Quote:
Originally Posted by kevgermany
Smaller numbers let in more light cos the f stop is the ratio of the aperture size to the lens' focal length and is more correctly stated as f/8 - i.e the aperture is 1/8th of the focal length. This is why faster lenses are fatter than their slower counterparts of the same focal length.
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I'm glad you included this part. It's so important. We often neglect to make this clear. Too often (i read it all over the net) posters will imply (without realizing it) or a beginner will assume that going to a 'higher' number means actually going to a larger size when in fact its not. It indicates a ratio which defines a relatively smaller physical size.
Lots of beginners nowadays pick up their first dslr never having owned a slr and have no idea that this number represents a ratio and fumble along wondering why the result they get seems opposite of what they intended
Some of it is due to getting the wrong idea about what direction to move the dial when they 'want' larger or smaller apertures.
Instead, unless I'm telling someone to use a particular f/stop I never use 'higher' or 'lower' with the word 'numbers'. I'll say goto a larger aperture or smaller aperture. It only takes once or twice that way for them to see the difference but it sinks in nicely.
It seems so easy to say higher or lower numbers but for me it seems to either confuse or lead to more questions that are hard for them to understand at that point. So when the questions come I try to keep it simple by the "each move cuts/or adds the amount of light" idea. Then I tell them to make sure they read and re-read that in the book. Of course I'm talking about 'informal' discussion w/newbies here.
Thanks, I kinda like your explanation.