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Making an Inch an Inch June 3, 2009

Posted by gordonwatts in computers.

In one of my last posts I wrote about Bill Hill and his efforts to improve onscreen reading. For me this has always been about high resolution displays. It would seem that Bill, who has thought about this a lot more, agrees. When I buy a portable there are two criteria. First, it has to be a convertible tablet. Second it has to be high resolution. The high resolution is for one reason only: gorgeous rendering of PDF documents. The more pixels per letter the better the letter looks. It definitely works!

Bill is constantly raving about his brand new Apple (he is running Windows on it):

But I have to say, their displays were not in the same class as this 133ppi display from Apple. It’s stunningly bright and crisp.

The key here is crisp. I have a large 1280×1024 monitor at home. It has one of those glass screens – the ones that reflect and are really really bright. I’ve never seen my photographs look so good as on that screen. But pop-up a PDF and compare it to my 1080p 24” screen? No comparison. Looks a lot better.

There is one problem. The OS and web pages. They all render things much smaller than they are designed to.

In Bill’s blog postings, however, I discovered there was a way to configure Windows to set the DPI correctly. Basically, if you asked your computer to draw a line an inch long on your screen, it would come out an inch only if your screen was built at 96 DPI. My X61T is 147 DPI! That makes the text too small. So my 9 pt text appears as something much smaller, which can be a problem:

It’s especially complicated because humans need (not want, need) to read type which is between 9 and 13 points high. This dimension is dictated by the size of the foveal area in the retina of the human eye, which is only 0.2mm in diameter, with about 1.5 degrees of visual arc.

Ok. So at least Windows has something in it that will allow it to set the Pixel DPI. I set it to 147. Boom. The inch was really an inch (I’d never seen that before). But it was also clear that not much else would work! Web pages were a disaster. Many programs I depend on acted very oddly (who would have thought RealVNC would have so much trouble with a setting like this!?). Such a pity, but MS Office, and the OS itself looked pretty good. So I had to set everything back (to about 120 DPI). My impression from reading around is because most programming is done in terms of pixels, not in terms of actual sizes or lengths. I’d never given this any real thought when writing my own code.

BTW, I have a Lenovo X61T for my portable. The high resolution screen is great (hey, better than the Apple), but it isn’t as bright or crisp as I’d like it. Apparently that is because it is a tablet, so the digitizer takes the edge off it a bit. So it is a compromise machine in that sense.



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