Retina Tax: Some Mac display modes slow down Final Cut Pro X exports

Sunday, 09 November 2014

When Macs first got retina displays with the MacBookPro with Retina display, I wasn't interested. I was used to my 17" MacBook Pro with the 1920x1200 screen option. What was the point of getting a 15" screen that would make 1440x900 look better. 1440x900 points is too small for comfortable editing in Final Cut or any modern UI. I also didn't want the GPU wasting resources supporting a retina display better used for faster rendering and exporting.

My 1920x1200 17" MacBook Pro was fine for HD editing. In Final Cut Pro 7 it was possible to have 2 up display of footage at 50% and 100% playout of HD when going full screen. When I added my 27" iMac, I could view 1920x1080 footage on its 2560x1440 at 100% with either the event viewer or inspector open. In practice when editing HD, I don't often need to see the whole frame at 100%.

Last year, when my 17" MacBook Pro was four years old, I couldn't resist the new 15" MacBook Pro with retina display. The downside of the GPU wasting time on retina calculations was outweighed by faster CPU and very fast 1TB SSD (800MB/s). Knowing that the display could also set to 1920 by 1200 made it good enough for editing in Final Cut Pro X.

Ever since the iPhone 4 introduced retina displays, people have been waiting for desktop retina displays from Apple. When the 27" iMac with retina was first rumoured, I wondered what the point would be for editors. Why have a better rendered UI when what we work with is moving video. Even at desktop viewing distances, it is hard to tell the difference between HD and 4K when video is being updated at 24 or more frames per second.

The cost of retina when exporting from Final Cut Pro X

Again I thought that the GPU would be wasting power on the UI instead of working on video. I visited an Apple Store and used my BruceX benchmark to compare movie export times with and without GPU supporting all the pixels on the retina display. BruceX is a small xml file that doesn't use any external media to test the GPU (and the CPU a little) to export a very complex 2 second 5K ProRes 422 QuickTime movie.

I ran the benchmark on a iMac (Retina 5K, 27-inch, Late 2014), 3.5 Ghz Intel Core i5, 8GB, 1TB Fusion drive, R9 M290X 2GB GPU. The average of four tests was 50.1 seconds. I then used SwitchResX to change the display from 2560x1440 HiDPI (Retina Best) to 2560x1440 (non retina). The export time of the 2 second 5K reduced to an average of 43.3 seconds. That's around 14% faster in non-retina mode. 

So my tip for those who have the iMac with Retina 5K display is to switch resolution to a non-retina mode when exporting more complex timelines when you are under a tight deadline.

For more BruceX results visit this fcp.co thread where people have reported values for many Mac configurations - including Hacktoshes and using many different graphics cards. 

Retina tax also applies to MacBook Pros with Retina

I've also tested my MacBook Pro with Retina (15" late-2013, 2.6 Ghz Core i7, 16GB RAM, 1TB SSD, GeForce GT 750M 2GB GPU).

It turns out that retina More Space display mode is slower than others:

Retina More Space (3840x2400 scaled down to 2880x1800 native pixels): 87 seconds

(Best) Retina (2880x1800 native resolution): 80.6 seconds

1400x900 (doubled in scale to 2880x1800): 80.4 seconds

1920x1200 (scaled up to 2880x1800): 79.2 seconds

So, on Retina Macbook Pros with displays set to More Space, if you want to save a little rendering time in Final Cut Pro X, change the resolution to Best (Retina) before exporting.

Compared with other Macs

BruceX-fcpx-benchmark14

More to the iMac 5K than 27" retina

Only when trying out the iMac at the Apple Store did I remember that the display could be set to 'More Space' instead of 'Best (Retina).' That is an advantage over my current 27" iMac. Here's a 4K clip displaying at 50% on a 2560x1440 screen - showing the same amount of UI that a 4K clip displayed at 100% on a retina 5120x2880 display:

4K-on-27

The 'More Space' setting simulates a 3200x1800 point display on an imaginary 6400x3600 display that's even larger than the native pixels. This is similar to the Retina MacBook Pro 15" GPU showing a 1920x1200 point display by drawing to an imaginary 3840x2400 screen and scaling the image down to the native 2880x1800 pixels.

Working with HD/4K on a 6K+ display allows for more Final Cut UI while editing:

5K more

In this case, I set the event filmstrip size to the maximum. Here is a closeup of those clips at native resolution:

5K more detail

A selection from the full 5120x2880 screenshot.

What would 6K non-retina be like?

A silly thing to do with SwitchResX (and other similar tools such as QuickRes - the tool I have on my Retina MacBook Pro), is to set the display to be 6400x3600 non-retina.

choose-res

The 4K image appears the same, but the UI is half the size:

4K-on-6K-native 

The linked image is a 50% version of the source image (the full 6400x3600 image).

The good news is that although the iMac is labelled as 5K, Final Cut Pro X UI works very well on its simulated 6K display.