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<blockquote data-quote="WayneF" data-source="post: 351600" data-attributes="member: 12496">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.&nbsp; Doesn't matter so long as the camera does it right.Math is important.&nbsp; <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile&nbsp; &nbsp; :)" loading="lazy" data-shortname=":)" />Fundamental rule:&nbsp; We know one stop has to be a half or double increment.So starting at one second, and going slower, those steps are&nbsp; &nbsp; 1, 2, 4, 8, 16, 32 seconds.So the marked speed the camera calls 30 seconds is actually 32 seconds (time it yourself).&nbsp; 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).&nbsp;&nbsp; And explains that while both third stop and half stop modes have values 10, 20, 1/10, 1/20 seconds,&nbsp; 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.&nbsp; <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile&nbsp; &nbsp; :)" loading="lazy" data-shortname=":)" />See the chart of these values midpage&nbsp; at <a href="http://www.scantips.com/lights/fstop.html" target="_blank">Photographic Tables, Aperture f-stop, Shutter Speed, ISO and EV</a>My Exif (tool) calls 1/60 and 30 seconds to be 1/60 and 30 seconds.&nbsp;&nbsp; But Exif tools vary.I use ExifTool.exe (adding the Windows GUI interface)</blockquote>

[QUOTE="WayneF, post: 351600, member: 12496"] 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 [URL="http://www.scantips.com/lights/fstop.html"]Photographic Tables, Aperture f-stop, Shutter Speed, ISO and EV[/URL] 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) [/QUOTE]

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