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<blockquote data-quote="WayneF" data-source="post: 367698" data-attributes="member: 12496">Sometimes you need a calculator, but that one is suspect.Enter 6.1 and 7.2 and you get this:&nbsp;&nbsp; <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile&nbsp; &nbsp; :)" loading="lazy" data-shortname=":)" /><img src="http://www.scantips.com/g2/calc2.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />Mine at&nbsp; <a href="http://www.scantips.com/lights/fstop.html#calc" target="_blank">Photographic Tables, Aperture f-stop, Shutter Speed, ISO and EV</a>&nbsp; &nbsp; gives this:<img src="http://www.scantips.com/g2/calc1.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />EDIT:&nbsp; Oops!&nbsp; Hasty.&nbsp; &nbsp;&nbsp; I see now, it was adding to a f/stop value, but I was computing difference between two.FWIW, you can use the same calculator to enter two distances for direct flash, and it computes stops difference for the inverse square law.That is at <a href="http://www.scantips.com/lights/flashbasics.html" target="_blank">Four Flash Photography Basics we must know - Inverse Square Law</a>or enter two Flash Guide Numbers, and it computes stops difference&nbsp; (to be meaningful, of course both GN have to be for the same zoom or coverage, or at least the real numbers actually used).It is at <a href="http://www.scantips.com/lights/flashpower.html" target="_blank">Compare Power Rating of Flashes with Guide Numbers</a>Or the f/stops.<a href="http://www.scantips.com/lights/fstop.html" target="_blank">Photographic Tables, Aperture f-stop, Shutter Speed, ISO and EV</a>But it is the same calculator (same formula).</blockquote>

[QUOTE="WayneF, post: 367698, member: 12496"] Sometimes you need a calculator, but that one is suspect. Enter 6.1 and 7.2 and you get this: :) [IMG]http://www.scantips.com/g2/calc2.jpg[/IMG] Mine at [URL="http://www.scantips.com/lights/fstop.html#calc"]Photographic Tables, Aperture f-stop, Shutter Speed, ISO and EV[/URL] gives this: [IMG]http://www.scantips.com/g2/calc1.jpg[/IMG] EDIT: Oops! Hasty. I see now, it was adding to a f/stop value, but I was computing difference between two. FWIW, you can use the same calculator to enter two distances for direct flash, and it computes stops difference for the inverse square law. That is at [URL="http://www.scantips.com/lights/flashbasics.html"]Four Flash Photography Basics we must know - Inverse Square Law[/URL] or enter two Flash Guide Numbers, and it computes stops difference (to be meaningful, of course both GN have to be for the same zoom or coverage, or at least the real numbers actually used). It is at [URL="http://www.scantips.com/lights/flashpower.html"]Compare Power Rating of Flashes with Guide Numbers[/URL] Or the f/stops. [URL="http://www.scantips.com/lights/fstop.html"]Photographic Tables, Aperture f-stop, Shutter Speed, ISO and EV[/URL] But it is the same calculator (same formula). [/QUOTE]

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