has to be emitting light to be seen. Even to achieve the same visible brightness as a frontlit eReader it has to be putting out more light because it has to compete with the ambient brightness in the room. A frontlit eReader can use the ambient light to appear brighter as it's reflective.

Unless you are reading in a completely dark room, an LCD is going to be putting out more light directly even if it appears just as bright.

Light box style CCFL screens are old school. Nearly all LCD screens are actually side lit these days. The LED s are mounted at the edge and the light bounced around with light guides under the LCD layer.

So actually the light from an LCD screen is less direct than from a lighted eink device, since it passes through the LCD layer in addition to bouncing off the light guides.

[MikeB1972]

Originally Posted by Alohamora

I agree with the first half of your post.

But I don't get how light from a screen is any different from reflected light. When I read on LCD I bring the backlight down to the point that the screen appears the same as a nicely lit piece of paper.

Reflected light is the same brightness as the surroundings.

It's not type of light, it's the difference between the background that causes some people problems.

ie. very bright backlit screen outdoors on a summer day, no problem.
very bright backlit screen down a coal mine in a powercut - massive headache.

[HarryT]

Originally Posted by MikeB1972

ie. very bright backlit screen outdoors on a summer day, no problem.
very bright backlit screen down a coal mine in a powercut - massive headache.

But exactly the same is true of a frontlight, of course.

[JSWolf]

Originally Posted by Cinisajoy

I have heard many people say the light on their ereader is too bright and uncomfortable. Upon farther questioning, they have the setting way too high.
This is usually caused by one of two things.
1. Trying to prove a point about the lighting
2. They haven't learned how e-ink lighting works.

Now while typing this I have my tablet on my leg, at a slight angle away from my face.

When I use the light of my H20, I use 4 or 5%. I find the light can go really bright and I don't want eyestrain.

When I read on my iPad or iPhone, I do turn the brightness down.