Explain about F/ number for aperture


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Jark89

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Can anyone explain to me about the f/ no. for apertures such as f2.0, f4.5.
i really dun understand what it means and how to use it..
thanks
 

night86mare

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Wince, that's true.

K but anyways, to save the poor hapless soul;
f/stop number is simply the reverse, ie. if you want a BIGGER HOLE (or aperture), then you need a SMALLER f/stop number. If you want a SMALLER hole (or aperture) , then you need a BIGGER f/stop number.

Aperture is all to do with light and depth of field, among other things. Er, if I go on writing I can write an entire tutorial, so like evenstar says, google and wiki are your new best friends for now!

Or you can check out the newbies corner STICKY by Zoosh, which is erm, there for a big reason. Because it's informative and good.
 

Hobbesyeo

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loadingbay

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Have a look here:http://www.photoxels.com/tutorial_aperture.html

Or you can also start from scratch here: http://www.photoxels.com/digital-photography-tutorials.html

These are quite good places to start from. The public library also has alot of books about basic photography concepts that you can also learn from.

Good luck! ;)
:thumbsup: :thumbsup: This is a good.....thks for sharing.
 

nikonrus

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One thing you might wana know (if you haven't noticed before) ..... the smaller the f number (we sometimes use the term fast for apature as well; ie f2.0 is a relatively fast lens & f1.2 is a very fast lens), the more expensive it gets.
 

asterixsg

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#8
Bro,
May I also suggest that you get a copy of Bryan Peterson's book titled "Understanding Exposure". It not only tells you about aperture, there is clear explanation of shutter speed, ISO etc. etc. Its a book worth buying. I think zoossh has mentioned in his post, but this might've got buried in the wealth of info that he has put there.
Cheers.
 

surge

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#9
technically, i think it has to do w the diameter of a lens and its focal length to get a correct focus. please correct me if i am wrong

i think its the size of the barrel ( thus the front element of the lens) is derive by focal length/aperture. thus for a 200mm@2.8, the front element will be at least a 71mm in diameter.

which explains why long lens at large aperture are very big due to the front element.

shooting wise, f2,2.8,4,5.6,8,16 etc just means at each stop, the opeing is twice as big and it allows twice as much light to enter.

so double the shutter then half the aperture and vice versa
 

windoze

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Feb 26, 2007
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#10
Can anyone explain to me about the f/ no. for apertures such as f2.0, f4.5.
i really dun understand what it means and how to use it..
thanks
HI, im no expert - as a matter of fact im a slow learner but im goona go out on a limb here ( my shrink would be so happy with me ) and try to explain what i know or think i know.
the size (opening) of the aperture determines how much light, ie the quantity of light, that will reach the media ( cf card etc. ) you use to record an image. The wider the aperature, the more it is open and the more light that can reach the media. The smaller the aperature, the less wide it is open and therefore the less light that can reach the media. So what you dare say?? well the fact is that the quantity of light that reaches the media is not only a necessary ingredient for a properly exposured image to happen but the quantity of light also affects depth of field. You know those beautiful pictures you see of flowers or birds that are so sharp with a background that seems blurried, well that has to do with depth of field. do you like those images where the trees in the background are nearly as sharp as the people swimming in the lake, well that too has to do with depth of field. your choice of aperture can affect depth of field. Anyway we have a scale that denotes the size of the aperture opening, and we call it the f- stop scale. Commit these f-stops to memory. you can thank me later, f/2, f/2.8, f/4. f/5.6, f/8
lets talk about this "f-ing" scale a bit... ;)
DONT WORRY ABOUT THE ACTUAL NUMBERS!!! DONT TRY TO FIGURE WHERE THEY COME FROM. THESE ARE THE F-STOPS AND THATS IT!
( umm, actually i lied, there are other f-stops, but for now the ones i listed are most important)
f/2 is a wider opening than f/4, f/4 is a wider opening than f/5.6, f/5.6 is a wider opening than f/8 yadda yadda ......
the smaller the number the wider the opening!!!! why do you care? if you need more light use a smaller f-stop. maybe your shutter is closing so fast ( another story for another time ) , the extra light is needed for that "properly exposed image.The math that goes into the formula for f-stops is complicated and it may not seem rational BUT IT IS! i gave you a series of f-stops above. As you go from one f-stop to another in sequence, one half the light becomes available. so the amount of light available at f/4 is half the amount available if you used f/2. and yea the amount of light hitting the media at f/5.6 is half the amount that hits it at f/4 and 1/4 the amount that hits it at f/2. This will all become understandable as you now read more on your own.
so in conclusion you need f-stops to know how much light to send to the media ( you'll really need this info when you learn about shutter speeds ).
you also need to know f-stops to control depth of field ( look that up ) and finally...
it is a given ( from what ive heard ) that a lens is sharper about two stops down from its widest opening! Yo!!! did you hear this? I just showed you how to get a sharper image. if your lens is a f/4 lens, try "stopping it down" to f/8 and see what happens! Look at us using photog lingo!! now we can "step down" which means closing the aperture more to let in less light. AND i might do this to get a narrower depth of field. More of my image is looking focused and sharp. Yippee!! I almost understand what Im talking about. I left out a lot of stuff and i dont even know if what i said is accurate, but ya know what? this incomprehensible rant helped me!!!!



troy
 

#11
HI, im no expert - as a matter of fact im a slow learner but im goona go out on a limb here ( my shrink would be so happy with me ) and try to explain what i know or think i know.
the size of the aperture determines how much light, ie the quantity of light, that will reach the media you use to record an exposure. The wider the aperature, the more it is open and the more light that can reach the media. The smaller the aperature, the less it is open and the less light that can reach the media. So what you dare say?? well the fact is that the quantity of light that reaches the media is not only a necessary ingredient for an exposure to happen but the quantity of light also affects depth of field. You know those beautiful pictures you see of flowers or birds that are so sharp and the background seems blurried, well that has to do with depth of field. ok, back to aperture. Anyway we have a scale that denotes the size of the aperture opening, and we call it the f- stop scale. Commit these f-stops to memory. you can thank me later, f/2, f/2.8, f/4. f/5.6, f/8

f/2 is a wider opening than f/4, f/4 is a wider opening than f/5.6, f/5.6 is a wider opening than f/8 yadda yadda ......
the smaller the number the wider the opening!!!! why do you care? need more light use a smaller f-stop. The math that goes into the formula for f/stops is complicated and it may not seem rational BUT IT IS! i gave you a series of f-stops above. As you go from one f-stop to another in sequence, one half the light becomes available. so the amount of light available at f/4 is half the amount available if you used f/2. and yea the amount of light hitting the media at f/5.6 is half the amount that hits it at f/4 and 1/4 the amount that hits it at f/2. This will all become understandable as you now read more on your own.
so in conclusion you need f-stops to know how much light to send to the media.
you also need to know f-stops to control depth of field ( look that up ) and finally...
it is a given ( most of the time ) that a lens is sharper about two stops down from its widest opening! Yo!!! did you hear this? I just showed you how to get a sharper image. if your lens is a f/4 lens, try it at f/8 and see what happens! I left out a lot of stuff and i dont even know if what i said is accurate, but ya know what? It helped me!!!!



troy
Not entirely correct but some information is in there.
 

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