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Old Sep 15, 2005, 3:17 AM   #21
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chanes wrote:
... I am sorry but I don't understand all of the numbers etc. and how they relate to what I need. Maybe with time I will gain half the knowledge that everyone else has displayed in these postings. Can anyone refer me to an online guide that explains it all??!!
f/stops are a bit more confusing because the numbers appear so arbitrary. This is the standard sequence of f/stops from f/1.4 to f/22. Although it doesn't seem intuitive at first, in this sequence the f/1.4 setting lets in the most light while the f/22 setting lets in the least. Also, each of these f/stops has precisely the same halving/doubling relationship as the shutter speed sequence.
On the face of it, going from f/4 to f/5.6 doesn't sound like halving the amount of light. What's more, 5.6 is a larger number and sounds like it ought to be more light, not less. Neither does f/4 to f/2.8 sound like doubling the amount of light. In fact, each of the numbers in this sequence is a halving/doubling of the amount of light from its immediate neighbours, just like the shutter speed settings are. Not only that, but it makes sense, as I shall show below."
- http://www.uscoles.com/fstop.htm

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