I just finished watching today’s Texas Longhorns @ Ohio State Buckeyes football game. I noticed that the stadium lights were on even though the game was being played in full sunlight. That must have some expense associated with it. Why would the lights be on even though it was daylight with good weather and no rain in the forecast? Even with the lights on, the contrast between the sunlight and a shady place would still be quite sharp. I assume this must have something to do with how TV cameras work.
Two reasons. The lights help reduce the difference between the difference between the sunny and shady parts of the field, so players can see the ball better. And yes, TV cameras can deal with a lot of light, or not so much light, but they have trouble dealing with both at the same time.
Although not relevant here, back in the day (going back 75 years here), baseball had a rule forbidding turning lights on during a game. So if there was any chance lights would be needed later, they started the game with lights.
I know of several commercial businesses locally (Walgreens, Bakers Square, Wal-Mart, etc.) that have parking lot lights that are constantly on, night or day. These businesses are (or were) open 24 hours.
I was told by an employee of one that the way they were built, there was no way for them to turn these lights off – no light switch, no timer or photocell control, nothing. The only possibility was to throw the circuit breaker in the electrical box. And that is something that shouldn’t be done – breakers are not designed for frequent use as switches, and will wear out. Plus there may be other items (like alarms) on the same circuit.
I doubt that this applies to stadiums, though – they certainly aren’t designed for 24-hour use!
Usually what I’ve seen is them starting the lights early, so that basically as the game starts, the lights start, and there’s no dusk on the field, nor any sort of abrupt “lights on!” situation.
However the UT/Ohio State game was a mid-day game, so I’m betting it had something to do with TV lighting. I wouldn’t think it’s a contrast thing though; on the field, it’s generally pretty well lit, regardless of whether it’s cloudy, sunny, or under the lights at night.
But for TV, I imagine that it would potentially be important to mitigate the impact of a stray cloud floating over the stadium during play, and having the lights on would help a lot with that.
Many (if not most) circuit breakers made in the last several decades are in fact rated for “switch duty” (and will be marked “SWD” on the front or handle). It’s perfectly normal in places like warehouse stores, factories, etc. to use the lighting circuit breakers as the light switches (and not have any separate light switches).