Why do we say "shutter speed"


4 Nov 2018 6:25PM
After running a couple of "be brave - turn off the auto" introduction courses recently, I'm increasingly irritated by having to explain the term shutter speed when the values we use are not speeds at all but times. Speed is distance per unit time. 1/200s is a time not a speed.
Canon at least marks the dial Tv for shutter priority which suggests T for Time, but apart from that we are lumbered with "speed" pretty much everywhere.
What about a campaign to adopt "shutter time" as a more appropriate term ?

Grumpy retired engineer in Nouvelle Aquitaine.

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Jestertheclown 11 8.0k 252 England
4 Nov 2018 6:32PM
Agreed.

I've been using the term "exposure time" in its place for some considerable time.

Trouble is, a lot of people don't know what I mean!
Tianshi_angie 4 2.6k England
4 Nov 2018 6:37PM
But the shutter does travel - therefore it is surely a speed?
Jestertheclown 11 8.0k 252 England
4 Nov 2018 6:45PM

Quote:therefore it is surely a speed?

No.

Speed is formulated as a distance covered in a specified period time; ie. 60 miles per hour.

1/25th. (of a second) is simply a description of a unit of time. For it to relate to a specific speed, you'd need to include the distance covered during that 1/25th. (of a second).

4 Nov 2018 6:49PM

Quote:Agreed.

I've been using the term "exposure time" in its place for some considerable time.

Trouble is, a lot of people don't know what I mean!



Yes, "exposure time" that's even better.
4 Nov 2018 6:49PM
I started off with a Canon A1 SLR which had Tv on the top dial. I had to look up the instruction manual to find out what it meant because everyone was talking about shutter speed. I have used Canon cameras since so i am used to it now but it is confusing.
Jestertheclown 11 8.0k 252 England
4 Nov 2018 6:51PM
Does the "Tv" on Canon cameras actually stand for anything?
4 Nov 2018 6:52PM

Quote:But the shutter does travel - therefore it is surely a speed?


Yes, the shutter does travel and, as you say, it therefore has a speed, a certain number of mm of movement in a certain time. But that's not what we are interested in as photographers, what matters to us is not how fast it moves when opening and subsequently closing, but how long it remains open. The "exposure time".
4 Nov 2018 6:53PM

Quote:Does the "Tv" on Canon cameras actually stand for anything?



Think it’s “Time Value”....?
SlowSong Plus
11 8.4k 30 England
4 Nov 2018 6:54PM
Seems like ET is the way to go. Makes sense to me.
Jestertheclown 11 8.0k 252 England
4 Nov 2018 7:00PM

Quote:Think it’s “Time Value”....?

OK. Thanks.
PRC 5 216 United Kingdom
4 Nov 2018 7:27PM

Quote:Canon at least marks the dial Tv for shutter priority
Pentax also marks it 'Tv'.

Quote:Grumpy retired engineer...
As a grumpy retired physicist I agree with your argument! Grin
Snapper Plus
14 4.4k 3 Scotland
4 Nov 2018 7:42PM
This reminds me of an eccentric physics lecturer we had at college. He said you shouldn't go into a butcher's shop and ask for a pound of mince, because it was actually a pound force of mince you wanted. Hey ho, good luck with changing every photography book that was ever written. Tongue
Fma7 4 1.0k United Kingdom
4 Nov 2018 8:47PM
Just to be even more pedantic, on an SLR the shutter speed is constant, the gap between then two curtains is the "speed"
djh698 15 6.0k 6 United Kingdom
4 Nov 2018 9:48PM
It's like stopping people saying pin number or atm machine or even worse here in Canada trying to convince people that the game is actually football and not soccer. We may know that we are right but also that we are not going to convince everyone


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