Slashdot Mirror

TVs are designed to make video pop. They have a whole host of bells and whistles to help them move out of the showroom. A monitor on the other hand should faithfully reproduce the input it is given.

With a TV there's no guarantees. I've tried and failed to setup TVs for people because dynamic contrast control, or over scan couldn't be turned off, because colour corrections were meaningless, because manufacturers favour over saturated over sharpened colours without enough latitude in the settings to actually turn the features back to neutral.

Do yourself a favour and run through these tests. If they all pass for you already then pat yourself on the back and count yourself really lucky. But more importantly also remember these tests when you next buy a monitor and make use of the 30 day satisfaction guarantee if you have it, because staring at a badly setup panel all day is really draining.

You mean did they test it on improperly calibrated monitors with blown out whites? Go to this site, and reduce your lcd contrast controls until you can see the various grays, because it looks like one would expect even on my adobeRGB wide gamut calibrated display and with Firefox color management mode turned on.

Now, how does it look on a braille reader or links?

I've been using CRT monitors since 1993. I can stare at them all day long as the refresh rate is 75 Hz or higher. At 60 Hz, my eyes get tired out pretty quickly.

As for LCD monitors, I bought one years ago for home use and had to sell it off on Ebay months later when I realized it was giving me eye strain (the effect is noticeable after a few minutes... strain at the temples). For the next 7 years, I avoided LCD monitors when possible, eventually becoming the last person in a 100+ person office to use still CRTs (since I didn't want to give them up at work or home). Even kept using CRT TVs. My theory at the time was fluorescent back lighting was the culprit, since fluorescent lights gave me similar eye strain. To my horror, I got a LED backlit LCD monitor at work and still got the same headaches/eyestrain.

Then one day I realized I was looking at my cell phone screen all the time with zero eyestrain (HTC Incredible, original version as when first released). I was puzzled, until I read that this particular model uses AMOLED display, which is different than normal TFT displays, since the pixels themselves provide the brightness.

Next, I searched to find a test which could stimulate my eye strain pretty quickly. Behold, the test: http://www.lagom.nl/lcd-test/inversion.php
This test creates eye straining flicker for me on regular LCD displays, but not on CRT and AMOLED displays. Hooray. Given this test, I've found some LCD laptop displays to be more bearable than others. For example, Apple Macbook Air (circa 2012) does pretty well on most of the Inversion Walk tests, but not all. My Dell Latitude E6430 (2013) does even better. So good, that I can use that laptop most of the day with its built in LCD screen. Hopefully I'll eventually find a LCD desktop monitor that does well with the Inversion Walk tests. In the meantime, I dream of color e-ink with fast response times, or an affordable AMOLED monitor.

On a side note: older compact fluorescent bulbs gave me similar eye strain. Seems the newest generation of bulbs are bearable, so hopefully I don't have to hoard 60 W incandescents if/when they are banned.

oookay, science done. Result: Apple fails! :P Sub-pixel kerning continues, but does not adjust for the new pixel orientation.

And I'd still like to hear from someone with deeper Windows OS experience that can comment on sub-pixel kerning support.

I haven't tested on the newest variants, but at least by default XP also fails. (thus the question about do those exist ^.^) I do wonder if with Windows 7 or 8 you could get clear type working by going to Adjust ClearType text and selecting the specific monitor in Pivot. I doubt that it helps, as the problem isn't really RGB vs BGR (which I believe it does handle), but vertical vs horizontal subpixel layout, and at least based on http://www.lagom.nl/lcd-test/subpixel.php at least Vista did not support those. It does mention Gnome, but at least on my Ubuntu 12.04 this option seems to have disappeared...

Sounds great. Filtered scaling applied to resolutions that evenly divide native is absolutely fucking obnoxious. In fact, on my lenovo l220x, it looks like it even does it for 1:1! WTF?! (If you are curious about your own display, check out this sharpness test; LCD sharpness at native resolution should be perfect. If it is, using 50% pixel patterns vs. 50% colors allows calibration of a display by eye. If not, software that takes advantage of this principle totally fails.)

We also have an (expensive) 120Hz Sony Bravia HDTV that also can't even do 1:1 properly. Part of the problem is that without DRM support for HDMI, the 1920x1080 is crippled and scaled down. To add insult to injury though, it can't even scale properly, and insists on cropping a significant part of every screen edge, making it worthless to display output from a computer. (The menu bar and dock on a mac are off screen.) The scaling options available aren't even suitable for TV purposes.

The first shimmering phenomenon is just analog interference. I'm not quite sure about the second, though I have observed it. Interference with the polarity inversion is one possibility, considering the flickering occurs at about 30 Hz on my displays. I don't see tearing, but I have vsync turned on in compiz.

Here:

http://www.lagom.nl/lcd-test/

http://www.lagom.nl/lcd-test/

Then there's the issue of viewing angles -- most LCDs have a wide horizontal viewing range, but a narrow vertical viewing angle range. Rotating the monitor flips that. (It's not as big of a deal as you'd think, in that I sit in generally the same place, but it makes it harder to read stuff there if someone is sitting next to me.)

I think you nailed a big part of the problem, and don't even realize it.

Sure, your head might generally be in the same place, but the viewing angles on common TN panels can be so horrible that each eye sees something very different when rotated.

I used to have a cheap Motorola flip phone which had this problem: Things looked all crazy just holding the phone in my hand in its default portrait mode, but fit together just fine with it rotated sideways; clearly, they'd simply bought whatever LCD screens were available without any regard as to their intended orientation. (Amusingly, the phone was useless in sideways orientation...)

I have a rotatable 20" 1600x1200 IPS display which does work fine (and aces the below test) when rotated vertical, but I had Cleartype turned off the last time I tried that. (I'd be willing to see how it behaves with Cleartype enabled under Windows 7, if you ask.)

The 24" 1920x1080 TN display that sits on the desk beside it, though, is extremely bothersome to view when rotated 90 degrees.

To demonstrate what I'm talking about, I direct you to these LCD monitor test images, specifically this set. Give it a spin on both screens, and give your head a 90 degree twist to see the differences.

Then there's the issue of viewing angles -- most LCDs have a wide horizontal viewing range, but a narrow vertical viewing angle range. Rotating the monitor flips that. (It's not as big of a deal as you'd think, in that I sit in generally the same place, but it makes it harder to read stuff there if someone is sitting next to me.)

I think you nailed a big part of the problem, and don't even realize it.

Sure, your head might generally be in the same place, but the viewing angles on common TN panels can be so horrible that each eye sees something very different when rotated.

I used to have a cheap Motorola flip phone which had this problem: Things looked all crazy just holding the phone in my hand in its default portrait mode, but fit together just fine with it rotated sideways; clearly, they'd simply bought whatever LCD screens were available without any regard as to their intended orientation. (Amusingly, the phone was useless in sideways orientation...)

I have a rotatable 20" 1600x1200 IPS display which does work fine (and aces the below test) when rotated vertical, but I had Cleartype turned off the last time I tried that. (I'd be willing to see how it behaves with Cleartype enabled under Windows 7, if you ask.)

The 24" 1920x1080 TN display that sits on the desk beside it, though, is extremely bothersome to view when rotated 90 degrees.

To demonstrate what I'm talking about, I direct you to these LCD monitor test images, specifically this set. Give it a spin on both screens, and give your head a 90 degree twist to see the differences.

[sarcasm]
Of course, it's plain to anyone that all of the problems you experience with color purity on your HP ZR24w are completely and totally caused by the fact that the outer-most surface of the screen is not shiny. Everyone knows that matte displays have always had these problems.
[/sarcasm]

Which is strange because, you know, I'm writing this in front of an non-glossy 24" Asus VW246, and it exhibits very consistent colors and whites across its entire display area. It's got a whole slew of issues that I'm not happy about (many of which are properly exposed in these LCD monitor test images), but color purity and blotchy white aren't among them at all.

So while you might conclude that matte displays cause color issues, I must only conclude that you got ripped off.

It happens to everyone from time to time. Send it back if you still can.

We're not talking about distinguishing pixels in arbitrary display images, least of all anti-aliased fonts (whose very point is to conceal pixelation).

We're talking about optical resolution here, so load some 1px pitch black/white patterns (e.g. http://www.lagom.nl/lcd-test/sharpness.php) and see at what distance you see gray instead of lines/checks/whatever.

Fix your monitor, and you'll see it just fine.

If you're looking for lcd test images, http://www.lagom.nl/lcd-test/ is probably better. It's got a whole bunch of images dedicated to various monitor problems, along with explanations.

Just because LCD monitors don't refresh like a CRT does, doesn't make them perfect.

I had a Viewsonic VG930M 19" LCD, which was an absolutely lousy monitor. Certain colors and shades would be very obviously and visibly noisy, due to the dithering used to approximate colors which the display was incapable of producing. (This is mentioned in your linked Wikipedia article on LCDs, down under the Drawbacks heading.)

For a demonstration of this and some other problems with these displays, head over to this handy LCD test page. All of the images there are static, but depending on the display, some of them will flicker and do weird things to such an extent that you'll swear it's an oddly-smooth animated GIF concocted to con you into thinking your display is shit.

My fast, newish Asus TN-panel display does OK on most of that page. My somewhat slower, and far prettier (and more expensive!) IPS-panel NEC does a better job on some, but not all of it. Meanwhile, some of the stuff there hurt to look at with the aforementioned Viewsonic. (For reference, all monitors connected with DVI, all attached to the same video card, on the same PC, and driven at their native resolution.)

In conclusion, let me just say that under not-so-uncommon circumstances, perfectly normal LCD displays can and will flicker. Indeed, it's not a refresh rate issue. But just because folks sometimes use the wrong verbiage to describe a problem doesn't mean that they're not experiencing one at all, nor does it always indicate that they're suffering from audiophile-itis.

FYI, there is a relatively reliable and uniform way of measuring your LCD contrast ratio http://www.lagom.nl/lcd-test/contrast_ratio.php

OK, so go to System->Preferences->Appearance, click Fonts, then Details. Make sure you have subpixel turned on with hinting set to full. Also make sure the subpixel order is right. You can check that using one of the LCD test websites, like this one. It definitely looks just as good as XP with Cleartext for me.

You never want to defrag SSD's. It just wears out the disk. A good SSD has wear-leveling and write-combining techniques that keep the SSD "defragmented" automatically.

I recently did an experiment on the impact of fragmentation on a flash drive, and it does seem that there are significant issues with fragmentation, although I'll be the first to acknowledge that I only tested one device so far and that an older SD card is not a modern SSD.

It looks like writing flash memory is very slow (tens of milliseconds for a write), which is compensated for by parallelizing writes in large (100+ kB) contiguous blocks, with obvious consequences for performance on writing scattered data. It would not surprise me if high-end SSDs parallellize their write operations across the separate physical chips inside so that a single write does not block all other read/write access to the device, but wear and access would still be better if data is stored contiguously as much as possible.

In terms of eye strain, what does the panel technology matter? Even the cheapest TN panels are perfectly sharp when you use a DVI connection.

I would recommend going to this page and check out some of the test images:
http://www.lagom.nl/lcd-test/

Obviously if your primary concern is eye strain, you may not care much about the color rendering and whatnot, but a monitor where the contrast is good and has minimal pixel-walk and other artifacts would be best.

I believe you are wrong and you will need to provide me with some links. Most LCD panels used for consumer LCD monitors are indeed only 6 bits per color, and are dithered in the time domain to get some sort of semblance of more colors. Why do you think one of the numbers used to sell LCDs is the response time? Who cares about a response time of 6 or 4 ms on a panel that displays only 60 pictures per second, ie every 17 ms? It's because that's what allows the dithering to happen. I happen to own one of the first and one of the few true 24 bpp LCD monitors, the SGI 1600. Of course now I can't find the one web page that showed you how to find out which kind of panel you have, but it used to be at http://www.lagom.nl/lcd-test/. It is no longer there. Anyways, those 300$ 24 inch LCDs? 6 bits per color, guaranteed.

Get your digital camera

I have a website where you can upload your screen images and have it calculate with higher accuracy what the contrast ratio is: lagom.nl/lcd-test/contrast_ratio. I tried this myself with dozens of screens (in a dark environment), and nearly all recent laptop screens have a contrast ratio of around 1:100 - 1:150 in a dark environment, a bit dependent on the viewing angle. Glossy or matte doesn't matter. I didn't check the effect of ambient light on the contrast ratio.

This value doesn't even give you the full dynamic range from an 8-bit display (255 to 1),

It doesn't work like that; the standard sRGB brightness-versus-pixel value response curve of a standard computer monitor means that officially, the brightness ratio between 1 and 255 "should" be more like 3000:1.

let alone the 1000+++ to 1 that LCD TV manufacturers claim.

I don't have much experience with LCD TVs, but if they are based on the same LCD panels as monitors (likely the case up to 24 inch), you won't get much better than about 800:1, unless the TV dims the backlight during dark scenes.

2. Open your favorite image editor. 3. Create a diagonal gradient starting with black and ending with 50% pure blue or green

(Shameless plug) Rather than creating the image yourself, you can also try The Lagom LCD test pages (and try lots of other monitor tests as well).

we use images taken from a little-known anime. You are to input the name of that anime in order to get acceptance for registration. We haven't had any spam since we implemented this a few years ago.

Well, I have a guestbook-like webpage that got spammed pretty badly, and I added the question:

What kind of being are you? [x]robot [ ]human [ ]frog.

It blocks all the spam. That's because there are plenty of bots that just look for anything that looks like a text submit form and they're not going to spend even 5 minutes on cracking it. But no way that it would work if it was in the standard distribution of phpBB.

(The silly captcha is here. I also have a much more robust captcha which I'm sure is quite hard to beat.)

we use images taken from a little-known anime. You are to input the name of that anime in order to get acceptance for registration. We haven't had any spam since we implemented this a few years ago.

Well, I have a guestbook-like webpage that got spammed pretty badly, and I added the question:

What kind of being are you? [x]robot [ ]human [ ]frog.

It blocks all the spam. That's because there are plenty of bots that just look for anything that looks like a text submit form and they're not going to spend even 5 minutes on cracking it. But no way that it would work if it was in the standard distribution of phpBB.

(The silly captcha is here. I also have a much more robust captcha which I'm sure is quite hard to beat.)

It would be nice for airport displays. A single server can drive all displays and no restrictions on video cable lengths. Apparently, it currently is one server, one video card per display. But maybe I'm mistaken.

If it is a 6 bit panel, then you can use dithering with four pixels to achieve 253 different values in each color component (that is 253, not 256)

I have heard this many times, but last time I bought an LCD screen, about half a year ago, I brought a couple of home-brewn test images to the computer store and basically all of them (price range up to EUR 350) seem to do time-domain dithering, which is especially visible in the darker areas. Also, the better screens in this price range (I ended up picking a Samsung 203B, 1400x1050) can display all shades from 0 to 255 without chopping off the lower or higher three.

Physically, this makes sense. The luminosity is supposed to be a nonlinear function of the pixel value (L = n^2.2), and the luminosity of a pixel is some other nonlinear function of the applied voltage, so in order to come anywhere close to the desired gamma of 2.2, the hardware in the monitor has to do more complex dithering than in 4-pixel blocks.

So can anybody provide a reliable reference for this 253-shade claim? I mean, from somebody who actually knows how the hardware is wired?

Quiet acquiescence solves nothing. If a website screws up its fonts, complain. I'm a web developer, and I'd hate to think people were silently putting up with mistakes I made instead of telling me about it.

I actually have a website with a small community that had been running with 100% fonts for quite some time. It turned out that several people didn't like my layout and used one of the forum-software-supplied default style because my fonts were too big and setting the browser defaults +smaller makes the rest of the web too small. When I changed the fonts to 82% (14px) I surely got a complaint that it was too small. I ended up giving users the option to switch font size.

At the same time, I set my browser defaut to 14 px rather than 12 px. It really saved me a lot of headache since most websites render in a much more consistant manner without me having to hit the zoom key all the time.

screens are a lot bigger these days. I don't need to cram everything down to the smallest size possible. So I started using the default settings. And you know what? I could read stuff a lot smaller, but it's a lot faster and easier on the eyes to have it at a sensible size. And despite what you think, that doesn't mean I am visually handicapped.

Actually I think you are above 45 years old and are postponing the purchase of reading glasses and instead increasing the distance between your eyes and your screen beyond normal reading distance. :-) Screens are indeed bigger nowadays, but most consumer-grade big 19- or 20-inch screens are still 1280x1024 pixels, just like the 17-inch screens have been for quite a few years, so increasing font size does cost you screen real estate.