Aperture Values - In need of a Full Stop Sequence Clarification

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chilli_vision

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Marcus
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Ok, this might sound like a basic question but I am yet to find a good online resource that explains this specific question.

Is there a common industry standard for what is considered the full stop sequence, the half stop sequence and so on?

I fully understand though looking at the many websites and my own camera that we have huge range of f/stops, i.e. f/1.0, f/1.4, f/1.8, f/2.0.......f/8.......f/22 etc. But, is the following consider the standard full stop (or whatever the technical term is) range.

f/1.4, f/2.8, f/5.6, f/11, f/22

and then every value or f/stop in between is a half or quarter stops in relation to the above full stops. I understand that if you go from f/2.0 to f/4.0 you are still going a complete stop, but this, in my mind is in-between the standard Full Stop range and is either standard half or quarter f/stop in the complete range of all of the possible f/stops.

I am sorry if I am being a little thick, I am just starting out and learning what seems very complex hobby.

Thanking you in advance
Matt
 
If the lens were a simple single element, then the aperture size is directly related to the focal length of the lens -so f/2 is an aperture half the size of the focal length. As the amount of light is proportional to the area of the aperture, it is equally proportional to the f-number squared. So the correct series is in half powers of 2
1, 1.4, 2, 2.8, 4, 5.6, 8, 11 (should be 11.2!), 16, etc which halve the area of the aperture and hence the light at each stop.
 
A 'stop' is a doubling or halving of the exposure. The f-number is a ratio of the focal length to the actual diameter of the aperture. To get a halving of light, the diameter of the aperture decreases by a factor of the square root of 2, which is (as near as dammit) 1.4. Don't forget that the formula for the area of a circle is a function of the square of the diameter.

The sequence of f-stops from f/1.0 goes: 1.0, 1.4, 2.0, 2.8, 4.0, 5.6, 8.0 etc.
 
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As above but to remind you most DSLRs adjust in 3rd stops (although I've got mine switched to half stops) so you can just stick the camera in manual / aperture priority and click the wheel 3 times (or twice in my case) to see where you end up :)
 
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