MacOs pixels per inch and the future

Posted in General at 10 am

I wrote this and sent it to Macintouch for one of their reader reports on Mac OS X:

“John Woo wrote: With OS X my eyes are constantly focusing and I notice it at the end of a day. After the end of an 8-hour day without fail my eyes will be sore and I’ll be nursing a headache, despite frequent breaks for eye relief. I work a 6-8 hour day in front of a a pro 21″ CRT at 1024 X 768 resolution. I can’t imagine what life is like for those poor 12.1″ iBook users.

Heh, heh. Those poor 12.1″ iBook users are laughing all the way past the optometrist’s office. We (I) love the screen because we’re running at 1024×768 just like you, but because our screen has such a higher pixel density, we get *much* greater use out of the anti-aliasing because our screens are displaying 106ppi (Pixels per inch).

Whereas your 21″ monitor clearly shows the additional grey pixels required for standard black on white anti-aliased text, with my 12.1″ screen makes them hardly noticeable. In fact, the pixel density of the smaller iBook shows just why certain visual attributes of OS X which people have complained about are really the direction for the future.

Let’s take the following trends into account:

  • Ever-higher pixel densities (more pixels in a smaller space means higher resolution)
  • The decline of CRTs, the growth of LCDs (and other “solid state” displays, OLEDs, etc)

Add the following facts:

  • Icons and GUI windows have been created for 72ppi for 20+ years.
  • Bitmap graphics get smaller on higher density displays.
  • Vector graphics can stay the same visual size on higher density displays.
  • Text can be presented as bitmaps or as vectors.
  • Text measurement of ‘points’ and screen sizes of ‘pixels’ are the same by convention only.
  • Macs measure type at 72 points per inch, or 1.0 points per 1.0 pixels.
  • Windows measures type at 96 points per inch, or 1.3333 points per 1.0 pixels

OS X/Aqua complaint: “Anti-aliased text is blurry. I hate it.”
Anti-aliased text is going to be necessary as we move towards higher pixel densities. In order to display a 10 point typeface on a 72ppi screen you only need to work with 10 rows of pixels. But with higher ppi screen you may end up using 15 or 20 or even 60 pixel rows. These screen will need anti-aliasing to look good.

It maybe difficult to work with anti-aliased text at 72dpi, but come the future, your screen will be 106 or 150 or more ppi. Aqua points towards that future.

OS X/Aqua complaint: “The icons, scroll bars are so big.”
They may be big now, but as higher density displays become the norm, you’ll be happy to see them. Aqua has a mix of vector and bitmap graphics. Those graphics that are made with vectors can remain the same visual size as densities increase. Bitmap graphics will become smaller and the application UIs will need to be rewritten to support these densities.

Each of these issues are transition problems. OS X/Quartz/Aqua is built to support the future in this regard. Too bad it’s built to support only the past when it comes to file metadata.

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