Apperture, shutter speed and exposure


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johnmaeda

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Dec 16, 2007
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#1
Hi guys,

I have a question on aperture, shutter speed n exposure.

For this wide angel photo I have taken,



I was advice by fellow CS member Hosea to try a smaller aperture # range (e.g.F8-F16@low ISO with tripod)

My question wld be what wld be e reason for dat?? If a aperture of F5.6 wld do the job, y bother to go up to F8/ F16?

I understand abt the iso part but its the aperture part which I am nt sure abt.

Hope that someone can advice me on this

Thanks :)
 

wdEvA

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Sep 1, 2006
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#2
having a lower aperture will allow you to have a slower shutter speed, which will create starlight effect on those lights, low ISO will result in less noise.
 

Rashkae

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Nov 28, 2005
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#3
For one thing, you increase the DOF and improve sharpness. Also, you de-circle the aperture blades, resulting in a "star" pattern on the lights.
 

flipfreak

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#4
if u stop down more, the dof increases so more of the total landscape is sharper as compared to using a f/5.6. but the shutter speed increases as a result of using a smaller aperture so the tripod might be necessary. and since its gonna be on tripod, might as well shoot at lowest iso right? :D
 

dOlBy

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Jan 7, 2004
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#5
Simple explanation, use smaller aperture to get everything in focus(increase DOF)
 

johnmaeda

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#6
having a lower aperture will allow you to have a slower shutter speed, which will create starlight effect on those lights, low ISO will result in less noise.
For one thing, you increase the DOF and improve sharpness. Also, you de-circle the aperture blades, resulting in a "star" pattern on the lights.
if u stop down more, the dof increases so more of the total landscape is sharper as compared to using a f/5.6. but the shutter speed increases as a result of using a smaller aperture so the tripod might be necessary. and since its gonna be on tripod, might as well shoot at lowest iso right? :D
Thanks for the clarification.

Juz to sum up what you guys have said,

In order to achieve the starlight effect, a slower shutter speed has to be used, which wld result in a greater f-stop

AND

The result of a lower ISO wld be either a slower shutter speed or a greater f-stop which wld in the end also get a slower shutter speed and greater f-stop.

Right?
 

refraXion

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Mar 24, 2008
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#7
I think you understood it the other way round.

In order to achieve the starlight effect, a larger f-stop has to be used, and thus a slower shutter speed is required in order to achieve the same exposure. :)

As for ISO, boosting the ISO will result in more noise. So to reduce this noisy effect, use a lower ISO, and to compensate for that, a longer shutter speed is required once again to achieve the same exposure.

Correct me if I'm wrong, I'm learning too. :)
 

dOlBy

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#8
...
The result of a lower ISO wld be either a slower shutter speed or a greater f-stop which wld in the end also get a slower shutter speed and greater f-stop.

Right?
The most important thing about using low ISO is to reduce noise.
 

johnmaeda

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Dec 16, 2007
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#9
I think you understood it the other way round.

In order to achieve the starlight effect, a larger f-stop has to be used, and thus a slower shutter speed is required in order to achieve the same exposure. :)

As for ISO, boosting the ISO will result in more noise. So to reduce this noisy effect, use a lower ISO, and to compensate for that, a longer shutter speed is required once again to achieve the same exposure.

Correct me if I'm wrong, I'm learning too. :)
Actually, I think u n i are toking abt the same thing but mayb my eng nt so powderful only.

Wahahaha. :bsmilie:

Juz dat it shld be called the correct exposure instead of "same exposure", unless the photographer chooses to do bracketing. Right?

Correct me if im wrong, coz i suppose i don't have some of the photography terms correct
 

yannh

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Dec 10, 2007
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#10
2 more advantages for using smaller aperture:
* Every lens have their sweet spot, means the sharpest image obtained from a range of aperture size. And it's usually not at wide open.
* For wide angle, if aperture is big, light may fall of to the edge. So you may get different brightness across your image.
 

catchlights

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Sep 27, 2004
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#11
I think you understood it the other way round.

In order to achieve the starlight effect, a larger f-stop has to be used, and thus a slower shutter speed is required in order to achieve the same exposure. :)

As for ISO, boosting the ISO will result in more noise. So to reduce this noisy effect, use a lower ISO, and to compensate for that, a longer shutter speed is required once again to achieve the same exposure.

Correct me if I'm wrong, I'm learning too. :)
a larger f stop means larger "hole", the number of f stop is in fraction, eg, 1/5.6, 1/8, 1/11, the larger number at below, also means smaller in actual figures.

lower ISO does have lower noise, however, if the exposure time too long, like 20 sec or 30 sec and above, (depends the cameras) also will have higher noise level in longer exposure time.
 

johnmaeda

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#12
2 more advantages for using smaller aperture:
* Every lens have their sweet spot, means the sharpest image obtained from a range of aperture size. And it's usually not at wide open.
* For wide angle, if aperture is big, light may fall of to the edge. So you may get different brightness across your image.
Thanks for the advice.

Now Im clearer as to the benefits of a smaller aperture.
 

catchlights

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#13
Thanks for the clarification.

Juz to sum up what you guys have said,

In order to achieve the starlight effect, a slower shutter speed has to be used, which wld result in a greater f-stop

AND

The result of a lower ISO wld be either a slower shutter speed or a greater f-stop which wld in the end also get a slower shutter speed and greater f-stop.

Right?
for an example, to get a desire exposure of a scene, you are using ISO 400, f4, 1/60sec,

if you change the ISO to 200, you need to change the aperture or speed or both to get the same exposure value, eg, [ISO 200, f2.8, 1/60sec], [ISO 200, f4, 1/30sec] or [ISO 200, f3.5, 1/45sec] are having the same exposure value.
 

fergo

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Mar 19, 2007
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#14
basically, a large aperture number will give you overall sharpness of the shot. especially in this shot, as its a landscape. small aperture numbers are usually used for portraits etc. where background blur out which give the subject more 'focus'.

imagine taking a landscape shot of a city. with buildings in the distance(focus point) and some in the foreground. if you were to use f5.6, the foreground would be slightly blur as compared to those in the distance. with a larger aperture setting and the same focus point which in this case the buildings in the background, the overall picture will be sharper from foreground to background.

just my 2 cents worth. ;)

P.S i'm no pro.. still new. pls correct me if i'm wrong. :thumbsup:
 

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