Aperture Size terminology


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sprockett

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Aug 9, 2002
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#1
hi, i see so many put the aperture size in different terms from the f2.8, blah blah etc like on my S45...

f2.8 stands for wat size ah? i know its the biggest but what is the actual size?


i see b4 some pple got put aperture size 15, 10, etc... what is that in the fxxx terminology?

pls advise.. thanks bros!
 

Nerd

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Oct 25, 2002
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#2
F size gets bigger, the actual opening gets smaller. So f2.8 is actually bigger than f3.5

f sizes goes from f1.2 to f22 (should have smaller ones [bigger f] but don't know how far it goes)
 

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#3
Okay I'm gonna give a shot trying to explain what aperture means.


If you studied physic in your secondary school, you might have know how to make a pinhole camera right?

Well, aperture is like the pinhole of the camera. It's where the light penetrate to your camera and make exposure onto your film.
Bigger hole (which means bigger aperture) produce blurer images while small hole produce sharper images. In photography term, we call that Depth of field (DOF).

The numeric represent the size of the hole. The bigger the value of the number (e.g f22) the smaller the pinhole (aperture). In another words, a f2.8 has a larger hole than f22.

What are the hole sizes for?
Well, that's where speed come into play. The bigger the hole, more light will be allowed to penetrate to your film, and thus requires a shorter time of exposure. This will be crucial when you need to freeze moment (e.g people falling out from the window. ) But it will also contribute to a shallower DOF (background blurer).
But again exposure have to depend on the lighting of the situation. Sometime, even with big aperture the time of exposure could be long as the light of the surrounding may be too dark. It all depends on what the photographer wants and whether if the available light allows him to do what he wants.
 

Ian

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Feb 20, 2002
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#4
Originally posted by sprockett
hi, i see so many put the aperture size in different terms from the f2.8, blah blah etc like on my S45...

f2.8 stands for wat size ah? i know its the biggest but what is the actual size?


i see b4 some pple got put aperture size 15, 10, etc... what is that in the fxxx terminology?

pls advise.. thanks bros!
Aperture in optical mechanics is directly related to the focal length of the lens and it's physical size can be calculated by the following formula.

Aperture Size in mm = Lens focal length / aperture number.

So a 50mm lens having an aperture of f2.0 has an aperture diameter of 25mm.

However, it gets a bit more complex with camera lenses, as a camera lens's focal length is not always it's genuine optical focal length, but can be engineered by clever design to be an 'equivalent' length. This type of engineering is often found in some of the newer compact zoom lenses where the focal length is longer than the actual lens.

What is more important to really understand is the relationship between aperture and the amount of light transmitted through the lens. A change of one "stop" in aperture, eg: f2.8 to f4 results in one half the light being transmitted. Conversly changing the aperture from f16 to f11 allows twice the amount of light to pass. This is because the area of the apterture has been doubled or halved (based on the square root of 2).

If you have more questions feel free to ask and I'll do my best to answer them in a non confusing manner.
 

Ian

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Feb 20, 2002
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#5
Originally posted by excentrique
Okay I'm gonna give a shot trying to explain what aperture means.
Erm I'd suggest you stick to the artsy fartsy side of photography as your showing a distinct lack of understanding of DOF, how it's calculated and apertures :) (grin how could I resist)

Merry Xmas Exe.
 

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