how to judge what F stop (apperture) to use?


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orionct

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Jun 24, 2009
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#1
Hi friends,

One question in mind, how should i judge what F stop no (apperture) to use when taking picture.
I only know we can use smallest f number (biggest apperture) so that the focus is in the front object and have more "bokeh" effect behind. (like f1.8 to f3.2 for example)

But how you jugde what f no for far object?
My question is, how you know if either f9, f10 or f22 is good? how to determine this no for far object? :think:
 

Rashkae

Senior Member
Nov 28, 2005
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#2
F stop affects depth of field. This IS NOT the same as "focus distance". I suggest you try re-reading a bit more on it. You can use any aperture for objects near or far, the difference will be how much of it is in focus.

Adjusting f stop does NOT shift your focal point back or forth. F is not for "focus".
 

Nov 9, 2007
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#3
Hi Some quick notes

1. Depending on Depth of field which is the range in focus, you can check DOF here (http://www.dofmaster.com/doftable.html)
2. Depending on the sharpness you want to achieve, normally the sharpest image is at 2-3 stop from the biggest apperture of the lens 
3. Depending on light condition, for indoor, no flash, a maximum aperture 2.8 is required for many cases

The minimum focus distance is fix for each len
 

orionct

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Jun 24, 2009
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#4
F stop affects depth of field. This IS NOT the same as "focus distance". I suggest you try re-reading a bit more on it. You can use any aperture for objects near or far, the difference will be how much of it is in focus.

Adjusting f stop does NOT shift your focal point back or forth. F is not for "focus".
Hi Rashkae, may be i don't know how to ask the correct question. I know f is not focus. But to take a good photo of far object, what apperture should we choose? base on feeling ? base on experience ? or is there a certain range you use ?
 

Galdor

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Jul 5, 2006
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#7
Hi Rashkae, may be i don't know how to ask the correct question. I know f is not focus. But to take a good photo of far object, what apperture should we choose? base on feeling ? base on experience ? or is there a certain range you use ?
There really isn't a fix setting to use. Some people will use a 200mm @ f2.8 while some will use f4 or f8 or even f11 or f13. It all depends on what you want to achieve.
 

#8
there is no standard rules, but these are as a guide.

for landscapes, F8 or F11, so that most of the scene are in focus.
for portrait(one person), F4 or more, unless u want certain parts like the eyes to be in focus and the rest of the body to be OOF.
for portrait(a group), usually use F5.6 or more so that everyone is in focus.
for macro photography, usually use big F stop like F16 onwards, so that there is a thinner DOF.
 

Octarine

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Jan 3, 2008
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#9
Hi Rashkae, may be i don't know how to ask the correct question. I know f is not focus. But to take a good photo of far object, what apperture should we choose? base on feeling ? base on experience ? or is there a certain range you use ?
Aperture is a part of the "exposure equation". the available light, your intended shutter speed and the available / usable ISO speed will give you a range of usable aperture values. Together with your intended compositions (shallow / deep DOF) you need to make the necessary adjustments. The distance between subject and background has a big role in creating background blur. No point using f/1.8 if your object is 20cm in front of a wall but 10m away from you.
 

ZerocoolAstra

Senior Member
Mar 13, 2008
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#10
Hi Rashkae, may be i don't know how to ask the correct question. I know f is not focus. But to take a good photo of far object, what apperture should we choose? base on feeling ? base on experience ? or is there a certain range you use ?
There's a bit of confusion as to the actual point of your question.
The general assumption made is that you want BOTH the near and distant object to be in focus, in which case the depth of field (caused by the aperture opening) comes into play.
However, if you ONLY want to focus on the far object, you can still use a large aperture and have the object in focus.

For example if you have a 300mm f/4 lens, and you want to photograph the top of Swissotel Stamford from the ground, you can use f/4 and auto/manual focus such that the top floor is sharp. Not a problem.

So to take "good photo of far object", there is no fixed aperture to use.
To have a photo where the subject and background are both sharp, then you need to understand how much of a depth of field you need.
Aperture and camera-subject-background distance both play an important role.

hope that helps.
 

J-Chan

Senior Member
Sep 21, 2005
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#11
use the much under-utilised DoF priority mode, should be labelled A-DEP or something similar on the mode dial..

depending on the cam model, either it uses all its focusing points and tries to get everything in the DoF or you can focus on the close object then the far and the cam spits out an aperture reading to make those 2 points in the DoF..

hope that answers your qns.
 

orionct

New Member
Jun 24, 2009
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#12
there is no standard rules, but these are as a guide.

for landscapes, F8 or F11, so that most of the scene are in focus.
for portrait(one person), F4 or more, unless u want certain parts like the eyes to be in focus and the rest of the body to be OOF.
for portrait(a group), usually use F5.6 or more so that everyone is in focus.
for macro photography, usually use big F stop like F16 onwards, so that there is a thinner DOF.
ok, noted ...good reference for me, thanks a lot!
 

orionct

New Member
Jun 24, 2009
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#13
There's a bit of confusion as to the actual point of your question.
The general assumption made is that you want BOTH the near and distant object to be in focus, in which case the depth of field (caused by the aperture opening) comes into play.
However, if you ONLY want to focus on the far object, you can still use a large aperture and have the object in focus.

For example if you have a 300mm f/4 lens, and you want to photograph the top of Swissotel Stamford from the ground, you can use f/4 and auto/manual focus such that the top floor is sharp. Not a problem.

So to take "good photo of far object", there is no fixed aperture to use.
To have a photo where the subject and background are both sharp, then you need to understand how much of a depth of field you need.
Aperture and camera-subject-background distance both play an important role.

hope that helps.
hi zero, i think my question is hard to answer. haha, i should not say to take good photo because different depth of field present different feeling of good.

i should just ask how normally people decide what f stop to choose and why they use that no?

anyway, thanks for your explanation.
 

zac08

Senior Member
Feb 21, 2005
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#14
hi zero, i think my question is hard to answer. haha, i should not say to take good photo because different depth of field present different feeling of good.

i should just ask how normally people decide what f stop to choose and why they use that no?

anyway, thanks for your explanation.
personal preferences...

and how you want the image to be portrayed. If you want a dreamy effect where only the subject is in focus with the rest blur, then use a large aperture. If you want more of the picture to be in focus like in landscapes, then use smaller apertures. Just use the correct one for your requirements. ;)
 

wildcat

Senior Member
Sep 8, 2004
3,269
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#16
there is no standard rules, but these are as a guide.

for landscapes, F8 or F11, so that most of the scene are in focus.
for portrait(one person), F4 or more, unless u want certain parts like the eyes to be in focus and the rest of the body to be OOF.
for portrait(a group), usually use F5.6 or more so that everyone is in focus.
for macro photography, usually use big F stop like F16 onwards, so that there is a thinner DOF.
Think this is a useful rough guide for a newbie like me too. If I may ask further, for night scenes and sports, can I say usually as big as aperture as possible (f2 or f2.8) so that as much light go in as possible for the faster possible shutter speed?
 

ZerocoolAstra

Senior Member
Mar 13, 2008
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#17
Think this is a useful rough guide for a newbie like me too. If I may ask further, for night scenes and sports, can I say usually as big as aperture as possible (f2 or f2.8) so that as much light go in as possible for the faster possible shutter speed?
Usually for night scenes, a tripod is used. Thus a long exposure is not a problem, and a large aperture is unnecessary.
For example, most of my night landscapes are taken at about f/7.1-f/8, for up to a few seconds exposure. Doesn't need a fast lens.
 

#18
Think this is a useful rough guide for a newbie like me too. If I may ask further, for night scenes and sports, can I say usually as big as aperture as possible (f2 or f2.8) so that as much light go in as possible for the faster possible shutter speed?
as i mentioned before, yes, it is just a rough guide. doesnt means those photos shoot with F4 are bad photos.

for night photography, if u talking about landscapes/cityscapes, it is always good to shoot at F8 or more, as u want almost everything in focus. and because u r shooting at F8 or more, the shutter is usually a few secs... ranging from 5sec to 30sec etc. and because of that, it is adviceable to use a tripod. btw, night scene if possible use the lowest ISO, which maybe 50 or 100 depends on yr camera.

for sport, u need fast lens or prime lens if u want to capture motion freeze. as the motion freeze usually freeze at 1/125 or 1/200 or more. and for sport photography, most of the time, u want the subject to be in focus or standout from the rest in the photos, so a big aperture is needed.

for sport, there is also times when u want to so-called capture movement(motion blur), then u may need to shoot less than 1/30 etc. and panning shots also need slower shutter speed.

btw, what i mentioned, are usually shooting modes like aperture priority or shutter priority, where u only need to worry about either shutter speed or aperture. cos in manual mode, u need to calculate the aperture, shutter speed yrself.
 

Last edited:
#19
F-stop does not affect focusing distance.

Focusing distance: It is the distance between the lens and the object.
F-stop: It is the aperture. It affects the depth of field of the objects and the background.
 

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