lenses and aperture settings


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Jan 4, 2008
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Hi, I'm a newbie here and this is my first posting. Got a dumb :confused: question here relating to the f numbers in lenses and the f numbers you set in your camera for the desired aperture size. What is their relationship? The selection for aperture size is from the camear dial, from very large aperture to very small aperture. But what has the lens f numbers got to do with the aperture size you are selecting in your camera? Why some lenses are f2.8 and others range from f3.5 - 5.6? How does it affect my aperture selection? By the way, I just bought a Nikon D40X, and using the kit lens.
 

dotaboy

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#2
Hi, I'm a newbie here and this is my first posting. Got a dumb :confused: question here relating to the f numbers in lenses and the f numbers you set in your camera for the desired aperture size. What is their relationship? The selection for aperture size is from the camear dial, from very large aperture to very small aperture. But what has the lens f numbers got to do with the aperture size you are selecting in your camera? Why some lenses are f2.8 and others range from f3.5 - 5.6? How does it affect my aperture selection? By the way, I just bought a Nikon D40X, and using the kit lens.
Higher the aperture value,the smaller lesser the light are able to enter.
That means,wider aperture=more expensive
 

Redsun

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Hi, I'm a newbie here and this is my first posting. Got a dumb :confused: question here relating to the f numbers in lenses and the f numbers you set in your camera for the desired aperture size. What is their relationship? The selection for aperture size is from the camear dial, from very large aperture to very small aperture. But what has the lens f numbers got to do with the aperture size you are selecting in your camera? Why some lenses are f2.8 and others range from f3.5 - 5.6? How does it affect my aperture selection? By the way, I just bought a Nikon D40X, and using the kit lens.
basically,the smaller the F number eg 2.8 the bigger the hole of the aperture which in turn allows more light though and allows you to use a faster shutter speed
for lens which state F3.5 - F5.6,lets take your kit lens as example
It means at 18mm the smallest F-stop is F3.5,at 55mm the Smallest F-stop is 5.6
The bigger the F stop,the less light it allows through the lens
 

canonG9

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Dec 4, 2007
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hi,

this is my understanding of aperture

a smaller f number would mean that the aperture is much larger, hence more light can get in, and u can use a faster shutter speed to capture the image..

a larger f number would mean that the aperture is smaller, hence less light can get in, and u have to use a slower shutter speed...

Simple analogy..

assuming that the bucket is 5L (ie: camera sensor) and water (ie: light) is at constant flow(ie: shutter speed), a larger diameter hose (larger aperture ; smaller f number) would be able to fill up the bucket much faster as compared to a smaller diameter hose (smaller aperture; larger f number)

uses of aperture (at least the way i use it) :
Larger aperture (smaller f number) can give you those blurred background shots when empasis is placed on the subject rather than the whole image (eg : potraits)

Smaller apertures will give you clear image from front to back, like when you are taking landscape, scenery shots..

if i am not wrong, 2 different lens with the same f number does not mean that the aperture is of the same size.. i believe it has some relationship with the focal length of the lens...

you can try to read http://en.wikipedia.org/wiki/Aperture .. it has some pics to show the difference of the images at different f numbers (f-stop), and perhaps a clearer explaination
 

Jan 4, 2008
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basically,the smaller the F number eg 2.8 the bigger the hole of the aperture which in turn allows more light though and allows you to use a faster shutter speed
for lens which state F3.5 - F5.6,lets take your kit lens as example
It means at 18mm the smallest F-stop is F3.5,at 55mm the Smallest F-stop is 5.6
The bigger the F stop,the less light it allows through the lens
uhmm.. lets see if I understand. You mean at 18mm my camera will not allow me to go beyond a bigger aperture than F3.5? And at 55mm, the camera will not allow me to have a bigger apperture than F-stop 5.6? All these is despite turning the dial while in Aperture Mode? :think:
 

zac08

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Feb 21, 2005
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uhmm.. lets see if I understand. You mean at 18mm my camera will not allow me to go beyond a bigger aperture than F3.5? And at 55mm, the camera will not allow me to have a bigger apperture than F-stop 5.6? All these is despite turning the dial while in Aperture Mode? :think:
yup.

That's the physical limitation of the lens that you have. The lenses with a constant aperture actually allows the aperture to widen at the zoom part to allow more light to enter and thus still maintain a constant large aperture.
 

Fragnatic

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Jan 24, 2008
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#7
uhmm.. lets see if I understand. You mean at 18mm my camera will not allow me to go beyond a bigger aperture than F3.5? And at 55mm, the camera will not allow me to have a bigger apperture than F-stop 5.6? All these is despite turning the dial while in Aperture Mode? :think:
yep, u got it right.

for lenses with a range of f-values, means that's the largest f-number for the widest to the most tele would be that range. any focal length in-between would have a largest f-number of somewhere in-between that stated range too.

for a constant aperture lens like a f/2.8 lens, the largest aperture possible is f/2.8 and no larger. and it maintains that max aperture size no thoughout all its focal length.

of cos, u can stop down the aperture but the stated f-numbers would be the maximum u can go (smallest f-number).
 

Jun 12, 2005
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1) You set the aperture of the lens via the controls on the camera.

2) Aperture is the opening of the diaphame on the lens to control the amount (intensity) of light reaching the senor/film.

3) optical effects of the aperture on the lens is the different amount of "depth-of-field" you get in the picture, i.e the amount of reasonable sharpness in the picture. smaller aperture (bigger f number) = more depth-of-filed; bigger aperture opening (smaller number) = less depth-of-field.

4) zoom lenses have fix aperture and variable aperture. fix aperture (more expensive) lenses does not vary in maximum aperture size when you zoom in or out; variable aperture lenses have a bigger maximum aperture when used in wide angle, smaller maximum aperture when zoom in to longer focal length.
 

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yep, u got it right.

for a constant aperture lens like a f/2.8 lens, the largest aperture possible is f/2.8 and no larger. and it maintains that max aperture size no thoughout all its focal length.

of cos, u can stop down the aperture but the stated f-numbers would be the maximum u can go (smallest f-number).
That's a lot of learning here. BTW when you say 'stop down the aperture' you mean ... reducing the aperture as in moving from f/2.8 to say f/5.6 by turning the camera dial when in Aperture Mode? And it will not allow you to increase aperture beyond f/2.8 right? So I guess it is a fast lens because it has a larger aperture, and more costly.

I don't own a f/2.8 but would like to have one in the future. But let me finish my basic photography class and see how it goes.
 

Jan 4, 2008
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#10
1) You set the aperture of the lens via the controls on the camera.


4) zoom lenses have fix aperture and variable aperture. fix aperture (more expensive) lenses does not vary in maximum aperture size when you zoom in or out; variable aperture lenses have a bigger maximum aperture when used in wide angle, smaller maximum aperture when zoom in to longer focal length.
Hi.. this is getting very interesting. So am I correct to say for fix aperture lenses eg f/2.8 you cannot vary 'maximum' aperture size but you can vary 'minimum' aperture size via the controls of the camera?
 

Jun 12, 2005
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#11
max aperture is the biggest aperture of the lens. which means you can "open" your lens to that max. for variable aperture lens, as you zoom in/out, the max aperture vary (if you ahve selected the max aperture).

min aperture is the smallest aperture your lens can close to. you can only use aperture settings between the max and min of your lens.
 

Fragnatic

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Jan 24, 2008
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#12
Hi.. this is getting very interesting. So am I correct to say for fix aperture lenses eg f/2.8 you cannot vary 'maximum' aperture size but you can vary 'minimum' aperture size via the controls of the camera?
hmmm.. don't think too much.
for that f/2.8 lens, it just means the largest u can ever go is f/2.8... of cos if u want, u can set to any aperture smaller than f/2.8, like f/4, f/5.6, f/8, etc...

i mean, when u shoot, u can only select 1 aperture value per shot right? (for single exposure photo). no nd to compare whether u can vary max/min or not. its not a range of apertures that u are using when shooting 1 shot right?

unless u are talking abt max possible and min possible aperture. not sure abt ur nikon kit lens, but for my canon 17-85 f/4-5.6 lens,
at 17mm, max: F/4, min: f/22 --> means if i use 17mm, i can select any aperture frm f/4 - f/22.
at 85mm, max: f/5.6, min f/32 --> means if i use 85mm, i can select any aperture frm f/5.6 - f/32.

looking at the canon 70-200 F/4L, it has a constant aperture and its stated max aperture is f/4. and u can set frm f/4 to f/32 for focal lengths 70 to 200mm (any range in between can have f/4 - f/32).
 

Jan 4, 2008
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hmmm.. don't think too much.
for that f/2.8 lens, it just means the largest u can ever go is f/2.8... of cos if u want, u can set to any aperture smaller than f/2.8, like f/4, f/5.6, f/8, etc...

i mean, when u shoot, u can only select 1 aperture value per shot right? (for single exposure photo). no nd to compare whether u can vary max/min or not. its not a range of apertures that u are using when shooting 1 shot right?

unless u are talking abt max possible and min possible aperture. not sure abt ur nikon kit lens, but for my canon 17-85 f/4-5.6 lens,
at 17mm, max: F/4, min: f/22 --> means if i use 17mm, i can select any aperture frm f/4 - f/22.
at 85mm, max: f/5.6, min f/32 --> means if i use 85mm, i can select any aperture frm f/5.6 - f/32.

looking at the canon 70-200 F/4L, it has a constant aperture and its stated max aperture is f/4. and u can set frm f/4 to f/32 for focal lengths 70 to 200mm (any range in between can have f/4 - f/32).
hi.. I am so encouraged by the response in this forum, and the patience shown in the explanation... so here's a big :thumbsup: for all who took time to reply. I am not technically inclined and numbers baffle me. But I am interested in making art out of photography and that explains why I am here. :D
 

Fragnatic

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#14
hi.. I am so encouraged by the response in this forum, and the patience shown in the explanation... so here's a big :thumbsup: for all who took time to reply. I am not technically inclined and numbers baffle me. But I am interested in making art out of photography and that explains why I am here. :D
haha..

just enjoy shooting with ur new equipment!
play around the settings and u'll get better. also, to do some read up. there are some very useful guides in the forum. under newbies corner > articles and guides.
 

liarliar

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#17
But that doesn't mean smaller aperture is undesired. I would like some starry effects on a lens at f/22 when telephoto
 

Jan 4, 2008
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#18
But that doesn't mean smaller aperture is undesired. I would like some starry effects on a lens at f/22 when telephoto

Hi.. pl tell me more about 'starry effects' :bigeyes:. Are you referring to eg. night shots taken with that special glow in street lamps? How to achieve that? :think:
 

Fragnatic

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#19
Hi.. pl tell me more about 'starry effects' :bigeyes:. Are you referring to eg. night shots taken with that special glow in street lamps? How to achieve that? :think:
use as small an aperture as possible. (high f-number)
like f/22, f/32, etc...

the number of pointed tips of the "star" would be the number of aperture blades in the lens.



of cos, if u want to achieve that effect with larger aperture, the star effect would not be very obvious (the pointed tip would be shorter and blurrer. unless u use a star filter (think its called this way).
 

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