What is the difference between the F stop?


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SilverIce

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Aug 16, 2008
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#1
What is the difference in btw the F stop? lets say the f/2.8 and f/4....
What i know is the bokeh, and the 2.8 would be better to use at nite when it is in a low light condition..

I heard tat 2.8 is a fast lens but fast in wat way?
What are all the difference between the F stop? Hope someone can answer me..
 

Virgo

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Dec 23, 2003
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#2
The difference in f-stop is how wide the aperture of the camera opens. f2.8 opens bigger than f4 of course, and thus allows more light to enter the camera.

A 'fast' lens meaning it offers larger aperatures (smaller f-stop values) so that you can still take picures in low light conditions and yet maintaining a comfortable shutter speed for sharp pictures.

These are basics which you need to go read up further.
 

#3
What is the difference in btw the F stop? lets say the f/2.8 and f/4....
What i know is the bokeh, and the 2.8 would be better to use at nite when it is in a low light condition..

I heard tat 2.8 is a fast lens but fast in wat way?
What are all the difference between the F stop? Hope someone can answer me..
hi as for your question i will try to ans it , if wrong someone pls correct me :)

#1 yes lens like F1.2 , 1.4 , 1.8 and 2.0 do have very nice bokeh .

#2 the difference in F1.4 is brighter thanF1.8, F4 and so on , and it allow u to get faster shutter speed in low light

#3 even if it F2.8 in lowlight u may need a flash to freeze the motion if the subject is moving coz the shutter speed is not fast enuff .

hope it ans your question :)
 

two200

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Nov 19, 2004
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#5
..... and this ;)

In short:
f number is inversely proportional to the aperture, hence smaller f number bigger aperture
bigger aperture affect 3 things:

1. amount of light, hence bigger aperture more light therefore faster shutter speed (= "faster" lens)

2. depth of field, bigger aperture narrow depth of field, meaning only things focused by AF will be in focus whereas background will be blurred. (Remember pinhole camera in school?)

3. as explained above, the shutter speed because shutter speed and aperture determine the amount of light on the sensor. Hence bigger aperture, shorter shutter speed to get same amount of light as smaller aperture and longer shutter speed
 

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J-Chan

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Sep 21, 2005
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#6
faster in the sense that at the same ISO, a f/2.8 aperture would give a faster shutter speed than f/4..
 

checkers

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Aug 18, 2008
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#7
What is the difference in btw the F stop? lets say the f/2.8 and f/4....
What i know is the bokeh, and the 2.8 would be better to use at nite when it is in a low light condition..

I heard tat 2.8 is a fast lens but fast in wat way?
What are all the difference between the F stop? Hope someone can answer me..
You should go read up on light & camera.
 

SilverIce

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Aug 16, 2008
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#8
Tks for all replies..
Especially zac08 and two200 for the links..

I think i understanding better now..
 

wootsk

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Aug 12, 2007
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#9
Low F- Stop doesn't totally means a faster lens as in the lens is faster in what ever way.

Lower f-stop just means more light can enter and so more brighter
It means you MIGHT be able to shoot in low light without flash
It means you MIGHT be able to shoot with a faster shutter speed
It means you MIGHT be able to shoot with lower ISO value

The above mention are just some example. Most important is that you have to be used to your gears and light. Understand how light works
Now all theory but no example is a bit hard.
Lets say you are shooting a night scenary. You might use a lower f-stop value rather then the higher ISO value to shoot so that it is not that dark
But if you are shooting a night scenary with a model (might be your gf) infront, you want a nice bokeh. You might think that using just lower f-stop value u can shoot a nice picture. You are wrong, cause light travels from the background to your model back to your camera. what you might see is a nice background and a heavily underexpose model. So you need a flash, preferable a flash with a bounce card. Don't worry about the background as I nv see a flash that powerful yet. :p
Hope it helps

F- stop fomule and theory can be found at http://en.wikipedia.org/wiki/F-number
 

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