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Nikon DSLR Cameras
D7000
Understanding Shutter Speed Settings
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<blockquote data-quote="WayneF" data-source="post: 454760" data-attributes="member: 12496"><p>Simply because if we want each stop to be exactly 2x more light than the previous step (the basis of our exposure system), 1,2,4,8,16,32 is the only choice. We call it seconds, so 1.0 second has to be included, and the rest are multiples, each 2x more than the previous. </p><p></p><p>The camera is marked 1,2,4,8,15,30 seconds, but if that were actually used, the step between 8 and 15 is not exactly 2x more light. And 4 to 15 is not exactly 4x. So the camera uses 1,2,4,8,16,32, regardless of the approximated markings. Same with the actuals of 1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, etc. We humans don't really care about the exact value, but we do want 2x steps.</p><p></p><p>These are just nominal rounded markings for human convenience. We wouldn't like working with actual numbers like 1/813 seconds. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> So we think of it as 1/800, we can easily double or half that in our head, and the camera deals with the accuracy.</p><p></p><p>The camera also claims to have third stops and half stops both called 10 and 20 seconds (and 1/10 and 1/20). But of course third and half stops simply cannot be the same value, they are 1/6 stop apart. Third stops are closer, but 1/2 stops actuals are more like 11.3 and 22.6 seconds.</p><p></p><p>You can time the longer 15 and 30 second shutters to see this is true, they will be 16 and 32 seconds.</p><p></p><p>Old mechanical shutters (springs and gears) were difficult to calibrate, and they did not exceed 1/1000 second, and few even tried that. High speeds simply were not accurate, and it really didn't matter what we called them. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> </p><p></p><p>But modern focal plane shutters use a quartz crystal clock to digitally time the start of the second closing curtain after the start of the first opening curtain, and they are quite accurate now. The same motor drives both curtains at the same speed.</p></blockquote><p></p>
[QUOTE="WayneF, post: 454760, member: 12496"] Simply because if we want each stop to be exactly 2x more light than the previous step (the basis of our exposure system), 1,2,4,8,16,32 is the only choice. We call it seconds, so 1.0 second has to be included, and the rest are multiples, each 2x more than the previous. The camera is marked 1,2,4,8,15,30 seconds, but if that were actually used, the step between 8 and 15 is not exactly 2x more light. And 4 to 15 is not exactly 4x. So the camera uses 1,2,4,8,16,32, regardless of the approximated markings. Same with the actuals of 1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, etc. We humans don't really care about the exact value, but we do want 2x steps. These are just nominal rounded markings for human convenience. We wouldn't like working with actual numbers like 1/813 seconds. :) So we think of it as 1/800, we can easily double or half that in our head, and the camera deals with the accuracy. The camera also claims to have third stops and half stops both called 10 and 20 seconds (and 1/10 and 1/20). But of course third and half stops simply cannot be the same value, they are 1/6 stop apart. Third stops are closer, but 1/2 stops actuals are more like 11.3 and 22.6 seconds. You can time the longer 15 and 30 second shutters to see this is true, they will be 16 and 32 seconds. Old mechanical shutters (springs and gears) were difficult to calibrate, and they did not exceed 1/1000 second, and few even tried that. High speeds simply were not accurate, and it really didn't matter what we called them. :) But modern focal plane shutters use a quartz crystal clock to digitally time the start of the second closing curtain after the start of the first opening curtain, and they are quite accurate now. The same motor drives both curtains at the same speed. [/QUOTE]
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D7000
Understanding Shutter Speed Settings
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