Apple's new MacBook is a light, beautiful and capable notebook for general purpose work. However, compared to the other Apple MacBooks, its Retina display does have one quirk that you may notice right out of the box.
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To explain the wrinkle, I need to backtrack a bit and review Retina technology.
Retina Doubling
There are some fairly standard, legacy notebook resolutions. Two popular ones at the 16:10 aspect ratio are:
- 1440 x 900
- 1280 x 800
When you double those resolutions to achieve a Retina display, they become:
- 2880 x 1800
- 2560 x 1600
If you inspect the technical specifications for the 15-inch and 13-inch MacBook Pros, you'll see that the native resolutions are exactly those last two, respectively. That is, if you count the physical pixels across the display, horizontally, you'll find 2880 and 2560 pixels.
On a display with an aspect ratio of 16:10, the x (horizontal) coordinate is 0.8475 of the diagonal measurement. So, for example, the 13.3-inch MacBook Pro is 11.27 inches across, sideways. That's how Apple arrives at (2560/11.27) = 227 pixels per inch (ppi). The math for the 15-inch MacBook Pro works out in a similar fashion: 220 pixels per inch, and the MacBook comes in at 226 ppi.
On a Retina MacBook, if the Cocoa app has been compiled to be Retina aware, it can write to each of those Retina pixels. The Mac's OS and graphics system then write the rendered display 1:1 to the Mac's display at native graphics resolution, which works out nicely.
The upshot is that each rendered pixel has a real, physical pixel on the LCD display at these resolutions on those two Retina MacBook Pros.
Scaled Resolutions
What happens if you pick one of the other resolutions that isn't the same as the native resolution of the display? It turns out that the OS writes the display at the selected 1x resolution, say 1680 x 1050, renders the page at 2x (Retina) and then scales the display buffer to the native screen resolution. Anand Shimpi first explained this in: “MacBook Pro Retina Display Analysis,” back in 2012.
I asked James Thomson, a noted software developer (PCalc, Drag Thing) about that, and he confirmed it all in an email to me.
When you have the resolution set to something like 1440×900, modern applications that are written to be retina-aware see 2880×1800, and can draw into every pixel. Older applications will get their window contents scaled up by the OS, which leads to the fuzzy look. Usually, standard windows frames and controls will draw in high resolution, even in these older apps.
What complicates things is that screen resolution doesn't necessarily match the pixels on the display. [Emphasis added] The retina displays are so high resolution, and the hardware scaling is so fast, that the OS can draw into a different resolution buffer to do the “Larger Text” and “More Space” options, [see below] and you can't really tell the pixels are not one to one. It's exactly the same as the iPhone 6 Plus, which draws at 3x retina, and then it's scaled down to a lower resolution display.
It's exactly as Anand Shimpi said.
Display Options
If you look at System Preferences > Displays on a new MacBook, you'll see two options:
- Default for display
- Scaled
System Preferences > Displays
It turns out that the Default setting for the MacBook display is not the same as the native resolution of 2304 x 1440. The default turns out to be 2560 x 1600. Why? I surmise that Apple had to weigh the available LCD display technology, in pixels per inch, against what looks good on the screen, provides plenty of working room and yet is easy to read. It turns out that 2560 x 1600 is a better default, and I concur. As Mr. Thomson described above, that 2560 x 1600 rendering is then scaled (very fast) to the native LCD resolution of 2304 x 1440.
Looking at the Displays Preference again, you'll see some scaled options for the MacBook. We've already discussed the Default. The unmarked option (with the red ellipse) is the native option (2304 x 1440). The one on the far left, “Larger Text,” (2048 x 1280) is easier to read. The one on the far right is “More Space” (2880 x 1800), and gives you more room on the display for windows, provided your eyesight is up to it.
But wait! Why, when you float the cursor over the icons, does the caption under the MacBook image in the Displays Preference show exactly half of those Retina resolutions? That's because when Apple went to Retina resolutions, it didn't increase the size of the display by twice. Instead, Apple kept the display the same size and squeezed in more pixels to increase the quality of the display. That's why the caption under the MacBook image has “1x” resolutions and is labelled “Looks like.” That's how a non-Retina MacBook would look at the 1x resolution—just fuzzier.
To make it all a bit clearer, here's a screen shot of a 15-inch Retina MacBook Pro's Display Preferences showing that the Default resolution (Retina of 2880 x 1800) is exactly the same as its physical, native resolution (according to Apple's tech specs).
As a further wrinkle (and clarification), in the AnandTech review of the MacBook, the author Ryan Smith notes:
Moving on, as a Retina display Apple offers a range of scaled (virtual) resolutions, with the MacBook’s default resolution serving as a HiDPI version of 1280 x 800. The fact that the scaled resolution is not exactly one-quarter [emphasis added] of the display’s physical resolution is an unusual first [emphasis added] for an Apple device, but considering the size of the display and power requirements, not to mention the similar PPIs to the rMBPs, I suspect 1280 x 800 scaled on a 2304 x 1440 display was a tradeoff.
Summary
Default resolution settings on the Retina MacBook Pro family match the native resolution. However, at other popular scaled resolutions, the system renders the display at the full Retina resolution and then scales to the user selected resolution on the display. It's virtually impossible for the eye to see the effects of the scaling. For the new MacBook, unlike its larger Retina siblings, the “Default” resolution of 2560 x 1600 is not the same as the native resolution of 2304 x 1440.