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<blockquote data-quote="WayneF" data-source="post: 380497" data-attributes="member: 12496">OK, FWIW, I will offer another calculator, to show the computed EV Difference in Any Two Exposure Values.<a href="http://www.scantips.com/lights/exposurecalc.html" target="_blank">Calculator to Compare Any Two Exposure Values, aperture f-stop, Shutter Speed, ISO and EV</a>This one is different than other similar...The value lists here provide the actual correct value. It is done&nbsp; this more messy way because the camera markings are just rounded nominal&nbsp; values, for many years, for human convenience. f/11 is actually f/11.31. ISO 640 is actually ISO 635.30 seconds must actually be 32 seconds. 1/60 second must actually be 1/64 second.Several slower shutter half stop values are marked same as third stop values (but obviously different). This of course affects all calculations, which should use the&nbsp; correct values. Most of these calculators just fudge it to round results&nbsp; to third stops. This one is precise. Those nominal markings do not cause error BECAUSE the camera (and&nbsp; this calculator) instead must know to actually do it the correct&nbsp; precise way... which is, third stop values MUST be cube root of 2&nbsp; greater than the previous, so that three third stops will always come&nbsp; out as a 1.00 full stop difference. The rough nominal markings shown to&nbsp; humans do them no harm.&nbsp; See the detailed shutter speed and EV charts.</blockquote>

[QUOTE="WayneF, post: 380497, member: 12496"] OK, FWIW, I will offer another calculator, to show the computed EV Difference in Any Two Exposure Values. [url=http://www.scantips.com/lights/exposurecalc.html]Calculator to Compare Any Two Exposure Values, aperture f-stop, Shutter Speed, ISO and EV[/url] This one is different than other similar... The value lists here provide the actual correct value. It is done this more messy way because the camera markings are just rounded nominal values, for many years, for human convenience. f/11 is actually f/11.31. ISO 640 is actually ISO 635. 30 seconds must actually be 32 seconds. 1/60 second must actually be 1/64 second. Several slower shutter half stop values are marked same as third stop values (but obviously different). This of course affects all calculations, which should use the correct values. Most of these calculators just fudge it to round results to third stops. This one is precise. Those nominal markings do not cause error BECAUSE the camera (and this calculator) instead must know to actually do it the correct precise way... which is, third stop values MUST be cube root of 2 greater than the previous, so that three third stops will always come out as a 1.00 full stop difference. The rough nominal markings shown to humans do them no harm. See the detailed shutter speed and EV charts. [/QUOTE]

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