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A Flipflop on "Eyeability"
Traveling again. And while I did throw some dead trees in a box to take along, I've been doing almost all of my reading on two devices: My Thinkpad X41 Tablet, and my Sony Reader. The idea is primarily to see if the e-ink display in the Sony Reader really is easier on the eyes than a conventional LCD laptop display. What I've discovered surprised me a little, and has contradicted something I've been saying for ten or twelve years now: That displays operating by generated light are harder on the eyes than displays operating by reflected light.
If it's true, it's not as true as I originally thought it was.
I've done a lot of ebook reading on my X41. I read the ebook version of Chris Gerrib's debut SF novel The Mars Run on it, while sitting in the corner of a poorly lit RV. More significantly, I read Colin Wilson's superb The Criminal History of Mankind on it—and that's a big book, I'm guessing close to 250,000 words. In neither case did I notice my eyes getting any grittier any faster than they generally do reading from paper. I bought the Sony Reader more recently and thus have less data, although (as I mentioned a few days ago) I found out early that the gadget is something less than a blinding flash and a deafening report. Still, The Skylark of Space went past the eyeballs on the Reader without any serious trouble assuming I had enough light to read by.
Eye, (sorry) there's the rub. The Sony's e-ink display is truly a lot like regular paper: You can't read it in the dark. Take it under the covers, and you need a flashlight. And having done a lot of holding it up against various types of books and magazines in various qualities of light, I will go further: It takes better light to read from e-ink than it does to read from any sort of printed paper except newsprint.
Ordinarily this isn't an issue. My reading setup at home is near-optimal: A huge cushy leather chair and a 300W mogul-bulb floor lamp with a glass concentrator. On the road, well, things are different. Hotels are notoriously cheap with light, because light = electricity = money. Reading at night at a Best Western in Kearney, Nebraska was painful. However, add more light and the Reader begins to shine, and when you get to in-car daytime reading, it eclipses the X41 completely. The X41 is close to illegible in daylight, and hopeless in direct sun. The Reader actually looks best when the sun is glaring right on it, and the damned thing should be sold in upscale tropical resort gift shops. (Honestly, Sony should consider developing a unit sealed against sand and water for the George Hamilton set.)
So I stand corrected: There may be less here than meets the eye. One of the advantages of a laptop/tablet display is that it presents a relatively constant light level to your eyes. Paper and e-ink depend on incident light, and readability is affected by the angle at which light hits it. E-ink displays are inherently wider-angle than LCDs, but this advantage is counteracted by the need to position an e-ink display optimally with respect to the light, rather than with respect to your eyes. Book people do this without thinking, but I've also found that having read a couple million words on it, I position the X41 optimally with respect to my eyes now as well, just as automatically.
E-ink will get better over time, and at some point it will not only equal high-quality printed paper in terms of contrast, but also in resolution and levels of grayscale and perhaps even color. (Right now, e-ink is hopeless for illustrations.) In the meantime, I'm realizing that the Thinkpad X41 has been an extremely good ebook reader, and it doubles as a laptop, heh.
(Anonymous)
some realities of visual perception
Recently, I have explored the issue of HDTV resolution vs. screen size, and on the way to understanding it, took a side trip into the issue of human visual acuity. Among the things I learned is that many people who should know better are inclined to say things like "visual resolution extends to one arc-second", as though there were no other factors involved.
Our ability to resolve detail depends on many things. First of these is the light level. Whether the illumination is direct, as through an LCD, or reflected, as with paper or E-ink, the light level is a major factor. And just as with a camera, with higher light, the iris is stopped down, and depth of focus becomes much broader.
In the case of an HD screen, I was interested in viewing distance, and found many interesting things. First, most who pontificate on the subject are simply wrong. One widely accepted chart is not only based on the 1/60th of a degree standard, but also is based on faulty trig! Anyway, with an HD screen, the optimal distance is the one where you are just unable to discern pixels, even on black/white edges. In other words, your eye has integrated the image, both in the sense of smoothing, and that of integrating the whole.
One of the things I did in my exploration was to print out a two inch square filled with black and white lines, each line 0.05" wide. I then taped that printout to the wall, and started stepping backward from it. At the point where I saw a gray square, and no lines, I measured the distance, did some trig, and was depressed to find how poor my vision has become, even with correction lenses. Try it, and you will have a better real understanding of your own vision. And try it in normal room lighting, then in bright sunlight, and note the difference.
For HD screens, the point is that the original goal was to allow viewers to sit closer to the screen, and therefore be more immersed in the view, as in a movie theater (of the old, big-screen, variety). Almost every plan I have seen for a home "theater" has, depending on your perspective, either a too-small screen, or a too-great distance to the viewer.
What this means to e-books, and your LCD vs. e-ink experience, you are better able to discern. I have ample evidence now of what it means to the HDTV experience. And by the way, though the optimal distance for HD depends on the display format, as well as the screen size, the difference between 1080p and 720p is such that if you position for 720p, your sense of detail in 1080p is down about 6dB -- negligible in a visual system with a dynamic range of 9 decades!
You may be interested in looking for more info on these:
Lechner distance (but note that the chart on hdguru.com is incorrect)
modulation transfer function
And look here:
http://www.normankoren.com/Tutorials/MTF.h
Bill Meyer