The two sorts of display resolution improvements

February 29, 2012

Recently I read Matt Simmons' Retina display for Apple: Awesome for everyone, which is roughly about how Apple's increasing use of high resolution 'retina' displays will be good for everyone who isn't happy with garden variety 1080p displays. While I like the general sentiment, I want to sound a quiet note of contrariness because I think that more 'retina' displays will not necessarily do what Matt Simmons wants.

You see (and as Matt knows), there are two sorts of resolution in action here: physical screen size and DPI. Apple's products with retina displays demonstrate this beautifully; they are physically small but have a very high DPI (at least by computer standards; they are low but acceptable by print standards). What most sysadmins want is more physical size with an acceptable resolution; this is the 'more terminal windows' solution. Based on current practice we're okay with relatively low resolutions, on the order of 75 to 95 DPI or so.

(Today I think of 24" 1900x1200 widescreen displays as relatively commodity LCDs and where the starting point for decent sysadmin gear should be; 19" LCDs now strike me as kind of small. This is 95 DPI and also large enough that two side by side horizontally are hard to fit on a desk and expose other issues.)

Increasing DPI without increasing size doesn't really let you get any more windows on the screen; instead it gives you better and smoother rendering of text and other things. This can sometimes make it feasible to use smaller text for windows, but there are strong limits for this (unless you like squinting at tiny text, and trust me, you don't really). Higher DPI plain looks better, though, and Apple's 'retina' displays are up into what used to be the realm of basic laser printing.

There are good reasons for Apple and other makers of small devices to push for high DPI displays. The devices generally can't get physically larger screens (they won't fit the ergonomics), and higher DPI makes small text and non-Latin text much more readable (my impression is that ideogram-based writing systems especially benefit from high DPI). But I'm not at all confident that these high DPI small devices will get makers of conventional displays to do anything to pick up their game, since the environments and the constraints are so different. It probably doesn't help that many people buy regular displays based primarily on price.

(One issue with high DPIs in general is that the sheer pixel counts start getting daunting for decent sized physical displays with high DPIs. My 24" widescreen display at 300 DPI would be around 6000 by 3800 pixels. With 24-bit colour the framebuffer alone is 65 megabytes of RAM, which means 3.8 Gbytes a second of read bandwidth simply to output it at 60 Hz.)

Written on 29 February 2012.
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Last modified: Wed Feb 29 01:34:12 2012
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