F2.8 Question


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pikapig

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#1
I see alot of people are recommending tamron 17-50mm f2.8 vs kit lens 18-55mm for canon and the main reason was because of the constant aperture F2.8. (Leaving aside the IQ and performance of this lens)

They often quoted that F2.8 is good for low light situation. My understanding is that aperture is more for DOF, no doubt we can use F2.8 at dim lighted area but wont the picture throw out shallow DOF?

For example, if i were to shoot indoor for a large group photo, would F2.8 become useful? What about night shooting of landscape with very minimum lighting at F2.8?
 

dorts

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Mar 10, 2007
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#2
Do you want a blur image with slow shutter speed, or slightly lesser DOF?

For wide angles, the problem with DOF usually is not that obvious or problematic. :)
 

catchlights

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#3
yes, using a large aperture will result in shallow depth of field, which not recommended to shoot group photo or landscape with wide open aperture.

however, such large aperture lens will help you in focusing at low light condition.
 

catchlights

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#4
Do you want a blur image with slow shutter speed, or slightly lesser DOF?

For wide angles, the problem with DOF usually is not that obvious or problematic. :)
please, not another "die die everything must shoot at f2.8, because I have a f2.8 lens"

TS is referring to group photo and landscape at night.

should use flash for the first situation.

a tripod for second situation.
 

2evans

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Nov 8, 2007
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#5
Exposure = ISO x Shutterspeed x Aperture

To get a "correct" exposure, If ISO and shutterspeed are limited, the only other value you can change is the Aperture. Hence, people recommend a zoom with F2.8.
 

Rashkae

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Nov 28, 2005
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#6
Actually, the Tamron is also very very very sharp. To me, that's more important than the larger aperture.
 

pikapig

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#7
please, not another "die die everything must shoot at f2.8, because I have a f2.8 lens"

TS is referring to group photo and landscape at night.

should use flash for the first situation.

a tripod for second situation.
You got me correct...yes..i was reading on tamron 17-50mm in some cs threads...shouldnt in low light situation for group shots you should rely on flash and on landscape using tripod with a longer shutter exposure? Why would people mentioning good f2.8 is good for low light situation? I thought it would be more correct to justify that a F2.8 can create a bokeh in low light situation.

I tried once under dim lightings to capture a new born baby potrait without the use of flash and the ending result was too shallow..
 

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pikapig

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#8
Actually, the Tamron is also very very very sharp. To me, that's more important than the larger aperture.
I agree the lens is very sharp...but the constant F2.8 is relatively useful as well.:)

Exposure = ISO x Shutterspeed x Aperture

To get a "correct" exposure, If ISO and shutterspeed are limited, the only other value you can change is the Aperture. Hence, people recommend a zoom with F2.8.
Noted this part...but provided the F2.8 zoom would not create a DOF that is too shallow on the subject..if that is the case..then no point to shoot under low light.
 

Rashkae

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Nov 28, 2005
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#9
I agree the lens is very sharp...but the constant F2.8 is relatively useful as well.:)



Noted this part...but provided the F2.8 zoom would not create a DOF that is too shallow on the subject..if that is the case..then no point to shoot under low light.
Well, you also need to understand that at wide-angle, f/2.8 does not generate a very shallow DOF at all
 

zac08

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Feb 21, 2005
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#10
I agree the lens is very sharp...but the constant F2.8 is relatively useful as well.:)



Noted this part...but provided the F2.8 zoom would not create a DOF that is too shallow on the subject..if that is the case..then no point to shoot under low light.
Go read more on DOF...

At different focal lengths as well as subject distance, you actually have quite a substantial window of sharpness...

Go look at my street shots, most of them are either shot at f2.8 or f1.8 when I am shooting with my 50mm lens.
 

styloe

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Jul 31, 2008
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#11
DOF from what I've learnt is factored by both aperture size and focal length. Try this website, Understanding Depth of Field in Photography. It's quite informative and technical (aka dry). :p

In my experience with my EFS 17-55, the shallow DOF out of f/2.8 is not a problem in indoor groupshots, due to the (wider) focal length required to fit everyone inside the frame. It gets more shallow only when you use the narrower end of the focal length.

For nightshooting of landscape, flash or stand is the logical approach, not aperture size. That's why I think the EFS10-22 (or most UWAs for that matter) is designed with f/3.5 widest.

Enjoy shooting! :)
 

navlem

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Sep 16, 2007
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#12
I agree the lens is very sharp...but the constant F2.8 is relatively useful as well.:)



Noted this part...but provided the F2.8 zoom would not create a DOF that is too shallow on the subject..if that is the case..then no point to shoot under low light.
DOF will not be too shallow at F2.8

Dun forget the tamron lens is quite wide, the shallow DOF is only a problem for longer range.
 

pikapig

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#13
Well, you also need to understand that at wide-angle, f/2.8 does not generate a very shallow DOF at all
Thanks:)

Go read more on DOF...

At different focal lengths as well as subject distance, you actually have quite a substantial window of sharpness...

Go look at my street shots, most of them are either shot at f2.8 or f1.8 when I am shooting with my 50mm lens.
Noted bro..but im asking more on dim lighting for a wide picture..will f2.8 be useful..

DOF from what I've learnt is factored by both aperture size and focal length. Try this website, Understanding Depth of Field in Photography. It's quite informative and technical (aka dry). :p

In my experience with my EFS 17-55, the shallow DOF out of f/2.8 is not a problem in indoor groupshots, due to the (wider) focal length required to fit everyone inside the frame. It gets more shallow only when you use the narrower end of the focal length.

For nightshooting of landscape, flash or stand is the logical approach, not aperture size. That's why I think the EFS10-22 (or most UWAs for that matter) is designed with f/3.5 widest.

Enjoy shooting! :)
Thanks for the link bro..its very helpful..thanks
 

pikapig

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#14
DOF will not be too shallow at F2.8

Dun forget the tamron lens is quite wide, the shallow DOF is only a problem for longer range.
Noted with thanks...
 

pikapig

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Aug 17, 2007
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#15
My question has been solved within an hr of posting...

thanks for the helpful replies.
 

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