Why tennis balls are yellow or green | Hacker News Reader

Why tennis balls are yellow or green

artsy.net

115 pointsTomte50 comments

Tennis balls are fluorescent; UV light gets reflected back as a set wavelength. This means they'll be brighter than a non-fluorescent yellow/green and thus easier to see. The amount of UV light (time of day, natural vs artificial light, overall light levels) will push the subjective colour between green and yellow.

This becomes a minor consideration when doing tennis court lighting upgrades, as Metal Halide lamps emit UV whilst new LED ones don't. Since tracking of the ball is primarily based on strong and consistent contrast against the background, having a UV light component that only lights the tennis ball is a major boon.

Tennis can be played under blacklight with relatively weak lights: https://www.youtube.com/watch?v=-x4mfQITXtM

Being fluoreszent makes a lot of sense, as it vastly increases the brightness of the balls. Hadn't thought about them being fluoreszent. But for the fluoreszent effect, it is sufficient that the light has a shorter wavelength than the floreszent color. So any wavelength from normal green into the blue spectrum should work, no need for UV for that.

> for the fluoreszent effect, it is sufficient that the light has a shorter wavelength than the floreszent color. So any wavelength from normal green into the blue spectrum should work, no need for UV for that

That is not how fluorescence works. You have a fluorescence excitation spectrum offset from the emission spectrum and there is a peak. I don’t have the spectrum for a tennis ball, but it very well could require UV light for any meaningful fluorescence

https://www.sciencedirect.com/topics/chemistry/fluorescence-...

Yes, of course, there is some offset between the absorption range and the emission wavelengths. But there is no requirement for the absorption to be in the UV region. The absorption range is also wide peak. All the fluoreszent colors which "work" with e.g. car headlights have a sufficiently strong effect in the visual range. It is also an easy test for fluorescence to shine e.g. a blue light at something which has a strong orange color. If it still is strong orange, fluorescence obviously is the dominating effect. I don't doubt that UV light shows a strong fluorescent effect, especially as you cannot see the UV light itself, but of course the fluorescent emission it is causing.

Is there much use of fluorescent colors that work in car headlights? For signs and markings, reflective paints seem to be more effective in showing up under headlights, particularly as the light is directed back towards the source, rather than scattered widely.

The article below describes the benefit of fluorescent dyes under weak natural light, as they can use the UV component of natural light to increase the amount of visible light reflected. Downshifting visible light to a longer wavelength, which is what fluorescence excited by visible light would do, would reduce the intensity of the reflected light.

https://www.3m.com/3M/en_US/road-safety-us/resources/road-tr...

This discussion could use some examples, and there seem to be some named dyes here that are excited by visible light. On the other hand, the simple fact that it was an issue in the replacement of tennis-court artificial lighting shows that UV excitation is a factor in the fluorescence of the dye used for tennis balls.

https://www.thermofisher.com/us/en/home/life-science/cell-an...

I wonder how many daily things still have fluorescent elements. In the 90s there was a little fad (my ikea bed light has a fluorescent switch, and we had a few items like this).

LED replacements for Fluorescent tube lights are very common now. took me by surprise because for some reason the idea did not register until I saw them when I needed a replacement.

end of summer they finally replaced the remaining halogen street lamps in my neighborhood, we had an every other arrangement. now I have light the equivalent of a full moon which is both good and bad out front

There are 3 different kinds of LED T8 replacement lamps. ‘Type A’ use the existing fluorescent ballast, ‘Type B’ use an external LED driver, and ‘Type C’ use a driver integral to the lamp.

White shirts and office paper have fluorescent dyes.

This is also how "whiter than white" detergent works.

And why bees will sometimes harass people that look too much like a tasty flower.

> Tennis can be played under blacklight with relatively weak lights: https://www.youtube.com/watch?v=-x4mfQITXtM

1:14 "The balls we use are green dot balls and orange balls"

So they are not using standard yellow balls for UV light games.

They're using low compression (lower speed, kid friendly) balls, often they're the same colour as your standard adult tennis balls just with a small alternatively coloured circle to indicate.

https://www.tennis.com.au/learn/rules-and-scoring/10-and-und...

Look at the box of balls at 1:30.

> 1:14 "The balls we use are green dot balls and orange balls"

> So they are not using standard yellow balls for UV light games.

A "green dot ball" is exactly the same color as a standard ball, except it has a dark green dot stamped on it.

The answer:

> For nearly a century, tennis balls were white or black...In the late 1960s ...the BBC... broadcast Wimbledon, perhaps the most iconic of tennis tournaments, in color for the first time ever.

> Broadcasting tennis in color brought the matches to life, but it made tracking the ball on screen difficult — especially when it fell near the white courtlines. So the International Tennis Federation (ITF) undertook a study that found that yellow tennis balls were easier for home viewers to see on their screens. An official 1972 ITF rule change required that all regulation balls have a uniform surface and be white or yellow in color. However, despite the difficulties for TV viewers, Wimbledon did not change the ball color to yellow until 1986.

Far more interesting than the colour is the weight. A lot of tennis critics these days think the surfaces are becoming more similar - clay is getting faster, grass is getting slower, etc.

What has actually happened is the various federations change the ball based on the speed of the surface. Slow courts get faster moving light balls, and vice versa.

This is actually very well documented the ITF have posted everything from press releases to research papers - but commentators still seem to think that the composition of mud has changed significantly in the last 10 years!

It's the first time I heard this and I'm really surprised. Do you have any link related for those press releases?

A simple Google search doesn't seem to give any good results and ITF's site is not the most user friendly for searching.

https://bleacherreport.com/articles/547256-how-the-humble-te...

I was an average tennis player in high school and later took a class in college.

The only scent as powerful and nostalgic as tennis balls that I can think of is that of a new car. It must be some weird chemicals or adhesives used in the manufacturing process. I sure do love it, though. I’ve actually got a bottle of new car smell concentrate which is half decent that I use instead of candles and typical scents at home. I’d buy a tennis ball scent if they sold that, ha.

> I’d buy a tennis ball scent if they sold that, ha.

Try to get your hands on some camphor ;-)

Isn't that like vicks vaporub? That stuff is a strong scent too... just different.

What about the smell of new electronics?

I’m not sure if I know what you mean, I don’t usually smell new electronics?

Yes, new Apple hardware in particular has a very distinctive, pleasant and hard to describe smell.

The flouro wasn't adopted immediately. When I was on my high school tennis team (79-82) we mostly had white tennis balls except when some kid brought in a tube of the "exotic" ones.

We had wooden rackets (stored in press frames) back then too. The modern game of tennis is practically unrecognizable when compared to that era.

(Get off my lawn! I suppose).

Wimbledon used to use white slazenger balls.

https://images.app.goo.gl/W7Edd15tbHbB8Kkq8

Essentially it's for the exact reason you think: so people could see the ball better.

The interesting part is that it wasn't for the players to see the ball better, but television watchers.

They tried to do it digitally with the hockey puck (FoxTrax glowing puck tech) but it got poor reception.

If they has set the trails to 20 instead of 100, I think it would have bugged less people. As it was, it popped too much and made the game look like a background.

Same happened with billiards: the plain white cue ball got 6 or 8 red dots put on for TV viewers to be able to see the spin a bit. Of course the players can benefit too but that's not why they did it, and many pool halls still use plain white balls when not hosting serious competitions.

Same reason high visibility jackets are I presume. I always think they're green but others tell me they're yellow. I have normal color vision as do at least some of the people who see them differently

Federer says yellow - https://www.youtube.com/watch?v=1at7aQqjhC8

Yes I think I'm in a minority on the issue but I'm not alone!

I always just assumed school buses were yellow because they're always referred to as yellow, but then my 3 year old child said "look at the orange bus" and as I looked, I realized that indeed the colour of a bus appears to be more orange than yellow. Now I can't un-see it.

Can't imagine confusing orange with yellow. Do you know what the general consensus is on the color?

Woah this is weird. I just re-listened to the Hello Internet episode where they were discussing this question.

Ask HN: Am I in The Truman Show?

Baader-Meinhof Phenomenon :)

This gives me an idea for "hard mode" tennis, with camouflage balls...

'Why clickbaity headlines that bait you with the answer to an unasked question are annoying'

The original article on Artsy (which CNN links to) is better illustrated:

https://www.artsy.net/article/artsy-editorial-reason-tennis-...

Changed from https://edition.cnn.com/style/article/artsy-tennis-ball-desi.... Thanks!

TL;DR: they used to be black or white but changed to yellow for colour TV.

Also, there aren't two different colors of balls, yellow and green. There is one official color that some people judge as yellow and some as green.

Say it ain't so!

Being a stickler about color theory, I keep trying to get people to say that tennis balls are chartreuse, but I don't have a lot of luck: https://en.wikipedia.org/wiki/Chartreuse_(color)

To me, calling that color "yellow or green" is like trying to use the words "red or yellow" to describe orange.

They look more like yellow than chartreuse to me. Colour names are all opinion - not much point arguing about it or trying to convince anyone of your opinion.

Snooker was always a fun watch on B&W TV. You kind of figured out the different greys, with a little help from commentary pointing out that the blue was now behind the yellow... err... :)

Surprisingly it worked well enough to be worth watching.

There was a famous 'gaff' by commentator Ted Lowe, who said: "Steve is going for the pink ball - and for those of you who are watching in black and white, the pink is next to the green."

Worth noting that this sounds like a joke or a gaffe, but might have been a very reasonable thing to say. Assuming the green was on or near its spot (its starting position), which is likely, every snooker fan would know which ball was the green.

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