How big should subtitles be?

Thursday March 14th 2:20pm - 3:00pm

Ed White

User Experience Designer, Audio Video Key Experience, BBC edmund.white@bbc.co.uk

Nigel Megitt

Executive Product Manager, Platform Media Services, BBC nigel.megitt@bbc.co.uk

About us

Production	⇨	Media Services	⇨	Player
		Nigel		Ed

Nigel

The Media Services team in the BBC provides the technology for managing media across the BBC, be it storing media, moving it around, transcoding or encoding, packaging, managing availability or playing it back. When the audience watches a BBC video on the web or on their smartphone or tablet, perhaps using the iPlayer product or Britbox here in the US, the player is almost always the BBC’s Standard Media Player, a product owned by Media Services.

Ed

The Audio Video Key Experience team provide UX design for the BBC’s Standard Media Player (SMP). This is an audio and video player that is used on all the major BBC online products including our video streaming service iPlayer, BBC Sounds and BBC News. We consult with these products to understand their requirements, and their audiences, and we also design, test and implement new features for the player.

Hypothesis and research design

Hypothesis

Nigel

We could have just measured the preferred size on a range of different devices, but we were curious to know if there is a rule we could apply more generally, so that if new device types come along we could apply the rule and calculate what size is most likely to be “best” for it.

The hypothesis we wanted to test is if there is a preferred apparent size, measured as an angle. If you look at a smartphone or tablet, you probably hold it quite close, the distance range being determined by how close you can focus and how long your arms are. There may be a bit of variation between a phone and a tablet, but because the tablet is so much bigger a screen, the apparent size of text is likely to be much bigger.

Similarly, we know from research about our audience’s television watching environments (BBC R&D White Paper 287) that the distance of the television from the viewer is rather static, and has been over some decades, because it is determined by the size of the room. However the size of screens has got a lot bigger.

So any text whose size is proportional to the height of the video will apparently have got bigger.

In order to calculate the “angle subtended at the eye” we need three things: the distance from the eye to the screen, the real height of the text, and some basic trigonometry. We knew the screen sizes and distances for televisions from previous research, but not for phones, laptops and tablets. So we wanted to complete that data set and see if the hypothesis is true, that viewers prefer an apparent size of text as measured by angle.


40 Participants	8 Devices
Aged 13 to 83 years old All subtitles users	2 mobile, 2 tablet, 2 monitors, 2 TVs


1 customised SMP	1 Measuring tape
2 Font Variations 9 Size Options	To record the distance of the device from the user.

What the data told us

	Median angle	Median viewing distance/ mm	Median height/mm	Exact multiplier	Closest multiplier match	Participant preferred multiplier
Standard Phone	0.56	340	3.3	1.00	1	1
Large Phone	0.43	410	3.1	0.68	0.67	0.67
Standard Tablet	1.11	430	8.3	0.84	0.825	1 or 0.75
Small Tablet	0.59	405	4.2	0.72	0.75	0.6
Large TV	0.51	2630	23.4	0.67	0.67	0.67
Small TV	0.43	2630	19.9	0.75	0.75	1 or 0.67
Laptop	0.67	605	7.1	0.57	0.6	0.5
Desktop	1.46	450	11.5	0.57	0.6	0.5 or 0.75

1 . 1

How big should subtitles be? Thursday March 14th 2:20pm - 3:00pm Ed White User Experience Designer, Audio Video Key Experience, BBC edmund.white@bbc.co.uk Nigel Megitt Executive Product Manager, Platform Media Services, BBC nigel.megitt@bbc.co.uk These slides: bbc.github.io/csun Nigel Welcome everyone, thank you for coming. In this session we're going to talk about a piece of work we did in the BBC to try to establish how big subtitle, or closed caption, text should be, based on mathematical theory, user research, the art of the possible, and user monitoring. I'm Nigel, and this is Ed. If you want to look at these slides, you can find them and other BBC presentations from CSUN at this URL bbc.github.io/csun and follow the link.