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light screens vs dark screens

How best to use a computer at night?

One approach, with a fair bit of cross platform support these days, is to color shift the screen, reducing white balance to eliminate blue light. This way your brain doesn’t get all confused about the time and you can sleep later. That’s great, but a bright yellow light is still a bright light.

I’m looking at the screen and I look away, and there’s nothing to see until my pupils adjust. The screen is obviously too bright, right? But reducing brightness to a comfortable level has the side effect of reducing contrast. The white (yellow) background is now a fairly dim gray into which the black lettering disappears. I want to maintain contrast while reducing the lumens beaming out of the screen.

There’s a rule of thumb that the screen should be about as bright as a piece of paper. Obviously in the dark, it’s pretty difficult to read plain paper. But we have technology. We can do better.

How about reversing black and white? White text on a black background. This works really well, where I can get it to work. Keeping the backlight at a medium level is kind of wasteful, with the black background absorbing it all, but it allows the letters to shine through clearly.

The real test is when I leave my laptop or tablet open in a dark room, does it illuminate the entire ceiling or opposite wall? At brightness levels sufficient to read comfortably, the answer is yes with a white background and no with a black background.

I’m hardly the first to discover this, and of course it’s something I’ve known for a while now. I always do my programming in dark xterms, and I’ve never suffered much eye strain even programming late at night. On the other hand, switching over to a browser to search for an answer results in instant blindness. But can we go all dark all the time?

Some programs are already prepared for dark backgrounds. The Kindle reading app supports a black background. Alas, it has a distracting amount of window trim that’s fairly light. Fortunately, it goes away in full screen mode. It’s a small detail, but it would make a big difference to make the whole UI reflect the color scheme.

I found it’s easier to read text with a serif font when it’s black on white, but this tends to look fuzzy in reverse. So I also switch to a very clean sans serif font for white on black text.

The biggest issue is web pages. Only a few sites have more than one color scheme (thank you Ars and MARC!). I’ve reworked some of my sites to support both color schemes and it helps. There’s some browser extensions that can rewrite CSS to change background, but I’ve found them unreliable. Either lots of flashing, or they fail to fix the text color resulting in black on black, or some other problem. Frustrating. More motivation to finish work on the various scrapers and proxies I have going. In addition to removing all the crap, I can flip the colors. (Dark Reader for Chrome looks promising; I forget now what extensions I tried before, there’s so many. Bah: it turns Ars Technica inside out so now it’s all bright!)

Another sore point is PDFs. Some of the longer reading material I’d like to spend some time with comes in PDF form. It’s theoretically easy for a PDF reader to invert colors, but this seems to be a most uncommon option. (Zathura could be a contender. Or MuPDF by pressing the i key; should have read the manual, doh.)

In the end, I made some software changes and some habit changes. During the day, I keep everything black on white. It’s the easiest to read in brighter conditions. Then at night I switch the software I can to white on black and stop reading all but a few web sites.

Posted 27 Jul 2017 18:54 by tedu Updated: 10 Aug 2017 15:12