Q&A: I’d love the definition of a Retina display, but isn’t it slow?

Q I am a heavy user of Finale, and am seriously tempted to buy an iMac with a Retina display. However other Finale users have reported that it runs slowly on large Retina displays. Why is that?

A A well-written app should not suffer any performance penalty when running on a Mac equipped with a Retina display. However, for that to apply, the app should use device-independent graphics, as Apple has been recommending for many years. This also assumes that the app is handling its own graphics through Apple’s standard libraries: if it uses a third-party cross-platform library, for example, that may incur significant penalties.

The default, and by far the most popular, mode for an iMac 27″ Retina 5K display is – as far as apps are concerned – a resolution of 2560 x 1440 pixels, which is actually slightly smaller than that of non-Retina 27″ iMacs, which run at up to 2560 x 1600. The graphics card then interpolates alternate pixels, so that the display looks as if it is operating at 5120 x 2880, almost four time the pixel count of the older display.

However if the app thinks that it should be controlling the display at 5120 x 2880, and does not take advantage of device-independence, it may well slow down perceptibly.

There are two other factors which you should also take into account. Although all the graphics cards offered for 27″ Retina 5K systems will run that display very well, and almost all have 2 GB of memory, if you are going to use any apps which are graphics-intensive, it is a worthwhile investment to opt for the best of those, currently an AMD Radeon R9 M395 (if you are just going to use the integral display) or M395X (to support large external displays). These are not just intended for playing graphics-intensive games or movies.

The other issue is getting a good Fusion Drive – or, if you can afford it, a large SSD instead. This will allow your Mac to run your most-used apps direct from SSD, which will greatly improve their performance.

Although as a user you cannot optimise the performance of any app, you can stack the odds in your favour when you choose your Mac and its options.