shutter speed ?

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donaldjledet

Senior Member
Why does it say on some exif shutter speed 10/1250 or 10/600
and then you see some say 1/500 1/60 and so on?
Does it mean 10sec before shuter release?
Thanks
 
BackdoorArts

BackdoorArts

Senior Member
Forum issue, most likely. I'd think you'd just drop the trailing 0, so 10/1250 = 1/125. Same value, just didn't reduce the fraction. See kids, math is important!! :)
 
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Lawrence

Senior Member
They must have spare digits floating around so they are dishing them out.
Not a bad idea as it stimulates thought and discussion while improving our math.
Funny that most people say "math" where as we (me and my mates from school back in Rhodesia) say "maths"
 
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steve231

New member
The exposure time is the actual time the shutter was open, while Shutter Speed Value is the exposure time rounded to the nearest of a set of industry. But many Nikon models record Exposure Time but not Shutter Speed Value.
 
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WayneF

Senior Member
Right, the exposure time tries to be precise for the shutter, but the marked shutter speed we see on the camera is just a more even approximate value for us dumb humans. Doesn't matter so long as the camera does it right.


Math is important. :)

Fundamental rule: We know one stop has to be a half or double increment.

So starting at one second, and going slower, those steps are 1, 2, 4, 8, 16, 32 seconds.

So the marked speed the camera calls 30 seconds is actually 32 seconds (time it yourself).
And this is of course why a 30 second shutter speed cannot work in 31 second intervals (interval timer - try 33 second intervals for 30 second shutter). And explains that while both third stop and half stop modes have values 10, 20, 1/10, 1/20 seconds, the two modes cannot actually be the same. Close enough for humans though.

And going faster, same way, the marked 1/60 second is hopefully 1/64 second.
The camera knows to do it right.

This nomenclature was decided maybe 100 years ago, before digital made 1/64 be a nice round common number. :)

See the chart of these values midpage at Photographic Tables, Aperture f-stop, Shutter Speed, ISO and EV


My Exif (tool) calls 1/60 and 30 seconds to be 1/60 and 30 seconds. But Exif tools vary.
I use ExifTool.exe (adding the Windows GUI interface)
 
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wornish

Senior Member
WayneF said:
So the marked speed the camera calls 30 seconds is actually 32 seconds (time it yourself).
And this is of course why a 30 second shutter speed cannot work in 31 second intervals (interval timer - try 33 second intervals for 30 second shutter). And explains that while both third stop and half stop modes have values 10, 20, 1/10, 1/20 seconds, the two modes cannot actually be the same. Close enough for humans though.

And going faster, same way, the marked 1/60 second is hopefully 1/64 second.
The camera knows to do it right.

This nomenclature was decided maybe 100 years ago, before digital made 1/64 be a nice round common number. :)

See the chart of these values midpage at Photographic Tables, Aperture f-stop, Shutter Speed, ISO and EV


My Exif (tool) calls 1/60 and 30 seconds to be 1/60 and 30 seconds. But Exif tools vary.
I use ExifTool.exe (adding the Windows GUI interface)
Click to expand...


You just explained why I couldnt get 30sec shots to work every 30secs on my interval timer when I was taking some star shots a while ago, its been bugging me ever since.
Obvious when you think about it.

Thanks
 
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